First thoughts

The quest to understand consciousness in neuroscientific terms is, in my opinion, one of the most fascinating and puzzling that scientific enquiry has yet come across. What is consciousness, and what neural activity in a brain is part of it? How do we tell from looking at third-person data what a brain is experiencing ? Why is that neural activity identical to an experience and some other neural activity is not (e.g. automatic responses and reflexes mediated by the spinal cord)? Do infants, animals, end-stage Alzheimer's patients, etc.  experience anything at all? What part of your brain are you in (or is that a silly question)? What gives rise to the mental phenomena that we experience at the first-person, subjective level, such as having a song "stuck in your head" and having a thought "come to mind" or "occur to oneself"? Can brain scans tell us "what it is like" to be a dog (if dogs have consciousness)? Does a middle C sound the same to me as it does to you? What pathways in the brain are essential for sensory experience, and what thoughts about sensory data can occur without any perception? (e.g. is it possible for someone in an unusual state such as brain damage or dissociative drug intoxication to see or hear something and start thinking at an abstract level about how it got there or what it is without even perceiving it?) How can we tell the difference between I) a combination of a green square and a blue circle, and II) a combination of a blue square and a green circle? Can there be a continuum between dysexecutive syndrome and paralysis, if various parts of the so-called motor hierarchy are damaged? How is it possible to experience your own emotions, even though the projections from the limbic system to the cortex don't appear to be processed in a manner like sensory perception? These (and similar) questions are the ones that fascinate me most, and also the ones that, in my opinion, a neuroscientific answer to which constitutes progress toward, or part of, an explanation of consciousness. If all (or almost all) of these questions can be answered, I will consider our understanding of consciousness to be satisfactory.

Let me begin by considering the question of what part of your brain you are in by means of a thought experiment. Let's say we flash a bright light at you, and record the responses of the neurons all over your brain. The information goes from the retina through the optical nerve, then the thalamus, then the primary visual cortex, then to subsequent areas being processed and processed, and then...you see it.

Suppose I could selectively "block off" those pathways by temporarily disabling the neurons in a specific region. Let's say I flashed the light at you, and "isolated" your primary visual cortex V1 (in the back of the brain) from the rest of your brain by blocking all its projections to those parts until 1 second after the flash, and then allowed it to interact with the rest of the brain again, and after a further few seconds, asked you "Did you see it?". You would probably say "no". Now suppose I placed the "blockage" around a larger area of your brain surrounding V1, and did the same thing, and kept encompassing larger and larger areas. Eventually, I would be doing what would amount to "sectioning off" just a small piece in the front of your brain. At what point would you say you "saw" it? I would argue that it makes sense to define the location of the brain that you actually saw the flash based on this question.

Note however that it is important that the "blockage" be removed before you are asked if you saw the flash. Otherwise, you could simply be unable to report the experience because you cannot control the part of your brain responsible for speech (Broca's area) due to its being "sectioned off" or didn't actually hear the questions asked. By removing the blockage, we make sure that these issues don't arise and we can thus address the question of where in the brain the experience of seeing the flash occurred.

We could of course do an analogous thing for the other senses. For instance, we could present some sound (say that of running water) to you while "sectioning off" your auditory cortices (A1) until one second after the sound ends, and then remove the blockage, wait a moment, and ask if you heard it. And then we could repeat the experiment while moving the "blockage" so as to encompass increasingly large areas of the cerebral cortex surrounding A1 in each hemisphere, until you responded with a "yes".

If it turns out that in fact the experiences all occur in some area of the brain (which may of course be large, even encompassing more than 50% of the cortex) then, I argue, it makes sense to say that is where you are.

To be continued at a later date...