Abstract
We propose that some of the features of the topographic organization
in motor cortex emerge from a competition among several conflicting
mapping requisites. These competing requisites include a somatotopic
map of the body, a map of hand location in space, and a partitioning
of cortex into regions that emphasize different complex, ethologically
relevant movements. No one type of map fully explains the topography;
instead, all three influences (and perhaps others untested here)
interact to form the topography. A standard algorithm (Kohonen network)
was used to generate an artificial motor cortex array that optimized
local continuity for these conflicting mapping requisites. The resultant
hybrid map contained many features seen in actual motor cortex, including
the following: a rough, overlapping somatotopy; a posterior strip
in which simpler movements were represented and more somatotopic
segregation was observed, and an anterior strip in which more complex,
multisegmental movements were represented and the somatotopy was
less segregated; a clustering of different complex, multisegmental
movements into specific subregions of cortex that resembled the arrangement
of subregions found in the monkey; three hand representations arranged
on the cortex in a manner similar to the primary motor, dorsal premotor,
and ventral premotor hand areas in the monkey; and maps of hand location
that approximately matched the maps observed in the monkey.
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