Thursday, March 22, 2007

The Brain, the Mind, and the Self

A Brief Tutorial from the Neuroscience Perspective (deliberately ignoring Philosophy, see below)

Brain: an organ of soft nervous tissue contained in the skull of vertebrates, functioning as the coordinating center of sensation and intellectual and nervous activity

Mind: the element of a person that enables them to be aware of the world and their experiences, to think, and to feel; the faculty of consciousness and thought

Self: a person’s essential being that distinguishes them from others, especially considered as an object of introspection; from Brok’s dictionary definitions (taken from New Oxford)

In a first year grad school course on drug abuse, we were asked by the professor why people take abused drugs. My classmate and I, the only two neuroscience students in the class, responded "because of what they do to the brain - their pharmacological sites of action affect areas of the brain involved in euphoria and habit formation, etc." "NO, people take drugs because of how it makes them FEEL!" was the retort from a psychology student. Nevermind that there are mountains of evidence (cf TE Robinson) that mammals who habitually use drugs do not "like" the drug anymore (in science-speak, rodents and primates develop tolerance to the euphorigenic effects of abused drugs after repeated drug exposures), but neverthless crave it. No, the correct response is, "You don't FEEL ANYTHING independently of your brain!!!" (At least, not in our mortal bodies.) One's perception of the world occurs entirely through that organ at the top of your body.

[Fun fact: The adult human brain is about 2% of body weight. A cat's brain is 0.8% of its body weight. This is why I call my kitty "pea-brain" and often mock her ability to process info.]

If you’ve ever held a human brain in your hands, as I have, you know that it is not very impressive – only about three pounds or so, the size of the clenched fists of an average man, just tissue with a few spaces (sulci and the ventricles). And yet, this organ is responsible for what we know of ourselves and our environment. And all this organ really does is move ions around.

Think about it (move some potassium and sodium around in the cerebral cortex of your right hemisphere). Imagine yourself walking with a loved one on a sidewalk along the beach and gazing out at the horizon. Suddenly your fingers, which are running along a rail, contact a piece of gum. The information about that object is running up your fingers, hand, and arm, to your spinal cord, through the brain stem, through the reticular formation into your thalamus, and then to areas of the somatosensory cortex, then back to motor cortex and cerebellum and down through the brain stem to move your fingers off of the gum, at the same time as your visual cortex and motor cortex are sending information to the cerebellum to plan the movement of your head and then sending motor signals through the accessory nerve (XI) so that your eyes can look at the gum you have touched (through the oculomotor nerve (III) and trochlear nerve (IV), then back through the optic nerve (II)); from the thalamus, info is being sent to your hippocampus to sort through prior experiences that are similar to the current tactile sensation; your limbic system and associated cortex are 'deciding' what 'emotion' you 'feel' about this experience, and then relaying that out to motor areas to change your facial expressions through the facial nerve (VII) - we are social creatures, after all; and information is also coasting to Broca’s area and then back out to the nerves connected to muscles of the mouth, lips, and tongue so that you can say something to your loved one about what you have just touched. See how long it took you to read that? Your nervous system does this in fractions of a second through nothing more than moving around some Ca2+, Na+ and K+

Take out parts of the hippocampus, and you’d forget who you are. Remove parts of your posterior parietal association cortex, and you wouldn't recognize your limbs as belonging on your body. How do we integrate all these different parts into a 'self' that we are aware of?

He said, "It's all in your head," and I said, "So's everything," but he didn't get it. - Paper Bag, Fiona Apple

Broks' writes: “We continually, and effortlessly, picture each other’s thoughts and intentions. We form assessments of what people ‘have in mind’ – presupposing that there are such things as minds…The same mental machinery enables us to form ideas of ourselves as unified and continuous beings – to make sense of what is going on with regard to our own mental states. People with impoverished mind-reading skills (such as autistic people), or with rich but unreliable interpretations of their own and others’ mental activities (like schizophrenics) are severely disadvantaged.” And yet schizophrenia is most likely attributable to a complex organization of impaired cholinergic and glutamatergic transmission in cortical regions of the brain (cholinergic and glutamatergic receptors are cation channels once activated). Autism may be the result of abnormalties of cell size and transmission in the temporal lobes of the brain and the limbic system. If we look closely enough, can we understand mind and self?

[I'm largely ignoring philosophical perspectives on the mind and body, as science completely rejects dualistic thinking and more recent theories focus on whether and/or how empiricism can be used to understand the mind (see Colin McGinn's arguments that humans may lack the cognitive ability to understand the mind; philosophers like Daniel Dennett and neuropsychologists like Hebb argue the opposite) and not-yet-developed methods to understand the brain's function (see John Searle and Thomas Nagel).]

According to one researcher, as humans developed language, areas of the brain became involved in forming a cohesive narrative of one’s life experience, ultimately generating a sense of ‘self.’ Maybe neuroscientists will one day prove Buddhism correct? (I'm being facetious.)

When considering questions of mind and self from a neurobiological perspective, we must take into account the following factors:

unity nature of consciousness: we experience the world as a sum, not all the parts separately

intentionality: our experiences have meaning that the mind collects and represents over the range of our lifetime

subjectivity: our experience of the same stimulus differs. Far from being machine-like, our minds deal with semantics like values, sense, and meaning (see Searle). These are inherently subjective.

So where does that leave us? Can neuroscientists find the 'seat' of the self or consciousness, tucked somewhere in cells that are doing nothing much grander than adding up electrical potential from ion concentrations? (Actually neurons, like almost all cells, have receptor areas and second messenger signalling that enhance or diminish their responsivity to inputs and outputs.) Wasn't there a magazine article that claimed neuroscience had disproven the notion of the soul? This is the century of neuroscience, or so it was titled by one popular magazine at the turn of the century. This century will see scientific examinations into the above questions (and hopefully I'll stay employed), and this brief overview is only meant to provide a glance into the issues.

References:

Into the Silent Land: Travels in Neuropsychology (2003) by Paul Broks
Fundamentals of Human Neuropsychology (1996) by B Kolb & IQ Whishaw
Fundamental Neuroscience (1997) ed. DE Haines
Principles of Neural Science (2002) ed. Kandel, Schwartz, & Jessel

6 comments:

ME said...

You should have gone to yesterday's faculty seminar. It was Camillo Padoa-Schioppa (Harvard University) - Neuronal encoding of economic value. It was very interesting and touched upon some of these questions.

AG said...

Me, you know I almost never go to talks with computational neuroscientists. Do you care to share some insights?

Pseudo-Iamblichus said...

We are truly incarnate spirits, are we not?

Thank you for giving us a summary of the nuts and bolts of it all.

CrimsonCatholic said...

More grist for the mill from the quantum-mechanical side, courtesy of A&M's own Dimitri Nanopoulos:
Superstring applications to brain function
Quantum electrodynamic modeling of neuron micro-tubulin

Of course, Nanopoulos doesn't get into the philosophical side of mind/body dualism, but he does have some interesting thoughts on physical consciousness/brain dualism, and that is a huge problem, as you correctly noted.

And now, a moment of silence for the passing of my beloved Aggies from the tournament.







Thank you.

Jonathan Prejean
Fightin' Texas Aggie Class of 1996

AG said...

Microtubules as the seat of consciousness? Say it ain't so! (I hate the way research is conducted in molecular biology.)

Those were fascinating articles, and in the first, Dr. Nanopoulos had me really engaged until Freud! Thanks for sharing them.

The Men's basketball team (sniffle) deserves their own post.

BTW Mr. Prejean (once known as Physics96), we share a few Aggie-related acquaintances. A gentleman who went by the name titan still speaks very highly of you and of your help in a certain, hmm, Calvinist onslaught.

CrimsonCatholic said...

Yeah, I miss both Tony and Steve White (the infamous Calvinist, who was really a good guy if you got to know him). The move to California was kind of sudden, and I got caught up with other things, so I haven't been in touch with them for a while. I remember one time we all went to see The Passion of the Christ in Ft. Worth and went for coffee afterward. Just a great bunch of guys.

I think it was Travis Strow who brought along an Orthodox guy named John (can't remember his last name), who was friends with another Aggie named Perry Robinson. I remember that John said that he "just couldn't get past Aquinas's doctrine of divine simplicity." If I had known then how much time I would spend obsessing about that particular issue over the next several years, I probably would have run screaming from Starbucks. :-)