Descartes’ Error: Emotion, Reason and the Human Brain

In 1637, when Descartes first proclaimed what would later be known as one of the most foundational philosophical statements in history, “I think therefore I am,” he did not have available the tools and understandings of modern neuroscience we have today. In his book, Descartes’ Error, Antonio Damasio challenges the idea of mind-body dualism that has so pervaded culture since Descartes’ assertion, by approaching the question from the opposite direction.  Beginning with what neuroscience and evolution tell us about “being,” Damasio works his way through the concepts of imagery, memory, intuition, emotion and reason to finally arrive at thinking. Damasio offers an explanation for mental imagery and reasoning – concepts often perceived to exist outside of the physical realm of the body – that roots them firmly and inextricably as parts of the workings of the body. Not only does he show that the concept of “pure reason” – one of the central goals of philosophical inquest throughout all of history – is an illusory concept, but continues on to make emotion and the physical body the basis for the mere possibility of reason.

Though Damasio offers clinical cases and examples to support all of his claims, the overall tone of the book is one more philosophical and abstract than scientific. Nonetheless, Damasio prefaces his abstract exploration into the mind with specific cases of neurological damage to the ventromedial prefrontal cortices, and right hemisphere somatosensory cortices, which he postulates play a large role in emotional and rational thought. Additionally, he cites clinical studies testing the ways in which such damage impairs human emotional and rational capabilities. He concludes that it impairs a person’s ability to assign emotional significance to events happening in the present, which results in impaired decision making and reasoning. In the realm of reasoning and consciousness, any story that takes behavioral studies and brain damage and jumps to an explanation in terms of concepts such as mental imagery and reasoning involves some philosophical theorizing; however, in general Damasio’s evidence is well explained and presented without bias, and he clearly differentiates between when he is presenting clinically tested hypotheses, and when he is entering into the realm of the theoretical.

What I found to be perhaps the most revolutionary of Damasio’s ideas was his neurobiological explanation for mental imagery and memory.  He sets out to disprove the common conception “that what is together in the mind is together at one place in the brain where different sensory aspects mingle.” (94) When we conjure up an image in our mind, we are putting together all sorts of remembered sensory information about that image – shapes, colors, smells, feels – and because these all come together in one image in our mind, we assume they must all be stored together in the brain. What Damasio counters with however, is that “there is no single region in the human brain equipped to process, simultaneously, representations from all the sensory modalities active when we experience simultaneously, say, sound, movement, shape and color in perfect temporal and spatial registration.” (94-5) What causes us to perceive all of these factors as linked to one object is in fact only their simultaneity in time, not their interconnectivity in the brain. Damasio calls the integration of different sensory information into one concept a “trick of timing” (95). With obvious Kantian undertones, Damasio places time (and space, in terms of where on the body a stimulus acts) as the ultimate concepts that create our understanding of “absolute reality.” A mental image is nothing more than a specific pattern of simultaneously firing sensory neurons. Additionally, Damasio asserts that there is no difference in the mechanism of creation between the image we have in our mind of something as we actively perceive it (the first time that pattern of nerve firings has occurred), and the image we create in our mind when we remember something.  

Yet if this is the case, we must have some neural machinery that allows us to store patterns of neural activity. In the place of one, unified neural region storing sensory information, Damasio offer up a method by which the patterns of simultaneously occurring neural firings that constitute an image can be stored in the brain as what he calls “dispositional representations”. These are essentially maps of neural firing commands that when activated reproduce the same patterns of neuron firings that initially created an image during perception.

Damasio explains that through studying neural firing, it is known that image perception initially occurs as patterns of activity in the early sensory cortices. When a dispositional representation is activated, is sends a message to the early sensory cortices (and perhaps to other dispositional representations) involved in creating the image, telling them to fire and thus recreate the image. The image will most likely not be exactly the same as the original perception, but will retain many of the same elements. Damasio briefly theorizes that he believes the neurobiological explanation for dispositional representations is the strengthening or weakening of synapses.

Calling to mind an image, or in other words, memory, is thus an inherently reconstructive process. This central difference between Damasio’s explanation of memory, and the view of images as being stored as unified concept in the mind, is the base of his entire philosophy. Our images are not made by perceptions and then removed from the body to be replayed only in the mind as a kind of movie – they are instead saved as patterns of firing that recreate the image in the mind only by reconstructing the physical, bodily experience of the perception of the image in the early sensory cortices. Damasio explains how there can be some variation in the extent to which the body must recreate the experience of the image in order to create the effect in the mind, but in general it is this concept – that body, brain and mind are all necessarily involved in thought and memory equally – that underlies Damasio’s philosophy and sets it apart from those in favor or dualism and “pure reason.”

Images, both perceptual and mental, have their own effects on the body above and beyond the firing patterns they produce in the early sensory cortices, and it is these effects that Damasio calls emotions. Emotions, as separate from feelings, are the physical manifestations of thoughts and imagery. For example, increased pulse and sweat production when one perceives something scary are examples of an emotional response.  Emotions can be primary -preprogrammed physical dispositions to stimuli as a result of evolution - or they can be secondary dispositions that are acquired as we associate certain types of situations with certain emotional responses over time. The feeling of an emotion is, as Damasio explains the “process of continuous monitoring, that experience of what your body is doing while thoughts about specific contents roll by” (145). In other words, a feeling is a change in the emotional state of the body, juxtaposed with either the mental or perceptual image that simultaneously occurred in the mind. It is this element of emotion that we become aware of in our conscious. We feel change.

As we continue through life we continuously form more and more dispositional representations that link certain feelings and emotions. Dispositional representations occur below the level of consciousness, meaning we can arrive at feeling a certain way without being aware of exactly how we got there. If an image contained an element we had a disposition to feel badly about, we would mostly likely generate a negative feeling about the whole image by association. Damasio has a special name for this theory, which he calls the “somatic-marker hypothesis.” As he explains: “somatic markers are a special instance of feelings generated from secondary emotions. Those emotions and feelings have been connected, by learning, to predicted future outcomes of certain scenarios.” (174)

What this hypothesis means, if true, is that every decision we come to, every intuitive feeling we have, has already had our own personal bias attached to it. In Mental Health and the Brain we discussed how at a basic level, all of our sensory information comes to us through the lens of our own interpretation. The blue that you see may not be the blue that I see. What Damasio is here suggesting, however, is that even ideas we believe we have arrived at logically, ideas much more complex than basic sensory perception, are in fact products of unconscious interpretation we have learned over time and developed dispositional representations for.  “Pure reason” that is free from emotion or personal bias is an illusion. Every image we conjure up in our mind has attached to it some emotional response and its associated feeling.

Does this mean that no form of rational decision making exits? Of course not. The extent of emotional response to an image can have a huge range, from vastly overpowering to essentially negligible. Additionally, that somatic markers perform some interpretive steps before allowing you to become conscious of an image is not a bad thing – in fact, it is what makes rational decision making possible at all. As Damasio explains, if we were to have no somatic markers, we would have to re-analyze every single dimension and element of every scenario before making decisions. But this task is impossible! Not only do we not have enough active memory to hold in our mind all the factors involved, but we can’t possibly have the time to perform such logical analyses for everything we do. Somatic markers allow us to build in automatic responses to certain more common stimuli, such that we can focus on logical deliberation between factors that are perhaps more unique or important. Additionally, this logical deliberation can involve conscious re-interpretation of events in the hopes of forming new dispositional representations. We have discussed at great length in Mental Health in the Brain how conscious thought done by the storyteller can affect the unconscious, and I think this is a prime example. We may have arrived at a certain initial emotional response because of somatic markers, but once there, our conscious thought about that scenario will inevitably be encompassed in the editing of that dispositional representation for future use.

Another important element of somatic markers is that they can sometimes produce feelings and emotions in response to unconscious stimuli. Since we are not consciously aware of our dispositional representations, and since these representations can signal other dispositional representations as well as the early sensory cortices, sometimes images can end up producing feelings in us we have never been consciously aware could be connected before. If we are imagining something happy while at the same time feeling sad, such a conflict could prove very distressing if the somatic markers responsible cannot be identified. This in large part relates to much of what we have been talking about in Mental Health and the Brain – that conflict between the unconscious and the conscious results in mental health distress – and I think Damasio’s somatic-marker hypothesis offers an excellent explanation for this conflict.    

One last element of Descartes’ Error that I shall only touch on briefly is Damasio’s discussion of how the role of the “self” might be explained neurobiologically. Essentially, he theorizes that the self is a set of dispositional representations that continuously fires all the time. Thus, as the change in emotional states is assessed in the generation of feelings, change is always set against the backdrop of a continuously present set of stimuli that constitute the self. Damasio much further explores this idea in his next book, The Feeling of what Happens: Body and Emotion in the Making of Consciousness, but it is evident the seeds for his exploration of consciousness and the self can be found in his theories about feeling and emotion.

A recurring theme throughout Damasio’s book, and perhaps a good note to end on, is that Damasio feels strongly that explaining concepts such as intuition and feeling using neurobiological constructs should not rob them of their meaning. He feels that instead knowing how deeply rooted feeling is in biology, that even more than an abstract concept, feeling is actually a psychological reality, should give even more meaning to our feelings than if they were only concepts in the mind. I myself struggle to fully accept that this explanation does not rob meaning of some element that made it special, but I am also comforted in some ways by the fact that it shows that what we find meaningful is in some ways “predestined” by evolution. Our primary emotions are innate responses, and since it is primary emotions that shape secondary ones and thus somatic markers, in a sense we are predestined to feel certain ways about certain things. Meaning is still an entirely personal construct, and does not exist as “absolute reality”, but in the sense that it is rooted in the unconscious, it could indeed be a personal absolute reality.  

Sources

Damasio, Antonio. Descartes' Error. New York. Penguin Books, 1994.

Damasio, Antonio. The Feeling of What Happens. New York: Harcourt Brace, 1999.