Abstract
Postsynaptic potentials (PSPs) of cat motoneurons were investigated by intracellular recording of unit activity during stimulation of the motor cortex unilaterally or bilaterally. Synaptic activation of motoneurons by ipsilateral cortical influences requires stronger stimulation than by contralateral and the PSPs thus produced differ from the contralateral in their longer latent period and segmental delay time. Stimulation of the ipsilateral cortex inhibits EPSPs and IPSPs of motoneurons evoked by contralateral cortical stimulation. Global activity recorded on the dorsal surface of the spinal cord is simultaneously depressed. It is concluded from the analysis of the data that inhibitory interaction between two descending cortical activities takes place with the participation of the segmental inhibitory interneuronal apparatus and is brought about at the level of interneurons and (or) through hyperpolarization changes in the membrane potential of the motoneurons themselves.
Published Version
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