MICROELECTRODE STUDIES OF AFFERENT CONNECTIONS AND EFFERENT PROJECTIONS OF NEURONS IN SENSORIMOTOR CORTEX OF CAT

The functional anatomy of neurons of cat sigmoid gyrus has been studied. Simultaneous recording with four microelectrodes in pre- and postcruciate cortex was carried out. Various inputs were investigated with regard to their ability to evoke the same cortical unit. Stimulation sites included: primary sensory receiving area (S1); ventrolateral nucleus of the thalamus (VL); center median (CM); red nucleus (RN); as well as pyramid and pes pedunculi. Following classification of units as pyramidal tract (Pt) neurons or, as units not identifiable as pyramidal tract (nPt) neurons, they were compared with regard to their response to stimulation at the sites listed above. In addition to Pt neurons, units were antidromically evoked by stimulation of S1, VL, and RN but not by stimulation of CM. The Pt and nPt neurons were observed to project to S1, but no Pt neuron projected to VL. Neurons with output to VL were not evoked by stimuuation of RN. The Pt neurons, orthodromically evoked by VL stimulation, did not respond, but some nPt neurons did respond to input from S1. The Pt neurons orthodromically evoked by single-pulse stimulation of CM were not evoked by stimulation of VL. Some convergence of synaptic input on Pt neurons from S1 and CM was observed. There was convergence of inputs from VL and CM on the majority of nPt neurons studied. © 1968.