#9. The Two–test-tube Experiment: Part I [neuroscience]

Your Brain is Like This.

NE

Red, theory; black, fact.

The the motivating challenge of this post is to explain the hemispheric organization of the human brain. That is, why we seem to have two very similar brains in our heads, the left side and the right side.

Systems that rely on the principle of trial-and-error must experiment. The genetic intelligence mentioned in previous posts would have to experiment by mutation/natural selection. The synaptic intelligence would have to experiment by operant conditioning. I propose that both these experimentation processes long ago evolved into something slick and simplified that can be compared to the two–test-tube experiment beloved of lab devils everywhere.

Remember that an experiment must have a control, because "everything is relative." Therefore, the simplest and fastest experiment in chemistry that has any generality is the two-test-tube experiment; one tube for the "intervention," and one tube for the control. Put mixture c in both tubes, and add chemical x to only the intervention tube. Run the reaction, then hold the two test tubes up to the light and compare the contents visually (Remember that ultimately, the visual system only detects contrasts.) Draw your conclusions.

My theory is basically this: the two hemispheres of the brain are like the two test tubes. Moreover, the two copies of a given chromosome in a diploid cell are also like the two test tubes. In both systems, which is which varies randomly from experiment to experiment, to prevent phenomena analogous to screen burn. The hemisphere that is dominant for a particular action is the last one that produced an improved result when control passed to it from the other. The allele that is dominant is the last one that produced an improved result when it got control from the other. Chromosomes and hemispheres will mutually inhibit to produce winner-take-all dynamics in which at any given time only one is exposed to selection, but it is fully exposed. 

These flip-flops do not necessarily involve the whole system, but may be happening independently in each sub-region of a hemisphere or chromosome (e.g., Brodmann areas, alleles). Some objective function, expressing the goodness of the organism's overall adaptation, must be recalculated after each flip-flop, and additional flip flopping suppressed if an improvement is found when the new value is compared to a copy of the old value held in memory. In case of a worsening of the objective function, you quickly flip back to the allele or hemisphere that formerly had control, then suppress further flip flopping for awhile, as before. 

The foregoing implies multiple sub-functions, and these ideas will not be compelling unless I specify a brain structure that could plausibly carry out each sub-function. For example, the process of comparing values of the objective function achieved by left and right hemispheres in the same context would be mediated by the nigrostriatal projection, which has a crossed component as well as an uncrossed component. More on this next post.