Dane Bramage


 


OK, time for some Irresponsible Speculation™.
I finished listening to another enjoyable book, Friends, Lovers, Chocolate , by Alexander McCall Smith--a solid, thoughtful writer who makes me want to live in Edinburgh--that threw in the possibility of cellular memory. In this case, it was visions that might be arising from a transplanted heart.

It was just enough to get me musing on one of my favorite strange facts--that from the age of 2 to about 10 the brain loses neurons and synapses . From before birth two about two years, the brain grows, adding neurons and synapses at a rapid rate, and so the process from 2 to 10 can with some justification be called 'pruning.'

The process is a straightforward one: at the start of a task, you equip yourself with all the tools and resources you think you might need, and then put aside the excess as the parameters of the job become clear. And indeed, after pruning, there are fewer neurons, but each neuron has far more synapses--and the mature neurons get themselves protected by a myelin sheath absent in earlier stages. All very nicely done.

Only--what does that mean for the mind?

We have, thank goodness, gone beyond the stuff I was taught in high school--the brain is a big computer and the neurons simply switches. The fact alone that there are multiple neurotransmitters working the synapses tends to ruin that model, as well as thee fact that there's no CPU--and, more important, no programmer. How do neurons store data--that is, memory? If they store it in anything like switches--with open and closed gates--then what sort of data do all those billions of neurons and synapses blooming in this inflationary universe of infancy? If they're empty, how does the brain know they're empty? How does the mind know? And if they're not, what's in them?

We're in an interesting position here: if memory is stored purely by synapse position and connectivity, we have, in the infant brain, tons of information not based on experience; if it's not strictly that, then there is at least a partial molecular basis for memory--and memory, or at lest aspects of memory, could be stored elsewhere than in the nervous system--and that could lead to ghost images from a transplanted heart.

Fortunately I'm not about to solve problems that could very well be answered by experimentation. (you know, the way I solve the philosophical problems of the ages.) When the sun goes down and the dogies are in the corral, I'm more interested in a good starting point for an SF story than proving myself smarter than those pesky neurobiologists.

So here goes:
• The first and most venerable speculation is the Wordsworthian idea that the infant has got to forget its pre-existence in heaven. And it may be that the brain has got to expand itself to a certain complexity, like a flower, to capture a soul. And that in turn might imply that souls are not dropped down the chute on purpose, but is snagged in their flitting about by the fetal brain. Once captured, however, the extra petals are not needed, and so can be shed as the soul wraps itself in the nervous system, creating a mind.
• Following the unfortunate computer/program metaphor, we tend to think that consciousness is created, if not from a list of code, then at least from silence and neutrality. It might be that consciousness requires a kind of neural chaos in which to arise. Of course with all sorts of random and quasi-random events that wholesale creation of neurons implies, the fact that it ends up at the same thing--consciousness--is pretty amazing (if, of course, consciousness can be called a 'thing'.)
• Or to look at it the other way, it may be consciousness itself that starts the pruning. Since consciousness can be described as a kind of focus, as a kind of selection, that it selects from the broad functionality of the infant brain and prunes off the useless resources. ("Use it or lose it" does seem to be an operating neurological principle.) That in turn leads one to wonder what unused resources are there in the inflationary infant mind--and if there is a way to tap them. The old saw about 'using only 5% of our brain--now seen as a fatuity if not a falsehood--might in fact be true of the infant brain.
• When contemplating Alzheimer's, one might ask how the young brain can systematically lose brain cells and yet have consciousness, memory, symbol manipulation and oh, just all sorts of other stuff be enhanced. Over and above curing the disease that causes it, might the other processes that accompany pruning preserve, if not restore, the mind's functioning in the aged?
• The fact that self-awareness seems to come into being only after the peak of raw brain complexity is achieved seems to cast doubt on the idea that consciousness might arise spontaneously from a complex enough network. Might complexity beyond a very precise level--and of a very precise nature, perhaps--impede the development of self-awareness? Might there be a required resonance to be achieved?
•
There. that was fun. And if any eminent neuroscientists come across this little post and are reduced to high dudgeon, don't get mad--get even. I'll post any responses that don't include citations from the Bell Curve. Truly, madly, deeply, there's nothing I like better than to be proved wrong, if I learn by it.

Posted: Sunday - January 14, 2007 at 09:10 AM        

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