CEREBRAL RESPONSE TO PYRAMIDAL TRACT STIMULATION IN WOOD RATS AND ITSRELATION TO LABORATORY RATS

The cerebral response evoked by stimulation of the bulbar pyramidal tr act in wood rats, like that of laboratory rats, consisted of a small a lpha wave, almost obscured by a very large, superimposed r wave. The a lpha wave behaved like a purely antidromic response, whereas the r wav e behaved like a postsynaptic response, including a marked variability in amplitude on repeated trials. The contralateral forepaw and hindpa w motor sites mapped onto the somatic sensory foci for these two paws; further examination showed that the somatic sensory and motor represe ntations were largely superimposed. An incipient sagittal fissure 1.5 mm lateral to the midline marked the boundary between limbic and neoco rtex. Because of their structural similarities and their differences i n somatic sensory and motor organization, wood rats and laboratory rat s are prime subjects for comparative study of the role of amalgamated and separate sensory and motor cortices in regulating movement and beh avior.