How Neuroscience Explains Consciousness

Consciousness can be explained as the integration of several functions of the brain

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Question 1 - How does the brain produce consciousness?

I would define consciousness as the property of our mind by which we are aware of our surroundings, body sensations, and what we are doing. It also tells us that we exist as minds that have thoughts, memories and emotions.


In the scientific worldview, everything that happens in our mind is the product of the activity of the brain. However, some philosophers like David Chalmers sustain that there is something mysterious and ineffable about consciousness, which science will never be able to explain as brain activity. Is this a leftover from a belief in the soul and other religious ideas? Or is there something special about consciousness that is forever beyond the reach of science?


Question 2 - Are animals conscious? If so, are there differences between human and animal consciousness?

When we look at our cat or our dog, we get the feeling that they are aware of the world the same way as we are. However, most people would have trouble believing that simple animals like clams, corals, barnacles, snails or flies are conscious. If you chose to believe that these animals are conscious, then you would have a hard time explaining why plants are not conscious. And if you chose to believe that plants are conscious, too, then you are well on your way to panpsychism: the belief that everything is conscious. Then you will face an even harder problem: explaining how our consciousness and the consciousness of a rock are different.


On the other hand, if some animals are conscious and others are not, then something must have happened during evolution that gave rise to consciousness. Which leads to the next question…


Question 3 - How did consciousness emerge during evolution?

Some people argue that consciousness has no adaptive value, that it is superfluous for natural selection. They think that consciousness is an epiphenomenon: something secondary that occurs alongside mental processes. According to that view, the appearance of conscious beings like us is just a fluke of evolution. Is that true?


Sensory consciousness

In order for us to function in the world, our brain must integrate different sensory modalities into one unified model of the word. When we look at a girl playing guitar, we intuitively know that the sound we hear comes from the guitar we see, and that the movement of her fingers produces the sound. Vision and hearing are spatial senses that assign a particular place to a particular perception. The mind places what we see and what we hear in the same common perceptual space. Touch is also spatial, and it is also integrated with vision and sound into that perceptual space.


Interoception is the sensations that we receive from inside of the body. They tell us the position of our limbs, the level of contraction and relaxation of our muscles, the state of our viscera, whether something hurts, etc. It is comprised of several senses: balance, visceral feelings, cold, heat, pain and itch. Since we know in what place of our body we feel a certain sensation, interoception is also spatial. And since we must move our body in the world that we perceive through our external senses, interoception has to be integrated into the same model of the world generated by the external senses, vision and hearing.


All our perceptions (except smell) converge in the thalamus, a region at the core of the brain. The thalamus sends nerves to the primary sensory areas of the cortex, such as the visual cortex in the back of the brain or the somatosensory cortex just behind the central sulcus. These primary sensory areas send the information to other areas of the brain, where they get progressively integrated and placed in the perceptual space.


Importantly, the brain also attributes a certain importance - or “valence” - to a perception, by assigning an emotion to it. Thus, perceptions may be classified as scary, angering, sexually arousing, interesting, etc. Sensations that lack emotional valence are eliminated from awareness, while those with high emotional content are given a central place in the mind. This makes sense because it is critical for our survival that perceptions are set in a hierarchy according to the danger they represent and their relevance for the task that we are trying to accomplish.


Creating this model of the world that unifies all our perceptions is the basis of our awareness. But this is just a first layer of consciousness. We share this ability with other animals with a complex nervous system.


There is an evolutionary advantage in constructing a unified model of the world. Otherwise, the animal would not be able to make sense of the world and act inside it.


Which takes us to the next building block of consciousness.


Motor consciousness

As I explained in another article, agency is a property of all living beings by which they are able to generate internal causes. In simple terms, living beings do stuff. Plants do stuff by growing. Animals do stuff by moving because, unlike plants, they have muscles. In addition, complex animals have a nervous system that allows them to gather information from the world and plan their movements.


Animals do not just perceive the world, they move and do things. They search for drink, food and mates. They escape predators. They care for their offspring. They do that by planning movements using the same model of the world created by the perceptual aspects of consciousness.


The central sulcus is a deep gash in the brain that, together with the lateral fissure, divides the cortex into a frontal and a posterior part. Roughly speaking, the posterior part of the cortex is in charge of processing sensory information and the anterior part is in charge of planning action. In humans, the anterior cingulate cortex and the prefrontal cortex are in charge of motivation and making decisions about what to do next. From there, movement is planned by the motor cortex, just anterior of the central sulcus, and finessed at the cerebellum. Then motor commands are sent to the muscles, down the spinal cord and through the motor nerves.


However, there is another kind of motor function that has great importance in humans: that of the mind searching and manipulating its own contents. It may be looking for a specific memory, imagining something or dealing with abstract concepts.


While animals focus on the outside, we spend a considerable part of our lives inside our heads.


The creation of the self

The self appears when our body becomes an object in the perceptual space created by the brain to integrate the sensations from different senses. The body has to be in that perceptual space all the time because everything we perceive is from the body. Moreover, when we plan or execute a movement, what moves is the body. Movement will become uncoordinated without a careful feedback between movement and perception.


Because of the critical importance of that coordination, the body is not just another object in the perceptual space: it is at the interface between the perception of what is outside (exteroception: vision, hearing, touch, etc.) and what is inside (interoception). Therefore, awareness of the body takes a central role: it becomes the self [1,3].


This is a primordial self that humans share with other animals with a complex nervous system. It is a “protoself”, as neuroscientist Antonio Damasio calls it.


Extended Consciousness

Extended Consciousness is a concept developed by Antonio Damasio in his book The Feeling of What Happens [5], which proposes a hierarchical theory of consciousness. Everything I have described so far is what Damasio calls “Core Consciousness”. Here is how he describes Extended Consciousness:


“Extended consciousness goes beyond the here and now of core consciousness, both back and forward. The here and now is still there, but it is flanked by the past, as much past as you may need to illuminate the now effectively, and, just as importantly, it is flanked by the anticipated future.” Antonio Damasio, The Feeling of What Happens [5].


Just like core consciousness gives rise to the protoself, extended consciousness gives rise to the “autobiographical self”:


“The autobiographical self relies on the consistent reactivation and display of selected sets of autobiographical memories.” Antonio Damasio, The Feeling of What Happens [5].


Shame, pride and the construction of the ego

I propose that what we call the ego - or the super-ego in Sigmund Freud’s psychoanalysis - arises when the autobiographical self is colored by two important human emotions: shame and pride. These emotions evolved when human survival became dependent on our ability to cooperate with each other. They indicate changes in our social status. If we fail to cooperate or we act selfishly, we are shamed and our social status decreases. If, on the other hand, we do something beneficial to the group, we are praised and our social status increases.


Shame and pride change our self-esteem, which is essential for our internal well-being. As our autobiography gets highlighted by instances of shame and pride, we build an image of who we are and how we expect ourselves to behave. That is our ego.


I think that the ego is an important part of the autobiographical self but not identical to it, because we can construct images of ourselves that are free of judgment and thus independent of shame and pride.


Self-directed theory-of-mind

Theory-of-mind (not to be confused with a theory of the mind) is a unique faculty of humans that allows us to model the minds of other people [11]. We refer to it when we say “I know what you are thinking”. Not only it models what other people know, but also their emotions. When we talk about “walking in her shoes”, we are referring to using our theory-of-mind to imagine the feelings of another person.


Theory-of-mind is far from infallible and may generate problems. It works reasonably well when applied to people with minds similar to our own, less well when applied to people of different cultures, and quite badly when we apply it to animals to assume that they think like us (anthropomorphism). It is also at the core of many superstitions - when it leads us to believe that inanimate objects and natural phenomena have minds and can be treated as human beings.


According to neuroscientist Bud Craig (an expert in pain and interoception), the radical changes from core consciousness in animals to extended consciousness in humans are due to the development of a specialized part of the cortex called the anterior insula, during the evolution of primates [2,4,7]. The right anterior insula has the function of creating hypothetical perceptions of the internal state of the body (proprioception). If I imagine what it would feel like to have a headache, it is my right anterior insula doing the work. Because of its ability to imagine feelings, the right anterior insula may play an essential role in theory-of-mind.


Craig also proposes that the neuronal links between the anterior insula and the anterior cingulate cortex - an area of the brain that mediates decision and action planning [9] - play a key role in consciousness. Indeed, the capacity of the anterior insula to imagine feelings may serve to provide emotional depth to our autobiographical memories and to what we imagine may happen to us in the future.


The anterior insula also mediates empathy because it allows us to imagine what others are feeling [8].


As I said at the beginning, an important aspect of consciousness is that it lets us know that we exist as minds that are able to have thoughts, memories and emotions. This awareness of having a mind may be the result of applying theory-of-mind to our own mind.


Neuroscientists Michael S. Gazzaniga (who studied split-brain patients) and Joseph E. LeDoux (an authority in emotions) propose that there is a module in the human mind that they call “the interpreter”, whose function is to construct a continuous narrative of what is happening in our minds. This may be theory-of-mind applied to ourselves. Unfortunately, the interpreter is often wrong. Maybe its accuracy can be improved by training ourselves to observe our minds more objectively with techniques like mindfulness.


Cultural consciousness

Constructing our autobiographical self, our ego, and the ongoing interpretation of our own mental activity are cognitive functions. As such, they are highly dependent on our beliefs and our values. And those values are framed by the culture in which we live.


Therefore, it is true that our culture influences our consciousness. However, by the same token, it is also true that the more educated and mindful we become, the more our consciousness becomes free of illusion and negative feelings.


Far from being determined by our genes or our environment, human consciousness is malleable and trainable. There is plenty of evidence that we can influence the most basic mechanisms of our consciousness by taking drugs or with practices like yoga, mindfulness or meditation. With the right knowledge and hard work, we can truly change our minds.


Answer to question 1: How does the brain produce consciousness?

Everything the brain does contributes to consciousness. We experience life as a series of mind frames - like the pictures in a movie - which are made of perceptions, emotions, ideas, and self-awareness that come from very different places in the brain.


The way we divide our minds between the conscious and the unconscious is largely illusory. There are only perceptions that are important enough to be noted and remembered and those that are pushed away because they will just clutter our mind [6].


Consciousness is not mysterious, ineffable, or unitary. It does not exist independently from the contents of the mind.


Answer to question 2: Are animals conscious? If so, are there differences between human and animal consciousness?

Animals with complex nervous systems, like mammals and birds, have core consciousness.

Most other animal species (insects, clams, snails, worms, corals, jellies, sea urchins, sponges, etc.) are unconscious automatons because they lack nervous systems complex enough to produce a sophisticated representation of their bodies in their environment. They have only a series of pre-determined behaviors in response to specific stimuli, like the computers that run self-driving cars.


Other animals (fish, lizards, octopi) are somewhere in between. The boundary between what animals are conscious and what animals are not, is fuzzy.


However, only humans have extended consciousness, an ego, theory-of-mind, an interpreter, and cultural consciousness. Of course, since evolution is a continuum, as we move closer to humans we see some of these properties gradually emerging. For example, a rudimentary theory-of-mind has been detected in chimps [10].


Surprisingly, some primordial extended consciousness seems to be present in animals that are not in the direct evolutionary lineage of humans, like dolphins, elephants, parrots and crows. This suggests that extended consciousness is not an evolutionary fluke but an important adaptation that will come up over and over again in the roulette of mutation and natural selection.


Answer to question 3: How did consciousness emerge during evolution?

Consciousness is not an epiphenomenon but the logical result of the need to integrate perception and movement into a common model. The same need for integration of perception and action arises when we design a robot or a self-driving car. Furthermore, a representation of the body as a key object that needs to be protected gives rise spontaneously to the protoself.


The evolutionary advantage of effective cooperation, and the need to share and store large amounts of information, are sufficient to explain the emergence of extended consciousness in humans. In a way, it is an indirect consequence of other adaptive properties of the mind such as social emotions, autobiographical memory and theory-of-mind. These properties are so closely linked to extended consciousness as to make it inevitable.


Consciousness is a natural phenomenon. It is time that we leave behind mystical ideas that it is some mysterious essence that exists separate from matter. Consciousness, like life, becomes even more beautiful and awesome as we understand its amazing complexity.


References

  1. Craig, A D. Human feelings: why are some more aware than others? Trends Cogn Sci 8: 239-241 (2004)

  2. Craig, A D. How do you feel--now? The anterior insula and human awareness. Nat Rev Neurosci 10: 59-70 (2009)

  3. Craig, A D. The sentient self. Brain Struct Funct 214: 563-577 (2010)

  4. Craig, A D. Significance of the insula for the evolution of human awareness of feelings from the body. Ann N Y Acad Sci 1225: 72-82 (2011)

  5. Damasio, A R, The Feeling of What Happens: Body and Emotion in the Making of Consciousness. 1999, San Diego, New York, London: Harcourt, Inc.

  6. Dennett, D C, Consciousness Explained. First ed. 1991, Boston, Toronto, London: Little, Brown and Co.

  7. Gogolla, N. The insular cortex. Curr Biol 27: R580-R586 (2017)

  8. Gu, X, X Liu, K G Guise, T P Naidich, P R Hof, J Fan. Functional Dissociation of the Frontoinsular and Anterior Cingulate Cortices in Empathy for Pain. J Neurosci 30: 3739-3744 (2010)

  9. Isomura, Y, Y Ito, T Akazawa, A Nambu, M Takada. Neural Coding of "Attention for Action" and "Response Selection" in Primate Anterior Cingulate Cortex. J Neurosci 23: 8002-8012 (2003)

  10. Krupenye, C, F Kano, S Hirata, J Call, M Tomasello. Great apes anticipate that other individuals will act according to false beliefs. Science 354: 110-114 (2016)

  11. Penn, D C, D J Povinelli. On the lack of evidence that non-human animals possess anything remotely resembling a 'theory of mind'. Philosophical transactions of the Royal Society of London Series B, Biological sciences 362: 731-744 (2007)

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