Caudate intracellular response to thalamic and cortical inputs

Intracellular recordings of cat caudate neuronal responses evoked by stimulation of the cerebral cortex or of a number of thalamic sites were made. The predominant response was an EPSP-IPSP sequence. A higher percentage of “pure” EPSPs were recorded from the stimulation of centromedian-parafascicular region than from stimulation of other thalamic sites. The outcomes of these experiments were generally in agreement with recent reports concerning the fine structure of the caudate nucleus. The combined anatomical and physiological data suggest that the great majority of striatal input fibers are excitatory and the majority of interneurons are inhibitory in their synaptic effects.