IS CONSCIOUSNESS SPIRIT, OR SIMPLY SEQUENCE? DANIEL PURSUES NEURAL PATHWAYS OF HUMAN AGENCY.

Consciousness can be investigated from the perspectives of philosophy and neuroscience. Common aspects of this debate include agency, subjectivity and continuity of experience, and selective awareness of information. From a neuroscience perspective, the nature and existence of consciousness are controversial and under-researched areas of brain functionality.



As a student of neuroscience, I find consciousness difficult to discuss because of a basic logic problem: Talking about consciousness blurs the apparent boundary between subject and object. It is exceptionally challenging to separate the topic being discussed from the sentient entity (or entities) involved in the discussion. The object that the subject investigates is what defines the subject as a subject, as opposed to an object. Is it even possible, then, for a subject to objectively define or describe his or her own subjecthood? Philosophy of mind discussions often break down into a circular war of semantics.

Historically, thinking on the consciousness has been divided into two camps: monism and dualism. Monism posits that, as scientists, we cannot support the presence of any entities or agents that are neither comprised of matter, nor subject to the laws of physics. The mind—though it may seem somehow qualitatively different from the physical entity of the body—must nonetheless be composed of the same evidential physical or physiological features as the body. If the brain is the information-processing center of the body, then the conscious mind, if it can be said to exist, must either emerge as a property of the brain, or be identical to it. The mind cannot have a separate existence.



Dualism, however, has been the king of the consciousness debate for most of Western intellectual history. The dualist camp posits that, either explicitly or implicitly, the mind is somehow distinct from the brain. Until very recently, thinkers were more comfortable characterizing consciousness as supernatural or spiritual in some way. Plato posited a kind of dualism in describing the world of Forms, literally separating reality into one realm of base perception, and one of Truth. True consciousness emerged when the mind's perception abutted this latter world. Plato extended this metaphor to suggest that the mind—i.e., that part of us in contact with Truth-forms—is a prisoner trapped in the body, full as it is of deceptive animal impulses. In so doing, Plato established a separation from what we encounter or perceive as physical beings, versus some separate aspect of cognition that more holistically defines us as something more than "mere flesh."

The notion that our "soul" or "mind" is the part of us that is truly us - and not merely a function of our biology or environment- is found in an expanse of writings and testimonies, ranging from Pre-Socratics like Pythagoras, to the great texts of nearly all of the world's major religions. With a few blips along the way, the idea that we are divided between mind/soul and body has been endemic to linguistic and social programming for most of human history. I think this is because consciousness presents us with some powerful illusions: The conscious mind feels like the driver of our behavior. It seems clear to us that the same mental process that produces our inner monologue is responsible for producing our external behavior, save for involuntary or reflex-level responses. The introspective, and apparently considered character of our complex behaviors strikes us as instinctively separate from the otherwise "dumb" functioning of our brain, the organ.

Modern dualism derives from philosopher René Descartes, who on the basis of physiological evidence concluded that the brain as a physical entity is crucial to regulating behavior and emotion—but that there must also exist some separate "seat of reason" with non-corporeal properties. This view is described throughout his writings, but most cohesively fleshed out in The Passions of the Soul. In Descartes' reasoning, since the soul/mind can be used to examine itself, it appears to be wholly different from other physiological phenomena. That is to say, the soul/mind can operate without having externally apparent physical effects. It must therefore be comprised of different material, and have different properties than the body since its operation leaves no physiological trace.

Descartes declared that the point of contact between the corporeal body and the non-corporeal mind was the pineal gland, a small structure near the ventricles of the brain. The sensory organs record a perception that is then transmitted to the mind by way of this gland. More recent research has indicated that the pineal gland is responsible for the secretion of melatonin, a hormone that is pivotal in the regulation of the sleep-wake cycle. It clearly plays no significant role in the production of consciousness.



Indeed, no single brain structure has been identified as being central to our personality or "humanness." Moreover, thoughts do indeed leave physiological markers, as seen in EEGs and fMRIs. In spite of the total lack of supporting biological evidence for any structure in the brain that operates independently from the rest of it, the notion of a "seat of reason" persists. Since there is no evidence to indicate any physical location for mind as such, dualism necessarily invokes a kind of supernaturalism, which should make it anathema to scientists.

But the first advocate of monism approached the question of consciousness from a religious perspective. Baruch de Spinoza was a philosopher whose explicit rejection of dualism still directs philosophy of mind conversations in the sciences today. In his 1677 work, The Ethics, Spinoza argues that the universe is constructed of a single, physical "substance" which is subject to universal rules of causation. He further posited that, given God's nature as the ultimate cause, all things must be constructed by and from God. Spinoza concluded that the brain and mind are of a single, common material and as such, cannot be separated, as both are constructed of God's substance.  

We know through lesion studies that physically altering the brain along many different points can produce profound alterations or disruptions of consciousness. Lesion studies, executed using the research techniques of double dissociation, are a gold standard in neuropsychology (as well as neuroscience in general). Where imaging studies can show us only correlations between mental events and brain metabolic activity, lesions can pinpoint areas crucial to the way the mind/brain receives or integrates information and produces behavior.



Lesions of the corpus collusum, a band of tissues which connects the two cerebral hemispheres, can tell us some very interesting things about the way consciousness operates, and its connection to a diffuse array of physical structures. When the corpus collusum is severed, a condition known as "split brain" is produced. Split-brain subjects appear clinically normal before this procedure but exhibit symptoms that challenge the notion that conscious awareness directs our behavior. When shown an image through their left eye, split-brain patients cannot name what they have seen, since language facilities are localized on the right side of the brain (the left eye mostly connects to the right hemisphere, and vice-versa). They are, however, perfectly aware of what they have seen, as they can pick the same image out of a lineup of objects.

Split-brain subjects also confabulate, meaning that they construct false narratives in order to rationalize their behavior in light of an abnormal disconnection. That is to say, subjects believe that they consciously intended to do things that they most certainly could not have intended. In a fascinating 1978 study, researchers showed both sides of a patient's brain a different image, simultaneously. One patient was shown a chicken's claw (left) and a pile of snow (right). The patient was then asked to pick two more images from an array that related to the images he had seen. He selected a chicken and a shovel, respectively.  



The patient was then asked why he picked the objects he was chosen, since the verbal faculties of his brain were not aware that he had seen a pile of snow. He explained to the researchers that he had picked the shovel because he had seen a chicken, and you need a shovel to clean out a chicken coop. In another experiment, the same researchers instructed the right side of a patient's brain to laugh. When the patient began laughing, the researchers asked him why, and he told them that he was laughing because he thought they were funny. He had no idea he had been instructed to laugh, yet saw nothing odd about his laughing (Gazzaniga and Ledoux, 1978).

These split-brain experiments show that first of all, our conscious experiences are in fact a product of our physical brain, if for no other reason than interfering with the organ produces alterations of consciousness. Furthermore, the issue of confabulation raises questions about the nature of consciousness, and its relationship to behavior. We see that a person can be made to behave a certain way - and, an instant later, make a conscious report of having performed that behavior for very different reasons. If our experience of consciousness arises as a process of the physical brain, from whence does agency derive? Is consciousness a dictator, a participant or merely a spectator in the production of behavior?

The work of Benjamin Libet in many ways answered these questions. Libet conducted experiments on the temporal space between conscious awareness of apparently self-generated behavior, and the performance thereof. In Libet's experiments, subjects were wired with EEG sensors and then asked to complete a simple, arbitrary motor task. They were then presented with a button that they were told could be pushed to change that image to a new one. The EEG would be attuned to activations of the brain area associated with the simple motor task of pressing the button. The subjects, meanwhile, were asked to note the time at which they first decided to press the button.



Libet's researchers discovered something startling: the neural pathways associated with the motor activity of button pressing were firing significantly before the subjects reported deciding to press the button. This means that subjects became consciously aware of their desire to press the button only after deciding to press it. This supposedly internally-directed and non-stimulated response was not being driven by anything conscious or independent. Libet's experiments support a perspective called epiphenomenalism, which suggests that consciousness arises as a side effect of neural activity, and plays no active role in the direction of behavior.

When I first encountered Libet's experiments in Daniel Dennett's Consciousness Explained, I realized just how confused—and, frankly, dualistic—my thinking on consciousness had been. I had, of course, implicitly assumed that consciousness was the seat of agency. That is to say, I thought that the impetus to perform apparently voluntary behaviors arose from an independent consciousness. In that view, conscious desire to perform an action must occur prior to the action. According to the work of Libet, that may not be the case. Consciousness or stream of thought is a secondary phenomenon that follows an unconscious mental action. It appears to be an artifact of memory encoding; a way to both contextualize and store information, as well as to separate it from internally- and externally-stimulated behavior.  

The sensation of "I meant to do that," or the mental state of intentionality, is a slippery one. How it is produced, and what its precise functions are, are not questions that are easily answered within today's scientific and philosophical paradigms. It does appear, however, that I was mistaken to assume that the same neural mechanism that registers the sensation of intentionality is responsible for the formulation and production of the impulse to act.

Furthermore, as in the case of split-brain patients, it is possible to see how intentionality can be compounded by each of us with involuntary behaviors, which are accompanied by a sense of being entirely unforced. The evidence of this confusion—and the lack of obvious relationship in relatively simple motor tasks between conscious intentionality, and behavior amongst a non-clinical population—is captured well by Libet's experiments. That his findings carry over to more complex behaviors, and even to the realization of our personalities, is unproven. I suspect that more complex behaviors would produce similar, if not identical results to Libet's work. Experiments along these lines will become more viable as imaging technology improves. By clarifying the role that consciousness and intentionality play in the production of behavior, we learn a tremendous amount about ourselves, and take a step forward in logically resolving fundamental questions about the ways that both normal and pathological brains interface with the world.