Ives@MIT-MULTICS.ARPA (03/14/84)
A strikingly clear picture of brain parallelism at the gross anatomical level was presented during a lecture at MIT on the architecture of the cerebral cortex by a neuroanatomist (Dr. Deepak Pandya, Bedford Veterans Administration Hospital, Bedford, MA). Almost a hundred years ago, dye studies showed that the cerebral cortex is not a random mass of neurons, and it was mapped into a few dozen areas, differentiated by microstructure. Later, it was shown that lesions in a certain area always produced the same behavioral deficiencies. Now, they have mapped out the interconnections between the areas. The map looks like a plate of spaghetti but, when transformed into a schematic, reveals simplicity and regularity. Each half of the brain includes six sets of areas. Each set has a somatic area, a visual area and an auditory area. Each area in a set connects to the other two, forming a triangle. The six sets form a stack because each area is connected to the area of the same kind in the next set. The eighteen areas schematicized by this simple triangular stack include most of the tissue in a cerebral cortex. If I remember correctly, all mammals have this architecture. It was surmised that one set evolved first and was replicated six times, because the neuronal microstructure varies gradually with increasing level. He also suggested that higher levels might process higher levels of abstraction. -- Jeffrey D. Ives