Does the structure of consciousness mimic that of the visual process?

Does the structure of consciousness mimic that of the visual process?

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It seems to me that the structure of the conscious mind has some strong similarities to the way our visual field functions. The visual field has a strong and detailed focus at the center, and this is what generally commands our attention, while at the same time the visual resolution decreases outward from that center and its content occupies less of our attention, to the point that our peripheral vision will alert us to movements but has little to do with what we are recognizing consciously.

This is similar to the way we think. We have a central focus, which is the conscious thought, but that object of thought has many associations or links to other thought objects, and they form a ring around the focus, just out of view (ie. in the immediate unconscious zone). Those primary associations also have their own associations that form a secondary ring, deeper into the unconscious, with further rings extending outward representing decreasing levels of action potential.

It makes sense to me that the conscious mind would be patterned on the functional model of the visual field which is much older and more fundamental.

Thus, my question: Does the structure of consciousness mimic that of the visual process?

You are describing an observation as old as Freud, where he divided human's experience into three levels, roughly along the same lines as you. The conscious as that clear and ill-defined concept that gives you the feeling of attention, awareness, and self. The preconscious as the level just outside of your current awareness but that could easily spring to your consciousness. Finally, the unconscious, which is a level that doesn't have an analogy in vision: it corresponds to experiences that cannot come to your consciousness but that still affect your behavior.

Unfortunately, this correspondence does not extend beyond analogy, for several reasons. From the point of view of introspection -- the oldest and arguably still only reliable method for studying consciousness -- it is not clear how you would distinguish the visual sensation of attending stimuli from the conscious. In particular, it is not at all clear that the experience you describe as visual is an artefact of the visual system and not consciousness itself. The reason to believe that this is a feature of consciousness and not the visual system is because you experience the same things for hearing, touch, and to-a-lesser-extent smell.

Moving onto the scientific basis is much more difficult, in particular, you write:

It makes sense to me that the conscious mind would be patterned on the functional model of the visual field which is much older and more fundamental.

This to me seems like an unjustified assertion. Although we have some neurological models of consciousness, none of them are at the level where where we can start to date them on an evolutionary scale.

Inner Speech


Inner speech constitutes a fundamental cognitive activity not limited to working memory (the phonological loop ) but including self-regulation (initiating, shaping, guiding, and controlling behavior), language functions, self-awareness (e.g., autobiographical memory, mental time travel), emotional release, task-switching, preparation for upcoming social encounters, and more. Various methods exist to measure inner speech, some easy to administer but limiting (e.g., questionnaires) and others more ecologically valid but time consuming (e.g., thought sampling). The general agreement is that inner speech is social in origin, it is preceded by private speech, and once internalized, it becomes mostly abbreviated and predicative. Although various brain regions underlie inner speech production, the LIFG seems to represent the most important area. Inner speech resembles a double-edged sword – on the one hand, it is associated with positive consequences such as self-regulation, yet on the other hand, negative and ruminative self-talk may lead to or maintain psychological disorders such as anxiety and depression. Inner speech, nonetheless, remains neglected compared to other important psychological concepts. To illustrate, what people actually talk to themselves about is largely unknown and current work is precisely aiming at answering that and other exciting research questions.


The human mind is predisposed to believe that physical objects, when unperceived, still exist with definite shapes and locations in space. The psychologist Piaget proposed that children start to develop this belief in “object permanence” around 9 months of age, and have it firmly entrenched just 9 months later (Piaget, 1954). Further studies suggest that object permanence starts as early as 3 months of age (Bower, 1974 Baillargeon and DeVos, 1991).

Belief in object permanence remains firmly entrenched into adulthood, even in the brightest of minds. Abraham Pais said of Einstein, “We often discussed his notions on objective reality. I recall that on one walk Einstein suddenly stopped, turned to me and asked whether I really believed that the moon exists only when I look at it” (Pais, 1979). Einstein was troubled by interpretations of quantum theory that entail that the moon does not exist when unperceived.

Belief in object permanence underlies physicalist theories of the mind-body problem. When Gerald Edelman claimed, for instance, that “There is now a vast amount of empirical evidence to support the idea that consciousness emerges from the organization and operation of the brain” he assumed that the brain exists when unperceived (Edelman, 2004). When Francis Crick asserted the 𠇊stonishing hypothesis” that “You're nothing but a pack of neurons” he assumed that neurons exist when unperceived (Crick, 1994).

Object permanence underlies the standard account of evolution by natural selection. As James memorably put it, “The point which as evolutionists we are bound to hold fast to is that all the new forms of being that make their appearance are really nothing more than results of the redistribution of the original and unchanging materials. The self-same atoms which, chaotically dispersed, made the nebula, now, jammed and temporarily caught in peculiar positions, form our brains” (James, 1890). Evolutionary theory, in the standard account, assumes that atoms, and the replicating molecules that they form, exist when unperceived.

Object permanence underlies computational models of the visual perception of objects. David Marr, for instance, claimed “We … very definitely do compute explicit properties of the real visible surfaces out there, and one interesting aspect of the evolution of visual systems is the gradual movement toward the difficult task of representing progressively more objective aspects of the visual world” (Marr, 1982). For Marr, objects and their surfaces exist when unperceived, and human vision has evolved to describe their objective properties.

Bayesian theories of vision assume object permanence. They model object perception as a process of statistical estimation of object properties, such as surface shape and reflectance, that exist when unperceived. As Alan Yuille and Heinrich Bülthoff put it, “We define vision as perceptual inference, the estimation of scene properties from an image or sequence of images … ” (Yuille and Bülthoff, 1996).

There is a long and interesting history of debate about which properties of objects exist when unperceived. Shape, size, and position usually make the list. Others, such as taste and color, often do not. Democritus, a contemporary of Socrates, famously claimed, 𠇋y convention sweet and by convention bitter, by convention hot, by convention cold, by convention color but in reality atoms and void” (Taylor, 1999).

Locke proposed that “primary qualities” of objects, such as 𠇋ulk, figure, or motion” exist when unperceived, but that “secondary properties” of objects, such as 𠇌olors and smells” do not. He then claimed that “… the ideas of primary qualities of bodies are resemblances of them, and their patterns do really exist in the bodies themselves, but the ideas produced in us by these secondary qualities have no resemblance of them at all” (Locke, 1690).

Philosophical and scientific debate continues to this day on whether properties such as color exist when unperceived (Byrne and Hilbert, 2003 Hoffman, 2006). But object permanence, certainly regarding shape and position, is so deeply assumed by the scientific literature in the fields of psychophysics and computational perception that it is rarely discussed.

It is also assumed in the scientific study of consciousness and the mind-body problem. Here the widely acknowledged failure to create a plausible theory forces reflection on basic assumptions, including object permanence. But few researchers in fact give it up. To the contrary, the accepted view is that aspects of neural dynamics𠅏rom quantum-gravity induced collapses of wavefunctions at microtubules (Hameroff, 1998) to informational properties of re-entrant thalamo-cortical loops (Tononi, 2004)�use, or give rise to, or are identical to, consciousness. As Colin McGinn puts it, “we know that brains are the de facto causal basis of consciousness, but we have, it seems, no understanding whatever of how this can be so” (McGinn, 1989).

The Science of Consciousness

This section gives an overview of experiments on the correlates of consciousness, which measure consciousness, measure the physical world and look for spatiotemporal structures that are correlated with conscious states. A number of assumptions are needed to handle the fact that a brain's consciousness can only be measured indirectly through first person reports, which can also be generated by systems that are not typically thought to be conscious, such as computers. It is also necessary to assume that consciousness cannot vary independently of our measurement of it, which would undermine our ability to study consciousness scientifically.

Measurement of Consciousness (C-Reports)

A full discussion of the best way to define consciousness is beyond the scope of this article. The working definition that I will use is that consciousness is the stream of experience that appears when we wake up in the morning and disappears when we fall into deep sleep at night. This can have different levels of intensity (from drowsy to hyper alert) and a wide variety of contents. We cannot directly detect the consciousness of another person, and so a variety of external behaviors are used to infer the presence of conscious states.

When I say “I am conscious” I am stating that I can see objects distributed in space around me, that I can hear, smell and touch these objects and attend to different aspects of them. A report of a conscious experience can be spoken, written down, or expressed as a set of responses to yes/no questions𠅏or example, when patients communicate by imagining playing tennis or walking around a house in an fMRI scanner (Monti et al., 2010) 2 . People can be asked to subjectively assess the clarity of their visual experience (Ramsøy and Overgaard, 2004), and their level of awareness of a stimulus can be extracted using indirect measures, such as post-decision wagering (Persaud et al., 2007) 3 .

When people are not explicitly reporting their consciousness they can still be considered to be conscious on the basis of their external behavior. For example, Shanahan (2010) has argued that enhanced flexibility in the face of novelty and the ability to inwardly execute a sequence of problem-solving steps are a sign of consciousness, and the Glasgow Coma Scale uses motor responsiveness, verbal performance and eye opening to measure the level of consciousness in patients (Teasdale and Jennett, 1974). An overview of some of the different techniques for measuring consciousness is given by Seth et al. (2008).

I will use 𠇌-report” to designate any form of external behavior that is interpreted as a report about the level and/or contents of consciousness. This paper will primarily focus on verbal c-reporting, on the assumption that similar arguments can be applied to any form of behavioral report about consciousness. C-reporting will be interpreted in the fullest possible sense, so that every possible detail of a conscious experience that could be reported will be assumed to be reported.

One of the key problems with c-reporting is that it is hard to obtain accurate detailed descriptions of conscious states. Consciousness changes several times per second and it is altered by the act of c-reporting, so how can we describe it using natural language, which operates on a time scale of seconds? Shanahan (2010) has suggested that this problem could be addressed by resetting our consciousness, so that multiple probes can be run on a single fixed state (see section Platinum Standard Systems). People can also be trained to make more accurate reports about their consciousness (Lutz et al., 2002), and there has been a substantial amount of work on the use of interviews to help people describe their conscious states 4 . These problems have led to a debate about the extent to which we can generate accurate descriptions of our consciousness (Hurlburt and Schwitzgebel, 2007).

C-reports are typically transformed into natural language descriptions of a state of consciousness. However, natural language is not ideal for describing consciousness because it is context-dependent, ambiguous and it cannot be used to describe the experiences of non-human systems (Chrisley, 1995). It is also difficult to see how natural language descriptions could be incorporated into mathematical theories of consciousness. One way of addressing these problems would be to use a tightly structured formal language to describe consciousness (Gamez, 2006). Chrisley (1995) has made some suggestions about how consciousness can be described using robotic systems, although it is not clear to what extent these proposals could be play a role in a mathematical theory of consciousness.

Measurement of Unconscious Information (Uc-Reports)

The absence of a c-report about the level and/or contents of consciousness is typically taken as a sign that a person is unconscious or that a particular piece of information in the brain is unconscious. People can also make deliberate reports of unconscious mental content. For example, forced choice guessing is used in psychology experiments to measure unconscious mental content and visually guided reaching behavior in blindsight patients is interpreted as a sign that they have access to unconscious visual information. Galvanic skin responses can indicate that information is being processed unconsciously (Kotze and Moller, 1990) and priming effects can be used to determine if words are being processed unconsciously𠅏or example, Merikle and Daneman (1996) played words to patients under general anesthesia and found that when they were awake they often completed word stems with words that they had heard unconsciously.

All of these types of unconscious reporting will be referred to as “uc-reports,” which are any form of positive or negative behavioral output that is interpreted as the absence of consciousness or the presence of unconscious information. While there will inevitably be gray areas between c-reports and uc-reports, it will be assumed that there are enough clear examples of both types to justify the distinction in this paper.

Platinum Standard Systems

To scientifically study consciousness we need to start with a physical system that is commonly agreed to be capable of consciousness and whose c-reports can be believed to be about consciousness. The typical approach that is taken in empirical work on consciousness is to set aside philosophical worries about solipsism and zombies, and make the assumption that the human brain is capable of consciousness. This assumption can be made more general by introducing the notion of a platinum standard system, which is defined as follows 5 :

D1. A platinum standard system is a physical system that is assumed to be associated with consciousness some or all of the time.

By 𠇊ssociated” it is meant that consciousness is linked to a platinum standard system, but no claims are being made about causation or metaphysical identity. With this definition in place, we can make the explicit assumption that the human brain is a platinum standard system 6 :

A1. The normally functioning adult human brain is a platinum standard system.

By “normally functioning” it is meant that the brain is alive, that it would be certified as normally functioning by a doctor, and that it does not contain any unusual chemicals that might affect its operation 7 . While the normally functioning adult human brain is currently the only system that is confidently associated with consciousness, further assumptions could be added to extend the number of platinum standard systems𠅏or example, claiming that infant, monkey or alien brains are associated with consciousness.

A second issue in consciousness research is the possibility that two platinum standard systems in similar states could be associated with radically different consciousnesses while manifesting the same behavior. For example, there is the classic problem of color inversion, according to which I might experience red when my brain is in a particular state, you might experience green, and we could both use 𠇋lue” to describe our conscious states. More complicated situations can be imagined𠅏or instance, my consciousness of having a bath could be remapped onto a behavioral output that controls an airplane. If consciousness can vary independently of the physical world, then it will be impossible to systematically study the relationship between consciousness and the physical world.

A simple way of addressing this issue is to assume that consciousness supervenes on the physical world. Since we are only concerned with developing a pragmatic approach to the science of consciousness, it is not necessary to assume that consciousness logically or metaphysically supervenes on the brain—we just need to assume that the natural laws are such that consciousness cannot vary independently of the physical world:

A2. The consciousness associated with a platinum standard system nomologically supervenes on the platinum standard system. In our current universe physically identical platinum standard systems are associated with identical consciousness.

The c-reports that are used to measure consciousness can be cross-checked against each other for consistency, but there is no ultimate way of establishing whether a set of c-reports from a platinum standard system correspond to the consciousness that is associated with the platinum standard system. Since c-reports are the only way in which consciousness can be scientifically measured, it has to be explicitly assumed that c-reports from a platinum standard system co-vary with its consciousness:

A3. During an experiment on the correlates of consciousness, the consciousness associated with a platinum standard system is functionally connected to its c-reports about consciousness.

A3 captures the idea that when we make a c-report about consciousness, what we say about consciousness has some correspondence with the consciousness that is being c-reported. The functional connectivity means that the link between consciousness and c-reports is a deviation from statistical independence, not a causal connection 8 . A3 does not specify the amount of functional connectivity between consciousness and the c-reports, which might be quite low because of the limits of the c-reporting methods. A3 is also explicitly restricted to experimental work, which leaves open the possibility that predictions could be made about consciousness in situations in which c-reporting is disconnected from consciousness.

A contrastive experiment that compares the states of the conscious and unconscious brain is meaningless if the apparently unconscious brain is actually conscious but unable to report or remember its consciousness. Similarly, a binocular rivalry experiment on consciousness is worthless if the apparently unconscious information is associated with a separate consciousness that is disconnected from the memory and/or reporting systems. Ghostly ecosystems of unreportable consciousnesses would completely undermine all contrastive experiments on consciousness—scientific studies can only proceed on the assumption that they do not exist:

A4. During an experiment on the correlates of consciousness all conscious states associated with a platinum standard system are available for c-reports about consciousness.

A4 assumes that all conscious states in a platinum standard system are available for c-report, even if they are not actually reported during an experiment 9 . This makes it possible to use a variety of c-reports to extract a complete picture of the consciousness associated with a particular state of a platinum standard system. To circumvent the problems of limited working memory it might be necessary to put the system into a particular state, run the probe, reset the system and apply a different probe, until all of the data about consciousness has been extracted 10 .

Assumption A4 is explicitly limited to experiments on the correlates of consciousness. During these experiments it is assumed that the consciousness that is present in the system can be measured, which is a condition of possibility for this type of experimental work. While phenomenal consciousness and access 𠇌onsciousness” might be conceptually dissociable (Block, 1995) 11 , the idea that non-measureable phenomenal consciousness could be present during experiments on the correlates of consciousness is, from the perspective of this paper, incompatible with the scientific study of the correlates of consciousness. A4 is also incompatible with panpsychism, which claims that apparently unconscious parts of the brain and body are associated with an inaccessible consciousness. For similar reasons A4 is likely to be incompatible with Zeki and Bartels' (1999) proposal that micro-consciousnesses are distributed throughout the brain. Outside of experiments on the correlates of consciousness it is possible, even likely, that there could be inaccessible phenomenal consciousness. Information gathered by experiments on the correlates of consciousness could be used to make predictions about the presence of phenomenal consciousness in these situations𠅏or example, it could be used to make predictions about consciousness in brain damaged patients, infants or animals.

Correlations Between Consciousness and the Physical World

In this paper, the correlates of consciousness are defined in a similar way to Chalmers' (2000) definition of the total correlates of consciousness 12 :

D2. A correlate of a conscious experience, e1, is a minimal set of one or more spatiotemporal structures in the physical world. This set is present when e1 is present and absent when e1 is absent.

The notion of a minimal set is intended to exclude features of a platinum standard system that typically occur at the same time as consciousness, but whose removal would not lead to the alteration or loss of consciousness. For example, the correlates of consciousness in the brain might have prerequisites and consequences (see section Separating out the Correlates of Consciousness) that would typically co-occur with consciousness, but the brain would be conscious in exactly the same way if the minimal set of correlates could be induced without these prerequisites and consequences. Correlates defined according to D2 would continue to be associated with consciousness if they were extracted from the brain or implemented in an artificial system. I have excluded terms like “necessity” and “sufficiency” from D2 because they could imply that the physical brain causes consciousness, which is not required for a strictly correlations-based approach 13 . “Spatiotemporal structures” is a deliberately vague term that captures anything that might be correlated with consciousness, such as activity in brain areas, neural synchronization, electromagnetic waves, quantum events, etc. The minimal set of spatiotemporal structures can be established by systematic experiments in which all possible combinations of candidate features are considered (see Table 1). An experiment on the correlates of consciousness is illustrated in Figure 1.

Table 1. Illustrative example of correlations that could exist between conscious experiences (e1 and e2) and a physical system.

Figure 1. Experiment on the correlates of consciousness. The normally functioning adult human brain is assumed to be a platinum standard system that is associated with consciousness (D1 and A1). All of this system's conscious states are available for c-reports (A4), which are functionally connected to its conscious states (A3). Correlations are identified between the spatiotemporal structures in the platinum standard system and the c-reports about consciousness 14 .

While there has been an extensive amount of work on the neural correlates of consciousness, it has not been demonstrated that consciousness is only correlated with activity in biological neurons. It is possible that spatiotemporal structures in other components of the brain, such as hemoglobin or glia, are correlated with consciousness as well. To fully understand the relationship between consciousness and the physical world we need to consider all possible spatiotemporal structures in a platinum standard system that might be correlated with consciousness (Gamez, 2012).

Definition D2 enables me to state assumption A2 more precisely:

A2a. The consciousness associated with a platinum standard system nomologically supervenes on the correlates of consciousness in the platinum standard system. In our current universe the spatiotemporal structures that correlate with conscious experience e1 will be associated with e1 wherever they are found.

Finally, since the correlates of consciousness are not statistically independent from a platinum standard system's consciousness, they can also be described as features of a platinum standard system that are functionally connected to its conscious states. This way of describing the relationship between consciousness and the physical brain will play a role in what follows, and so it will be formally stated as lemma 1:

L1. There is a functional connection between consciousness and the correlates of consciousness.

Stream of consciousness

In literary criticism, stream of consciousness is a narrative mode or method that attempts "to depict the multitudinous thoughts and feelings which [sic] pass through the mind" of a narrator. [1] The term was coined by Alexander Bain in 1855 in the first edition of The Senses and the Intellect, when he wrote, "The concurrence of Sensations in one common stream of consciousness (on the same cerebral highway) enables those of different senses to be associated as readily as the sensations of the same sense" (p. 359). [2] But it is commonly credited to William James who used it in 1890 in his The Principles of Psychology. In 1918, the novelist May Sinclair (1863–1946) first applied the term stream of consciousness, in a literary context, when discussing Dorothy Richardson's (1873–1957) novels. [3] Pointed Roofs (1915), the first work in Richardson's series of 13 semi-autobiographical novels titled Pilgrimage, [4] is the first complete stream-of-consciousness novel published in English. However, in 1934, Richardson comments that "Proust, James Joyce, Virginia Woolf & D.R. . were all using 'the new method', though very differently, simultaneously". [5] There were, however, many earlier precursors and the technique is still used by contemporary writers.

Does the structure of consciousness mimic that of the visual process? - Psychology

Freudian dream interpretation

Activation-synthesis dream theory

Information-processing dream theory

Dissociation theory of hypnosis

Hallucinogens (also called psychedelics)

While you are reading this text, you can probably become aware of your sense of consciousness. Early psychologists such as William James, author of the first psychology textbook, were very interested in consciousness. However, since no tools existed to examine it scientifically, the study of consciousness faded for a time. Currently, consciousness is becoming a more common research area due to more sophisticated brain imaging tools and an increased emphasis on cognitive psychology.

The historical discussion about consciousness centers on the competing philosophical theories of dualism and monism. Dualists believe humans (and the universe in general) consist of two materials: thought and matter. Matter is everything that has substance. Thought is a nonmaterial aspect that arises from, but is in some way independent of, a brain. Dualists argue that thought gives humans free will. Some philosophers maintain that thought is eternal and continues existing after the brain and body die. Monists disagree and believe everything is the same substance, and thought and matter are aspects of the same substance. Thought is a by-product of brain processes and stops existing when the body dies.

Psychology does not try to address these metaphysical questions directly. However, psychologists are trying to examine what we can know about consciousness and to describe some of the processes or elements of consciousness. Psychologists define consciousness as our level of awareness about ourselves and our environment. We are conscious to the degree we are aware of what is going on inside and outside ourselves.

This psychological definition implies that consciousness is not like an on/off switch. We are not conscious or unconscious. Psychologists refer to different levels and different states of consciousness.


Ironically, we experience different levels of consciousness in our daily life without being consciously aware of the experience. While you are reading this text, you might be tapping your pen or moving your leg in time to the music you are listening to. One level of consciousness is controlling your pen or leg, while another level is focused on reading these words. Research demonstrates other more subtle and complex effects of different levels of consciousness. The mere-exposure effect (also see Chapter 14) occurs when we prefer stimuli we have seen before over novel stimuli, even if we do not consciously remember seeing the old stimuli. For example, say a researcher shows a group of research participants a list of nonsense terms for a short period of time. Later, the same group is shown another list of terms and asked which terms they prefer or like best. The mere-exposure effect predicts that the group will choose the terms they saw previously, even though the group could not recall the first list of nonsense terms if asked. On some level, the group knows the first list.

A closely related concept is priming. Research participants respond more quickly and/or accurately to questions they have seen before, even if they do not remember seeing them. Another fascinating phenomenon that demonstrates levels of consciousness is blind sight. Some people who report being blind can nonetheless accurately describe the path of a moving object or accurately grasp objects they say they cannot see! One level of their consciousness is not getting any visual information, while another level is able to “see” as demonstrated by their behavior.

The concept of consciousness consisting of different levels or layers is well established. Not all researchers agree about what the specific levels are, but some of the possible types offered by researchers are shown in the following.

The information about yourself and your environment you are currently aware of. Your conscious level right now is probably focusing on these words and their meanings.

Body processes controlled by your mind that we are not usually (or ever) aware of. Right now, your nonconscious is controlling your heartbeat, respiration, digestion, and so on.

Information about yourself or your environment that you are not currently thinking about (not in your conscious level) but you could be. If I asked you to remember your favorite toy as a child, you could bring that preconscious memory into your conscious level.

Information that we are not consciously aware of but we know must exist due to behavior. The behaviors demonstrated in examples of priming and mere-exposure effect suggest some information is accessible to this level of consciousness but not to our conscious level.

Psychoanalytic psychologists believe some events and feelings are unacceptable to our conscious mind and are repressed into the unconscious mind. Many psychologists object to this concept as difficult or impossible to prove. See the section on psychoanalytic theory in Chapter 10 for more information about the unconscious.

As a student, sleep is most likely a subject near and dear to your heart. Many studies show that a large percentage of high school and college students are sleep deprived, meaning they do not get as much sleep as their body wants. To a psychologist, referring to being asleep as being unconscious is incorrect. Sleep is one of the states of consciousness.

According to the psychological definition of consciousness, sleep is a state of consciousness because, while we are asleep, we are less aware of ourselves and our environment than we are when we are in our normal awake state. Other states of consciousness&mdashdrug-induced states, hypnosis, and so on&mdashare states of consciousness for similar reasons.

Sleep Cycle

You may be familiar with the term circadian rhythm. During a 24-hour day, our metabolic and thought processes follow a certain pattern. Some of us are more active in the morning than others, some of us get hungry or go to the bathroom at certain times of day, and so on. Part of our circadian rhythm is our sleep cycle. Our sleep cycle is our typical pattern of sleep. Researchers using EEG machines can record how active our brains are during sleep and describe the different stages of sleep we progress through each night. Refer to Figure 5.1 for a graphic representation of the stages of a typical sleep cycle.

As you can see in Figure 5.1, sleep is far from being a time of unconsciousness. We cycle through different stages of sleep during the night. Our brain waves and level of awareness change as we cycle through the stages. The period when we are falling asleep is called sleep onset. This is the stage between wakefulness and sleep. Our brain produces alpha waves when we are drowsy but awake. We might experience mild hallucinations (such as falling or rising) before actually falling asleep and entering stage 1. While we are awake and in stages 1 and 2, our brains produce theta waves, which are relatively high-frequency, low-amplitude waves. However, the theta waves get progressively slower and higher in amplitude as we go from wakefulness and through stages 1 and 2. In stage 2, the EEG starts to show sleep spindles, which are short bursts of rapid brain waves. From there, we move into stages 3 and 4, which are sometimes called delta sleep (also called slow-wave sleep) because of the delta waves that exist during these stages. The slower the wave (slow waves are low-frequency waves), the deeper the sleep and less aware we are of our environment. A person in delta sleep is very difficult to wake up. If you are awakened out of delta sleep, you may be very disoriented and groggy. Delta sleep seems to be very important in replenishing the body’s chemical supplies, releasing growth hormones in children, and fortifying our immune system. A person deprived of delta sleep will be more susceptible to illness and will feel physically tired. Increasing exercise will increase the amount of time we spend in stages 3 and 4.

After a period of time in delta sleep, our brain waves start to speed up and we go back through stages 3 and 2. However, as we reach stage 1, our brain produces a period of intense activity, our eyes dart back and forth, and many of our muscles may twitch repeatedly. This is REM&mdashrapid eye movement. This sleep stage is sometimes called paradoxical sleep since our brain waves appear as active and intense as they do when we are awake. The exact purposes of REM are not clear, but some effects are known. Dreams usually occur in REM sleep. (Dreams can occur in any stage of sleep, but it is far more likely that any detailed dream occurs in REM.) REM sleep deprivation interferes with memory. Individuals deprived of REM sleep will experience REM rebound&mdashexperiencing more and longer periods of REM&mdashthe next time they are allowed to sleep normally. The more stress we experience during the day, the longer our periods of REM sleep will be.

Notice in Figure 5.1 that not only do we cycle through these approximately 90-minute stages about 4–7 times during the night, the cycle itself varies during the night. As we get closer to morning (or whenever we naturally awaken), we spend more time in stages 1 and 2 and in REM sleep and less in stages 3 and 4. Also, age affects the pattern. Babies not only spend more total time sleeping than we do (up to 18 hours), they also spend more time in REM sleep. As we age, our total need for sleep declines as does the amount of time we spend in REM sleep. Although research has not answered all the questions about sleep, details about our sleep cycle provide clues as to why we spend so much of our life in this altered state of consciousness.

Figure 5.1. Stages of sleep.

Sleep Disorders

Many of us will experience a night, or perhaps a series of nights, of sleeplessness. These isolated periods of disruption in our sleep pattern give us an idea of the inconvenience and discomfort true sleep disorders can cause in people’s lives. Sleep researchers identify and diagnose several sleep disorders.

Insomnia is far and away the most common sleep disorder, affecting up to 10 percent of the population. An insomniac has persistent problems getting to sleep or staying asleep at night. Most people will experience occasional bouts of insomnia, but diagnosed insomniacs have problems getting to sleep more often than not. Insomnia is usually treated with suggestions for changes in 'text-align: justifyline-height:normal'>Narcolepsy occurs far more rarely than insomnia, occurring in less than 0.001 percent of the population. Narcoleptics suffer from periods of intense sleepiness and may fall asleep at unpredictable and inappropriate times. Narcoleptics may suddenly fall into REM sleep regardless of what they are doing at the time. One of my students suffered from narcolepsy from the time he was a preadolescent up until his graduation from high school. After he was finally diagnosed, he estimated that before his treatment he was drowsy almost his entire day except for two to three hours in the late afternoon. Narcolepsy can be successfully treated with medication and changing sleep patterns (usually involving naps at certain times of the day).

Sleep apnea may occur almost as commonly as insomnia and in some ways might be more serious. Apnea causes a person to stop breathing for short periods of time during the night. The body causes the person to wake up slightly and gasp for air, and then sleep continues. This process robs the person of deep sleep and causes tiredness and possible interference with attention and memory. Severe apnea can be fatal. Since these individuals do not remember waking up during the night, apnea frequently goes undiagnosed. Overweight men are at a higher risk for apnea. Apnea can be treated with a respiration machine that provides air for the person as he or she sleeps.

My mother tells me that I experienced night terrors as a child. I would sit up in bed in the middle of the night and scream and move around my room. Night terrors usually affect children, and most do not remember the episode when they wake up. The exact causes are not known, but night terrors are probably related in some way to somnambulism (sleep walking). They occur more commonly in children, and both phenomena occur during the first few hours of the night in stage 4 sleep. Most people stop having night terrors and episodes of somnambulism as they get older.

Dreams are the series of storylike images we experience as we sleep. Some people remember dreams frequently, sometimes more than one per night, while others are not aware of whether we dream or not. Some of us even report lucid dreams in which we are aware that we are dreaming and can control the storyline of the dream. Dreams are a difficult research area for psychologists because they rely almost entirely on self-reports. As mentioned previously, researchers know that if people are awakened during or shortly after an REM episode, they often report they were dreaming. Researchers theorize about the purposes and meanings of dreams. However, validating these theories is difficult with the limited access researchers currently have to dreams.

Sigmund Freud considered dreams an important tool in his therapy. Freudian psychoanalysis emphasizes dream interpretation as a method to uncover the repressed information in the unconscious mind. Freud said that dreams were wish fulfilling, meaning that in our dreams we act out our unconscious desires. This type of dream analysis emphasizes two levels of dream content. Manifest content is the literal content of our dreams. If you dream about showing up at school naked, the manifest content is your nudity, the room you see yourself in at school, the people present, and so on. More important to Freud was the latent content, which is the unconscious meaning of the manifest content. Freud thought that even during sleep, our ego protected us from the material in the unconscious mind (thus the term protected sleep) by presenting these repressed desires in the form of symbols. So showing up naked at school would represent a symbol in this type of analysis, perhaps of vulnerability or anxiety. This type of dream analysis is common. Check any bookstore, and you will find multiple dream interpretation books based on this theory. However, popularity does not imply validity. Researchers point out that this theory is difficult to validate or invalidate. How do we know which are the correct symbols to examine and what they mean? The validity of the theory cannot be tested. Consequently, this analysis is mostly used in psychoanalytic therapy and in pop psychology rather than in research.

The activation-synthesis theory of dreaming looks at dreams first as biological phenomena. Brain imaging proves that our brain is very active during REM sleep. This theory proposes that perhaps dreams are nothing more than the brain’s interpretations of what is happening physiologically during REM sleep. Researchers know that our minds are very good at explaining events, even when the events have a purely physiological cause. Split-brain patients (see Chapter 3) sometimes make up elaborate explanations for behaviors caused by their operation. Dreams may be a story made up by a literary part of our mind caused by the intense brain activity during REM sleep. According to this theory, dreams, while interesting, have no more meaning than any other physiological reflex in our body.

The information-processing theory of dreaming falls somewhere in between the Freudian and activation-synthesis theories. This theory points out that stress during the day will increase the number and intensity of dreams during the night. Also, most people report their dream content relates somehow to daily concerns. Proponents of information processing theorize that perhaps the brain is dealing with daily stress and information during REM dreams. The function of REM may be to integrate the information processed during the day into our memories. Babies may need more REM sleep than adults because they process so much new information every day.

The high school where I teach usually hires a stage hypnotist to entertain at the postprom party. The day after students see the hypnotist’s show, I can expect dozens of questions about the process of hypnosis and whether it is a valid psychological phenomenon or some sort of trick. Many of the questions concern some of the curious powers hypnotism seems to have. One of these is posthypnotic amnesia, when people report forgetting events that occurred while they were hypnotized. The hypnotist may also implant a posthypnotic suggestion, a suggestion that a hypnotized person behave in a certain way after he or she is brought out of hypnosis. Like many other topics regarding consciousness, many questions about hypnosis are not completely answered. However, at least three theories attempt to explain what goes on during hypnosis.

Role theory states that hypnosis is not an alternate state of consciousness at all. This theory points out that some people are more easily hypnotized than others, a characteristic called hypnotic suggestibility. People with high hypnotic suggestibility share some other characteristics as well. They tend to have richer fantasy lives, follow directions well, and be able to focus intensely on a single task for a long period of time. These factors may indicate that hypnotism is a social phenomenon. Perhaps during hypnosis, people are acting out the role of a hypnotized person and following the suggestions of the hypnotist because that is what is expected of the role.

Other researchers use state theory to explain hypnosis. They point out that hypnosis meets some parts of the definition for an altered state of consciousness. Hypnotists seem to be able to suggest that we become more or less aware of our environments. In addition, some people report dramatic health benefits from hypnosis, such as pain control and reduction in specific physical ailments.

Researcher Ernest Hilgard explained hypnosis in a different way in his dissociation theory. According to Hilgard, hypnosis causes us to divide our consciousness voluntarily. One part or level of our consciousness responds to the suggestions of the hypnotist, while another part or level retains awareness of reality. In an experiment investigating hypnotism and pain control, Hilgard asked hypnotized participants to put their arm in an ice water bath. Most of us would feel this intense cold as painful after a few seconds, but the hypnotized participants reported no pain. However, when Hilgard asked them to lift their index finger if any part of them felt the pain, most participants lifted their finger. This experiment demonstrated the presence of a hidden observer, a part or level of our consciousness that monitors what is happening while another level obeys the hypnotist’s suggestions.

Psychoactive drugs are chemicals that change the chemistry of the brain (and the rest of the body) and induce an altered state of consciousness. Some of the behavioral and cognitive changes caused by these drugs are due to physiological processes, but some are due to expectations about the drug. Research shows that people will often exhibit some of the expected effects of the drug if they think they ingested it, even if they did not (this is similar to the placebo effect).

All psychoactive drugs change our consciousness through similar physiological processes in the brain. Normally, the brain is protected from harmful chemicals in the bloodstream by thicker walls surrounding the brain’s blood vessels. This is called the blood-brain barrier. However, the molecules that make up psychoactive drugs are small enough to pass through the blood-brain barrier. These molecules either mimic or block naturally occurring neurotransmitters in the brain. The drugs that mimic neurotransmitters are called agonists. These drugs fit in the receptor sites on a neuron that normally receive the neurotransmitter and function as that neurotransmitter normally would. The drugs that block neurotransmitters are called antagonists. These molecules also fit into receptor sites on a neuron. However, instead of acting like the neurotransmitter, they simply prevent the natural neurotransmitters from using that receptor site. Other drugs prevent natural neurotransmitters from being reabsorbed back into a neuron, creating an abundance of that neurotransmitter in the synapse. No matter what mechanism they use, drugs gradually alter the natural levels of neurotransmitters in the brain. The brain will produce less of a specific neurotransmitter if it is being artificially supplied by a psychoactive drug.

This change causes tolerance, a physiological change that produces a need for more of the same drug in order to achieve the same effect. Tolerance will eventually cause withdrawal symptoms in users. Withdrawal symptoms vary from drug to drug. They range from the headache I might get if I do not consume any caffeine during the day to the dehydrating and potentially fatal night sweats (sweating profusely during sleep) a heroin addict experiences during withdrawal. Dependence on psychoactive drugs can be either psychological or physical or can be both. Persons psychologically dependent on a drug feel an intense desire for the drug because they are convinced they need it in order to perform or feel a certain way. Persons physically dependent on a substance have a tolerance for the drug, experience withdrawal symptoms without it, and need the drug to avoid the withdrawal symptoms. Different researchers categorize psychoactive drugs in different ways, but four common categories are stimulants, depressants, hallucinogens, and opiates.

Caffeine, cocaine, amphetamines, and nicotine are common stimulants. Stimulants speed up body processes, including autonomic nervous system functions such as heart and respiration rate. This dramatic increase is accompanied by a sense of euphoria. The more-powerful stimulants, such as cocaine, produce an extreme euphoric rush that may make a user feel extremely self-confident and invincible. All stimulants produce tolerance, withdrawal effects, and other side effects (such as disturbed sleep, reduced appetite, increased anxiety, and heart problems) to a greater or lesser degree that corresponds with the power of the drug.

Depressants slow down the same body systems that stimulants speed up. Alcohol, barbiturates, and anxiolytics (also called tranquilizers or antianxiety drugs) like Valium are common depressants. Obviously, alcohol is by far the most commonly used depressant and psychoactive drug. A euphoria accompanies the depressing effects of depressants, as does tolerance and withdrawal symptoms. In addition, alcohol slows down our reactions and judgment by slowing down brain processes. The inhibition of different brain regions causes behavioral changes. For example, when enough alcohol is ingested to affect the cerebellum, our motor coordination is dramatically affected, eventually making it difficult or impossible for the user to even stand. Because it is so widespread, more research has been done on alcohol than on any other psychoactive drug.

Alcohol is categorized as a depressant because of its effect on our nervous system, even though some people report feeling more energized after ingesting a small amount of alcohol. This energizing effect is due to expectations about alcohol and because alcohol lowers inhibitions. Similarly, nicotine is a stimulant because it speeds up our nervous system, but some smokers smoke to relax.

Hallucinogens (also sometimes called psychedelics) do not necessarily speed up or slow down the body. These drugs cause changes in perceptions of reality, including sensory hallucinations, loss of identity, and vivid fantasies. Common hallucinogens include LSD, peyote, psilocybin mushrooms, and marijuana. One notable feature of hallucinogens is their persistence. Some amount of these drugs may remain in the body for weeks. If an individual ingests the hallucinogen again during this time period, the new dose of the chemical is added to the lingering amount, creating more profound and potentially dangerous effects. This effect is sometimes called reverse tolerance because the second dose may be less than the first but cause the same or greater effects. Effects of hallucinogens are less predictable than those of stimulants or depressants.

Opiates such as morphine, heroin, methadone, and codeine are all similar in chemical structure to opium, a drug derived from the poppy plant. The opiates all act as agonists for endorphins and thus are powerful painkillers and mood elevators. Opiates cause drowsiness and a euphoria associated with elevated endorphin levels. The opiates are some of the most physically addictive drugs because they rapidly change brain chemistry and create tolerance and withdrawal symptoms.


Directions: Each of the questions or incomplete statements below is followed by five suggested answers or completions. Select the one that is best in each case.

1.Agonists are psychoactive drugs that

(A)produce tolerance to the drug without the associated withdrawal symptoms.

(B)mimic and produce the same effect as certain neurotransmitters.

(C)mimic neurotransmitters and block their receptor sites.

(D)enhance the effects of certain opiates like heroin.

(E)make recovery from physical addiction more difficult.

2.In comparison with older people, babies

(A)sleep more fitfully they tend to wake up more often.

(B)sleep more deeply they spend more time in stage 3 and 4 sleep.

(C)spend more time in the REM stage than other sleep stages.

(D)spend more time in stage 1, which causes them to awaken easily.

(E)sleep more than young adults but less than people over 50.

3.Which of the following is the best analogy for how psychologists view consciousness?

(A)the on/off switch on a computer

(B)a circuit breaker that controls power to a house

(C)a fuse that allows electricity to pass through until a short circuit occurs

(D)a dimmer switch for a light fixture

(E)the ignition switch on a car

4.During a normal night’s sleep, how many times do we pass through the different stages of sleep?

5.Which of the following is evidence supporting the role theory of hypnosis?

(A)People with rich fantasy lives are more hypnotizable.

(B)People will not behave under hypnosis in ways they would not without hypnosis.

(C)Hilgard’s experiment demonstrated the presence of a hidden observer.

(D)Our heart and respiration rates may differ while under hypnosis.

(E)Some therapists successfully use hypnosis in therapy.

6.Activation-synthesis theory tries to explain

(A)how consciousness emerges out of neural firings.

(B)how psychoactive drugs create euphoric effects.

(C)the origin and function of dreams.

(D)how our mind awakens us after we pass through all the sleep stages.

(E)how our consciousness synthesizes all the sensory information it receives.

7.Hilgard’s experiment that demonstrated the presence of a hidden observer is evidence for which theory?

(B)levels theory of consciousness

(C)recuperative theory of sleep

(D)dissociation theory of hypnosis

(E)state theory of hypnosis

8.Which of the following two sleep disorders occur most commonly?

(D)somnambulism and insomnia

9.Marijuana falls under what category of psychoactive drug?

10.Night terrors and somnambulism usually occur during which stage of sleep?

(A)stage 1, close to wakefulness

(C)REM sleep, but only later in the night when nightmares usually occur

11.Which neurotransmitter is affected by opiates?

12.In the context of this unit, the term tolerance refers to

(A)treatment of psychoactive drug addicts by peers and other members of society.

(B)the amount of sleep a person needs to function normally.

(C)the need for an elevated dose of a drug in order to get the same effect.

(D)the labeling of individuals automatically produced by the level of our consciousness.

(E)the harmful side effects of psychoactive drugs.

13.The information-processing theory says that dreams

(A)are meaningless by-products of how our brains process information during REM sleep.

(B)are symbolic representations of the information we encode during the day.

(C)are processed by one level of consciousness but other levels remain unaware of the dreams.

(D)occur during REM sleep as the brain deals with daily stress and events.

(E)occur only after stressful events, explaining why some people never dream.

14.Which level of consciousness controls involuntary body processes?

15.Professor Bohkle shows a group of participants a set of geometric shapes for a short period of time. Later, Professor Bohkle shows the same group a larger set of shapes that includes the first set of geometric shapes randomly distributed among the other new images. When asked which shapes they prefer, the participants choose shapes from the first group more often than the new images, even though they cannot remember which images they had seen previously. This experiment demonstrates which concept?

Extension of Neural Darwinism to Consciousness

As we have seen, the anatomy of the thalamocortical system provides an essential element in the neural mechanism underlying consciousness. A characteristic feature of the cerebral cortex is the presence of corticocortical connections linking various neurons in spatially dispersed regions of the cortex to one another in a reciprocal fashion (Fuster, 2008). Similarly, the thalamus projects a large number of axons to all areas of the cortex, and the cortex projects an even larger number to the thalamus (Jones, 2007). Together the corticocortical, corticothalamic, and thalamocortical connections provide a necessary structural basis for dynamic reentry, the ongoing reciprocal signaling within the cortex and between the cortex and the thalamus, constituting a Dynamic Core (Edelman and Tononi, 2000). Reentrant coupling can result in the formation of synchronous time-locked patterns of activity essential to connecting and integrating the distinctive functions of different brain areas. Reentrant activity allows a brain area having responses originally evoked by sensory input to give similar responses in the absence of that input. By this means the brain “speaks to itself,” a necessary basis for memory and thought.

We have proposed earlier (Edelman, 1989) that reentry between posterior, modality-specific cortical areas and more anterior areas related to memory and executive functions provides a mechanism for conscious processes. The observation that this Dynamic Core (Edelman and Tononi, 2000) necessarily involves integration of activity in widespread distributed cortical areas accords with the concept of a Global Workspace. Experimental evidence for a role for a Dynamic Core of cortical reentrant activity in conscious perception has been provided by studies of electromagnetic signals generated in the brains of subjects viewing two different, fluctuating stimuli, one in each eye (Srinivasan et al., 1999). At any time, the subject exhibits binocular rivalry, i.e., is conscious of only one percept this alternates to the other percept every few seconds. As illustrated in Figure 1, conscious perception of a stimulus is correlated with enhanced coherence among signals from multiple distant cortical areas constituting a Global Workspace. Presumably this synchrony is generated and maintained by the reentrant neural activity that contributes to the Dynamic Core.

Figure 1. Results of a study of human whole-head magnetoencephalographic (MEG) signals evoked by visual stimuli that were binocularly rivalrous and frequency-tagged (Srinivasan et al., 1999). The topographic map indicates the magnitude of the MEG signal power at the frequency of the perceptually conscious dominant stimulus minus that at the same frequency when the same stimulus was non-dominant and non-conscious. Conscious perception of a stimulus was associated with a significant increase in the calculated coherence between distant MEG channels at the frequency of the perceived stimulus. Pairs of MEG channels whose coherence changed with change in percept are connected in the figure by cyan straight lines. These data point to a role for increased synchrony among distinct and distant neuronal groups in the Global Workspace during conscious perception. Presumably, these widespread groups constituting the Workspace contribute to the Dynamic Core.

Hierarchical recursive mapping by means of reentrant interactions in the Dynamic Core provides a mechanism for the integration of diverse neural signals from widespread cortical areas that give rise to such integrated patterns of neural activity. At any given moment, a process of integration of collective neuronal activity generates an interwoven pattern of responses unique to a particular animal at that particular moment of time (Edelman and Tononi, 2000).

Dynamic changes in the core lead to a linked sequence of discriminations. It has been proposed that the sequences of integrated activity in this discriminatory web give rise to the unitary conscious scenes that constitute phenomenal experience (Edelman, 1992). These temporal properties underlie what William James called the “stream of consciousness” (James, 1890). It has been suggested that a measure of the integration of information accounts for the presence of conscious experience (Tononi, 2005). However, no measure of integration alone can provide an exclusive account of the actual mechanisms that entail phenomenal conscious experience (Seth et al., 2006). Indeed, a number of other properties remain to be accounted for, requiring causal analysis of biological mechanisms. These include not only the temporal properties just mentioned, but also the intentionality or reference of conscious states (Brentano, 1973), as well as their modulation by attention (Knudsen, 2007).


It has been believed for some time that inputs from different sensory organs are processed in different areas in the brain, relating to systems neuroscience. Using functional neuroimaging, it can be seen that sensory-specific cortices are activated by different inputs. For example, regions in the occipital cortex are tied to vision and those on the superior temporal gyrus are recipients of auditory inputs. There exist studies suggesting deeper multisensory convergences than those at the sensory-specific cortices, which were listed earlier. This convergence of multiple sensory modalities is known as multisensory integration.

Sensory processing deals with how the brain processes sensory input from multiple sensory modalities. These include the five classic senses of vision (sight), audition (hearing), tactile stimulation (touch), olfaction (smell), and gustation (taste). Other sensory modalities exist, for example the vestibular sense (balance and the sense of movement) and proprioception (the sense of knowing one's position in space) Along with Time (The sense of knowing where one is in time or activities). It is important that the information of these different sensory modalities must be relatable. The sensory inputs themselves are in different electrical signals, and in different contexts. [6] Through sensory processing, the brain can relate all sensory inputs into a coherent percept, upon which our interaction with the environment is ultimately based.

Basic structures involved Edit

The different senses were always thought to be controlled by separate lobes of the brain, [7] called projection areas. The lobes of the brain are the classifications that divide the brain both anatomically and functionally. [8] These lobes are the Frontal lobe, responsible for conscious thought, Parietal lobe, responsible for visuospatial processing, the Occipital lobe, responsible for the sense of sight, and the temporal lobe, responsible for the senses of smell and sound. From the earliest times of neurology, it has been thought that these lobes are solely responsible for their one sensory modality input. [9] However, newer research has shown that that may not entirely be the case.

Problems Edit

Sometimes there can be a problem with the encoding of the sensory information. This disorder is known as Sensory processing disorder (SPD). This disorder can be further classified into three main types. [10]

  • Sensory modulation disorder, in which patients seek sensory stimulation due to an over or under response to sensory stimuli.
  • Sensory based motor disorder. Patients have incorrect processing of motor information that leads to poor motor skills.
  • Sensory processing disorder or sensory discrimination disorder, which is characterized by postural control problems, lack of attentiveness, and disorganization.

There are several therapies used to treat SPD. Anna Jean Ayres claimed that a child needs a healthy "sensory diet," which is all of the activities that children engage in, that gives them the necessary sensory inputs that they need to get their brain into improving sensory processing.

In the 1930s, Dr. Wilder Penfield was conducting a very bizarre operation at the Montreal Neurological Institute. [11] Dr. Penfield "pioneered the incorporation of neurophysiological principles in the practice of neurosurgery. [4] [12] Dr. Penfield was interested in determining a solution to solve the epileptic seizure problems that his patients were having. He used an electrode to stimulate different regions of the brain's cortex, and would ask his still conscious patient what he or she felt. This process led to the publication of his book, The Cerebral Cortex of Man. The "mapping" of the sensations his patients felt led Dr. Penfield to chart out the sensations that were triggered by stimulating different cortical regions. [13] Mrs. H. P. Cantlie was the artist Dr. Penfield hired to illustrate his findings. The result was the conception of the first sensory Homunculus.

The Homonculus is a visual representation of the intensity of sensations derived from different parts of the body. Dr. Wilder Penfield and his colleague Herbert Jasper developed the Montreal procedure using an electrode to stimulate different parts of the brain to determine which parts were the cause of the epilepsy. This part could then be surgically removed or altered in order to regain optimal brain performance. While performing these tests, they discovered that the functional maps of the sensory and motor cortices were similar in all patients. Because of their novelty at the time, these Homonculi were hailed as the "E=mc² of Neuroscience". [11]

There are still no definitive answers to the questions regarding the relationship between functional and structural asymmetries in the brain. [14] There are a number of asymmetries in the human brain including how language is processed mainly in the left hemisphere of the brain. There have been some cases, however, in which individuals have comparable language skills to someone who uses his left hemisphere to process language, yet they mainly use their right or both hemispheres. These cases pose the possibility that function may not follow structure in some cognitive tasks. [14] Current research in the fields of sensory processing and multisensory integration is aiming to hopefully unlock the mysteries behind the concept of brain lateralization.

Research on sensory processing has much to offer towards understanding the function of the brain as a whole. The primary task of multisensory integration is to figure out and sort out the vast quantities of sensory information in the body through multiple sensory modalities. These modalities not only are not independent, but they are also quite complementary. Where one sensory modality may give information on one part of a situation, another modality can pick up other necessary information. Bringing this information together facilitates the better understanding of the physical world around us.

It may seem redundant that we are being provided with multiple sensory inputs about the same object, but that is not necessarily the case. This so-called "redundant" information is in fact verification that what we are experiencing is in fact happening. Perceptions of the world are based on models that we build of the world. Sensory information informs these models, but this information can also confuse the models. Sensory illusions occur when these models do not match up. For example, where our visual system may fool us in one case, our auditory system can bring us back to a ground reality. This prevents sensory misrepresentations, because through the combination of multiple sensory modalities, the model that we create is much more robust and gives a better assessment of the situation. Thinking about it logically, it is far easier to fool one sense than it is to simultaneously fool two or more senses.

One of the earliest sensations is the olfactory sensation. Evolutionary, gustation and olfaction developed together. This multisensory integration was necessary for early humans in order to ensure that they were receiving proper nutrition from their food, and also to make sure that they were not consuming poisonous materials. [ citation needed ] There are several other sensory integrations that developed early on in the human evolutionary time line. The integration between vision and audition was necessary for spatial mapping. Integration between vision and tactile sensations developed along with our finer motor skills including better hand-eye coordination. While humans developed into bipedal organisms, balance became exponentially more essential to survival. The multisensory integration between visual inputs, vestibular (balance) inputs, and proprioception inputs played an important role in our development into upright walkers.

Audiovisual system Edit

Perhaps one of the most studied sensory integrations is the relationship between vision and audition. [15] These two senses perceive the same objects in the world in different ways, and by combining the two, they help us understand this information better. [16] Vision dominates our perception of the world around us. This is because visual spatial information is one of the most reliable sensory modalities. Visual stimuli are recorded directly onto the retina, and there are few, if any, external distortions that provide incorrect information to the brain about the true location of an object. [17] Other spatial information is not as reliable as visual spatial information. For example, consider auditory spatial input. The location of an object can sometimes be determined solely on its sound, but the sensory input can easily be modified or altered, thus giving a less reliable spatial representation of the object. [18] Auditory information therefore is not spatially represented unlike visual stimuli. But once one has the spatial mapping from the visual information, multisensory integration helps bring the information from both the visual and auditory stimuli together to make a more robust mapping.

There have been studies done that show that a dynamic neural mechanism exists for matching the auditory and visual inputs from an event that stimulates multiple senses. [19] One example of this that has been observed is how the brain compensates for target distance. When you are speaking with someone or watching something happen, auditory and visual signals are not being processed concurrently, but they are perceived as being simultaneous. [20] This kind of multisensory integration can lead to slight misperceptions in the visual-auditory system in the form of the ventriloquist effect. [21] An example of the ventriloquism effect is when a person on the television appears to have his voice coming from his mouth, rather than the television's speakers. This occurs because of a pre-existing spatial representation within the brain which is programmed to think that voices come from another human's mouth. This then makes it so the visual response to the audio input is spatially misrepresented, and therefore misaligned.

Sensorimotor system Edit

Hand eye coordination is one example of sensory integration. In this case, we require a tight integration of what we visually perceive about an object, and what we tactilely perceive about that same object. If these two senses were not combined within the brain, then one would have less ability to manipulate an object. Eye–hand coordination is the tactile sensation in the context of the visual system. The visual system is very static, in that it doesn't move around much, but the hands and other parts used in tactile sensory collection can freely move around. This movement of the hands must be included in the mapping of both the tactile and visual sensations, otherwise one would not be able to comprehend where they were moving their hands, and what they were touching and looking at. An example of this happening is looking at an infant. The infant picks up objects and puts them in his mouth, or touches them to his feet or face. All of these actions are culminating to the formation of spatial maps in the brain and the realization that "Hey, that thing that's moving this object is actually a part of me." Seeing the same thing that they are feeling is a major step in the mapping that is required for infants to begin to realize that they can move their arms and interact with an object. This is the earliest and most explicit way of experiencing sensory integration.

In the future, research on sensory integration will be used to better understand how different sensory modalities are incorporated within the brain to help us perform even the simplest of tasks. For example, we do not currently have the understanding needed to comprehend how neural circuits transform sensory cues into changes in motor activities. More research done on the sensorimotor system can help understand how these movements are controlled. [22] This understanding can potentially be used to learn more about how to make better prosthetics, and eventually help patients who have lost the use of a limb. Also, by learning more about how different sensory inputs can combine can have profound effects on new engineering approaches using robotics. The robot's sensory devices may take in inputs of different modalities, but if we understand multisensory integration better, we might be able to program these robots to convey these data into a useful output to better serve our purposes.


The word consciousness is used in a variety of ways that need to be distinguished. Sometimes the word means merely any human mental activity at all (as when one talks about the “history of consciousness”), and sometimes it means merely being awake (as in As the anesthetic wore off, the animal regained consciousness). The most philosophically troublesome usage concerns phenomena with which people seem to be “directly acquainted”—as the British philosopher Bertrand Russell (1872–1970) described them—each in his own case. Each person seems to have direct, immediate knowledge of his own conscious sensations and of the contents of his propositional attitudes—what he consciously thinks, believes, desires, hopes, fears, and so on. In common philosophical parlance, a person is said to have “ incorrigible” (or uncorrectable) access to his own mental states. For many people, the existence of these conscious states in their own case is more obvious and undeniable than anything else in the world. Indeed, the French mathematician and philosopher René Descartes (1596–1650) regarded his immediate conscious thoughts as the basis of all of the rest of his knowledge. Views that emphasize this first-person immediacy of conscious states have consequently come to be called “Cartesian.”

It turns out to be surprisingly difficult to say much about consciousness that is not highly controversial. Initial efforts in the 19th century to approach psychology with the rigour of other experimental sciences led researchers to engage in careful introspection of their own mental states. Although there emerged some interesting results regarding the relation of certain sensory states to external stimulation—for example, laws proposed by Gustav Theodor Fechner (1801–87) that relate the apparent to the real amplitude of a sound—much of the research dissolved into vagaries and complexities of experience that varied greatly over different individuals and about which interesting generalizations were not forthcoming.

It is worth pausing over some of the difficulties of introspection and the consequent pitfalls of thinking of conscious processes as the central subject matter of psychology. While it can seem natural to think that all mental phenomena are accessible to consciousness, close attention to the full range of cases suggests otherwise. The Austrian-born British philosopher Ludwig Wittgenstein (1889–1951) was particularly adept at calling attention to the rich and subtle variety of ordinary mental states and to how little they lend themselves to the model of an introspectively observed object. In a typical passage from his later writings (Zettel, §§484–504), he asked:

Is it hair-splitting to say: —joy, enjoyment, delight, are not sensations? —Let us at least ask ourselves: How much analogy is there between delight and what we call “sensation”? “I feel great joy” —Where? —that sounds like nonsense. And yet one does say “I feel a joyful agitation in my breast.” —But why is joy not localized? Is it because it is distributed over the whole body? … Love is not a feeling. Love is put to the test, pain not. One does not say: “That was not true pain, or it would not have gone off so quickly.”

In a related vein, the American linguist Ray Jackendoff proposed that one is never directly conscious of abstract ideas, such as goodness and justice—they are not items in the stream of consciousness. At best, one is aware of the perceptual qualities one might associate with such ideas—for example, an image of someone acting in a kindly way. While it can seem that there is something right in such suggestions, it also seems to be immensely difficult to determine exactly what the truth might be on the basis of introspection alone.

In the late 20th century, the validity and reliability of introspection were subject to much experimental study. In an influential review of the literature on “self-attribution,” the American psychologists Richard Nisbett and Timothy Wilson discussed a wide range of experiments that showed that people are often demonstrably mistaken about their own psychological processes. For example, in problem-solving tasks, people are often sensitive to crucial clues of which they are quite unaware, and they often provide patently confabulated accounts of the problem-solving methods they actually employ. Nisbett and Wilson speculated that in many cases introspection may not involve privileged access to one’s own mental states but rather the imposition upon oneself of popular theories about what mental states a person in one’s situation is likely to have. This possibility should be considered seriously when evaluating many of the traditional claims about the alleged incorrigibility of people’s access to their own minds.

In any event, it is important to note that not all mental phenomena are conscious. Indeed, the existence of unconscious mental states has been recognized in the West since the time of the ancient Greeks. Obvious examples include the beliefs, long-range plans, and desires that a person is not consciously thinking about at a particular time, as well as things that have “slipped one’s mind,” though they must in some way still be there, since one can be reminded of them. Plato thought that the kinds of a priori reasoning typically used in mathematics and geometry involve the “recollection” (anamnesis) of temporarily forgotten thoughts from a previous life. Modern followers of Sigmund Freud (1856–1939) have argued that a great many ordinary parapraxes (or “Freudian slips”) are the result of deeply repressed unconscious thoughts and desires. And, as noted above, many experiments reveal myriad ways in which people are unaware of, and sometimes demonstrably mistaken about, the character of their mental processes, which are therefore unconscious at least at the time they occur.

Partly out of frustration with introspectionism, psychologists during the first half of the 20th century tended to ignore consciousness entirely and instead study only “objective behaviour” (see below Radical behaviourism). In the last decades of the century, psychologists began to turn their attention once again to consciousness and introspection, but their methods differed radically from those of early introspectionists, in ways that can be understood against the background of other issues.

One might wonder what makes an unconscious mental process “mental” at all. If a person does not have immediate knowledge of it, why is it not merely part of the purely physical machinery of the brain? Why bring in mentality at all? Accessibility to consciousness, however, is not the only criterion for determining whether a given state or process is mental. One alternative criterion is that mental states and processes enter into the rationality of the systems of which they are a part.

Applications: Integrated Information Theory and Global Workspace Theory

This article proposes a map of consciousness studies, which consists of a systematic list of questions about consciousness and existing approaches to each question. In this final section, I apply this map to examine IIT and GWT. I first address how IIT answers each fundamental question that I have listed. In doing so, I point out several challenges to IIT. I then take the same procedure to examine GWT. I finally propose a way to clarify the relation between IIT and GWT with the help of the proposed map of consciousness studies. The discussion is sketchy but still sufficient to demonstrate how the proposed map can be used to examine and compare theories of consciousness.

Let us start with the definitional question. Tononi (2015, abstract, emphasis added) claims that IIT 𠇊ttempts to identify the essential properties of consciousness (axioms) and, from there, infers the properties of physical systems that can account for it (postulates).” He lists five essential properties of consciousness, namely, intrinsic existence, composition, information, integration, and exclusion, and calls them 𠇊xioms” (Tononi, 2015, sec. 2). The intrinsic existence axiom states that consciousness exists independently from external observers, the composition axiom states that consciousness is structured, the information axiom states that each conscious experience is the particular way it is and thereby it differs from other possible conscious experiences, the integration axiom states that consciousness is unified, and the exclusion axiom states that consciousness is definite in content and spatiotemporal grain 9 . The fact that they are called 𠇊xioms” suggests that the conjunction of the listed essential properties fixes the reference of 𠇌onsciousness.” Thus, IIT takes the essence-based approach to the definitional question, claiming that consciousness is defined in terms of the five axioms.

One slogan of IIT is that it goes 𠇏rom phenomenology to physics” (Tononi et al., 2016, p. 450) the axioms are called the “phenomenological axioms” (Oizumi et al., 2014). This indicates that the axioms are derived from phenomenological considerations, namely, by addressing the phenomenological question, in particular, the structure question of what invariant features consciousness has (since the essential properties of consciousness are the invariant of consciousness). This suggests that advocates of IIT answer the definitional question through tackling the structure question.

Advocates of IIT claim that the phenomenological axioms �nnot be doubted and do not need proof” and are “taken to be immediately evident” (Oizumi et al., 2014, p. 2). This shows that they take the introspection approach to the structure question, rather than the observation approach and the reasoning approach, to derive the phenomenological axioms. However, some philosophers cast doubt on the plausibility of the axioms as capturing the essential phenomenological features of consciousness (Bayne, 2018 Pokropski, 2018 Miyahara and Witkowski, 2019). This demonstrates that the phenomenological axioms can be doubted and should not be taken to be immediately evident. Thus, advocates of IIT must justify the phenomenological axioms, employing the other approaches if needed.

Let us next move onto the ontological question. IIT specifies five informational features of physical systems (so-called “postulates”), each of which is supposed to account for a corresponding phenomenological axiom, and states that every physical system that realizes the five postulates possesses consciousness 10 . This statement is counted as the answer to the distribution question. Nevertheless, it is not fully clear what reasoning is in play here (especially in what sense each postulate �ounts for” a corresponding phenomenological axiom and why each postulate necessitates the phenomenological feature represented by the corresponding axiom). In order to evaluate IIT’s answer to the distribution question, thus, we should clarify the exact premises and inferential steps that constitute the reasoning in question.

IIT answers the mind𠄻ody question by stating that conscious experience is identical to an integrated informational structure of physical systems that instantiates the five postulates (Tononi, 2015, sec. 4). There is, however, no mention of how the identity claim is derived in any IIT literature. As we have seen in section 𠇊pproaches to the Ontological Question”, identity is not reasonably inferred only from the presence of correlation, since other metaphysical relations such as causal relation and grounding relation are also compatible with the presence of correlation. To justify the identity claim, advocates of IIT need to clarify what theses they use as the premises for the reasoning in question, in addition to the experimental finding that there is a correlation between the presence of consciousness and a relevant informational structure of brains (Massimini et al., 2005). Otherwise, we cannot properly evaluate IIT’s identity claim.

Let us finally examine what implications IIT have for the epistemological and the axiological questions. First, IIT seems to have an implication for the epistemological question about the consciousness of others. IIT states that the phenomenological features of consciousness (in particular contents and dimensions) are reflected in the form of the informational structure of physical systems (Tononi, 2015, sec. 4 Tononi et al., 2016, p. 459). It follows from this that we can infer the phenomenological features of the consciousness of others from the form of the informational structure of their brain, which we can, in principle, specify from the third-person perspective. This can be counted as an answer to the epistemological question about the consciousness of others. IIT also has an implication for the cognitive value question. If it is cognitively advantageous for physical systems to generate information in an integrated manner, IIT implies that the possession of consciousness is cognitively advantageous for that very reason.

I turn to how GWT (in particular its major advocate Stanislas Dehaene) answers each fundamental question listed in The List of Questions section. Dehaene (2014, pp. 8, 9) defines consciousness in terms of 𠇌onscious access”: the content of mental state/process is consciously accessible if and only if it enters awareness and becomes reportable to others. This definition consists of two notions, awareness and reportability. The property of being reportable serves to provide an informative definition of consciousness, since we can set out an objective procedure to determine whether a piece of information is reportable for its possessor. In contrast, it is unclear how 𠇊wareness” is different from 𠇌onsciousness” in our ordinary conceptual understandings. Furthermore, it is unclear what behavioral standard can be used to determine whether one is aware of a piece of information, as being different from the one for reportability. Nevertheless, Dehaene does not seem to provide an analytic explanation of the notion of awareness. Instead, he presents a few examples of being aware of something. For instance, he presents an example of visual illusion and states:

Twelve dots, printed in light gray, surround a black cross. Now stare intently at the central cross. After a few seconds, you should see some of the gray dots fade in and out of existence. For a few seconds, they vanish from your awareness then they pop back in. Sometimes the entire set goes away, temporarily leaving you with a blank page—only to return a few seconds later with a seemingly darker shade of gray. (Dehaene, 2014, p. 17)

This suggests that Dehaene leads his readers to grasp the sense of 𠇊wareness” through the examples presented in his book. If this is correct, his definition of consciousness is not entirely operational, for it does not reduce the sense of 𠇌onsciousness” to reportability alone. In defining consciousness, Dehaene seems to take the example-based and essence-based approaches in combination the former corresponds to the 𠇊wareness” part, and the latter corresponds to the “reportability” part.

Dehaene (2014, chap. 4) takes the correlation approach to the mind𠄻ody question, presenting many relevant empirical findings 11 . Based on them, he identifies four physiological markers that index whether a stimulus is consciously accessible:

First, a conscious stimulus causes an intense neuronal activation that leads to a sudden ignition of parietal and prefrontal circuits. Second, in the EEG, conscious access is accompanied by a slow wave called the P3 wave, which emerges as late as one-third of a second after the stimulus. Third, conscious ignition also triggers a late and sudden burst of high-frequency oscillations. Finally, many regions exchange bidirectional and synchronized messages over long distances in the cortex, thus forming a global brain web. (Dehaene, 2014, pp. 158, 159)

Dehaene then provides a functionalist account as to why consciousness is correlated with those physiological makers.

The human brain has developed efficient long-distance networks, particularly in the prefrontal cortex, to select relevant information and disseminate it throughout the brain. Consciousness is an evolved device that allows us to attend to a piece of information and keep it active within this broadcasting system. Once the information is conscious, it can be flexibly routed to other areas according to our current goals. Thus we can name it, evaluate it, memorize it, or use it to plan the future (Dehaene, 2014, p. 161).

This functionalist account describes how a piece of information is cognitively processed in our brain when it is consciously accessible and thereby explains why the above physiological makers occur in functional terms. This account is thus an empirically supported correlation-based answer to the mind𠄻ody question. This is, I think, the core thesis of GWT. However, Dehaene (2014, p. 161) goes beyond the empirically supported claim regarding correlation, claiming that 𠇌onsciousness is brain-wide information sharing.” If we interpreted this statement literally, it would mean the identity between consciousness and the brain-wide information sharing. However, this identity claim does not directly follow from the empirically supported claim about correlation. If Dehaene (2014) defined consciousness only in terms of reportability, then the identity claim would be derived from the fact that reportability can be reductively explained in terms of brain-wide information sharing. However, Dehaene (2014) includes 𠇊wareness” in his definition of consciousness, which is supposed to be grasped through examples. It is unclear whether the property of being aware of something is considered to be reductively explained in functional terms, unlike reportability. Thus, Dehaene is required to explain why the property of being aware of something should be counted as standing in the identity relation, rather than other metaphysical relations, to the brain-wide information sharing. As in the case of IIT, we cannot properly evaluate IIT’s identity claim unless some explanation is provided.

Global workspace theory has implications for (i) the cognitive value question, (ii) the epistemological question about the consciousness of others, and (iii) the distribution question. Given that a piece of information can be flexibly routed to many brain areas only when it is consciously accessible, it is plausible to think that (i) consciousness enables its possessor to process information in such flexible manners (Dehaene, 2014, chap. 3) and that (ii) we can know about the content of the consciousness of others by detecting the information widely shared in his/her brain. (iii) It follows from GWT’s identity claim that every creature who has 𠇋rain-wide information sharing” is conscious (Dehaene, 2014, chap. 6.7).

We can clarify the relation between IIT and GWT by comparing their answers to each fundamental question. Let us take three questions, for example, the definitional question, the mind𠄻ody question, and the distribution question. For the definitional question, IIT states that consciousness is defined in terms of the five phenomenological axioms, which are supposed to capture the essential properties of consciousness. In contrast, GWT defines consciousness in terms of awareness and reportability. By comparing the two definitions of consciousness, we can examine whether IIT and GWT have the same research subject in the first place. For the mind𠄻ody question, IIT states that conscious experience is identical to an integrated informational structure of physical systems that instantiates the five postulates. In contrast, GWT states that consciousness is brain-wide information sharing. By comparing the two identity claims, we can examine whether they are compatible or conflicting. For the distribution question, IIT states that every physical system that realizes the five postulates possesses consciousness. In contrast, GWT implies that every creature who has brain-wide information sharing has consciousness. By examining whether each kind of creature overlaps, we can see whether IIT and GWT substantially differ in what existing creatures/entities have consciousness. In this way, we can conduct a multidimensional comparison between IIT and GWT. This enables us to assess the two theories systematically and comparatively in the multidimensional evaluative space.

I close this article by presenting three ideas on how to proceed with consciousness research with the help of the lists of questions and approaches proposed in this article. First, we should examine how existing theories of consciousness answer each fundamental question about consciousness and what approach their advocates adopt. By doing so, we can obtain systematic understandings of each theory of consciousness, which enable us to see what part of each theory of consciousness needs to be justified and developed. Second, we should conduct a multidimensional comparison of the existing theories of consciousness. This enables us to obtain a detailed and well-organized review of how they are related to each other. These two points have been demonstrated in the discussions of IIT and GWT. Third, each research group should clarify what question and approach to take in investigating consciousness. By doing so, they can be aware of the scope, limitation, and potential implications of their research project and also of its relations to existing theories of consciousness.

Although I believe that the proposed lists of questions and approaches contribute to the development of consciousness studies, I do not think that they are entirely satisfactory. The map of consciousness studies presented in this article can be revised and further enriched. I hope that this article also works as a springboard for a further second-order investigation on consciousness studies as being distinct from the first-order investigation on consciousness.