Wednesday, November 26, 2008

Strange Brain Games

There are numerous examples of curious and wonderful mental abilities that seem to be unleashed in damaged brains. Perhaps the most famous of these is the memory abilities of Kim Peek, the man on whom the movie "Rainman" was based. Kim was born without a corpus callosum which is the main trunk of nerves connecting the left and right brain hemispheres. He is severely disabled--although he can walk and talk, he cannot dress himself or take care of himself in some very basic ways. But his feats of memorization are amazing. He can read a page of text and remember it, word for word, years later. He has memorized several thousand books, maps, telephone directories, etc. He can, for example, respond, within a few seconds, with block by block directions for driving from an obscure street address in one of some 200 U.S. cities to another obscure street address in a distant city. He can report the succession of Catholic popes over the past 2000 years, from St. Peter to the present day, giving their names, their dates, and historical information about them; similarly, for all the kings of England and all the presidents of the U.S. (including their vice presidents and the members of their cabinets).

Kim is not a so-called "idiot savant" since he has a known brain disfigurement. The term "idiot savant" was historically applied to severely mentally and emotionally disturbed individuals who appeared to have normal brains from a neuroanatomical standpoint. These people are now generally diagnosed as "autistic"; they are cared for by their families or in mental institutions around the world. Most autistic patients do not have special mental abilities--they are not "savants." But some can do elaborate mathematical calculations in their heads, remember dates or zodiacal positions covering centuries, and perform other amazing mental abilities.

Some people who are not significantly emotionally or socially disabled can perform equally amazing mental feats. One young man, while attending college, displayed his memorization of 22,500 decimal places of the numerical constant pi. (Pi is the Greek letter used to refer to the ratio of a circle's diameter to its circumference. The digits of pi extend indefinitely without repeating; they have been calculated by computer to several billion decimal places. Pi begins 3.14159265....) Or consider the young college man who could calculate irrational numbers in his head to approximately 100 decimal places. (Irrational numbers are numbers, such as pi or the square root of two, that cannot be written as the ratio between two integers. Their decimal digits extend indefinitely without repeating themselves. There is an infinite number of irrational numbers. A hand calculator will commonly calculate irrational numbers to 10 decimal places; a larger, lab calculator may be able to go to 20 or 30 decimal places. It is an extraordinary feat to calculate an irrational number to 100 decimal places even with the largest electronic computer.)

Another young man, in this case severely emotionally and mentally disabled, can be flown a single time over a large city and proceed to draw from memory a detailed picture of the city from a sky view, including the winding streets, locations and appearances of buildings, down to such details as the size and locations of trees and roof-top ventilators: literally hundreds of thousands of precise details.

We must assume that each of our brains is capable of such feats, but that these abilities have been inhibited in order to provide for the panorama of normal brain functions. One woman reported that she was "plagued" by the ability to remember every minute of every day of her life since she was a young child. This ability was, for her, a terrible burden and impediment to normal functioning.

How does the brain remember? One leading theory says that as an event is first perceived, the visual, auditory, and other inputs from that perception trigger the release of certain transmitter hormones between a few of the billions of nerve-cell branches in our brains. The new nerve-cell connections that are formed (in a pattern reflecting the original perceptions) may be weak (and soon forgotten) or strong (and remembered). They may be reinforced by repeating the same or similar perceptions (learned). The original event can be "remembered" by reawakening, through internal or external stimulation, the pattern of neuronal connections that was formed by the original perceptions.

What about memory, that is, conscious recall? How and when these neuronal patterns that recreate the original events are allowed into consciousness is another matter altogether. It is the job of another part of the brain to sort through and select among restimulated internal neuronal patterns, and allow into consciousness only those that are needed and can be productively worked on in consciousness by our higher, most complicated and sophisticated abstracting and connecting tools that reside there.

Thus many complex mental activities and would-be memories are censored from our conscious review so that we can proceed in an orderly and focused way along an otherwise baffling life path.