[Retrograde degeneration of the pyramidal cells in the motor cortex of apes (Macaca fascicularis)]

Abstract

In three adult macaques the retrograde degeneration of cell bodies in the motor cortex was investigated 6 months after unilateral pyramidal tract section. Large and small Betz cells of the fifth layer were identified microscopically and counted. The analysis of the data reveals that after pyramidotomy, (1) contrary to our expectations from the extent of the pyramidal lesions, a surprising percentage of undegenerated Betz cells remains in the contralateral motor cortex, (2) a greater percentage of small rather than large cell survives, and (3) the greatest loss of cells is in the foot region, the smallest in the face region. The results are discussed in relation to the role of pyramidal axon collaterals in the survival of cell bodies, and the distinction between pyramidal cells and pyramidal tract cells.