Thalamocaudate projection neurons with a branching axon to the cerebral motor cortex

Sixty-nine thalamocaudate projection neurons in ventroanterior (VA: 32 cells), centrolateral (CL: 12 cells) and centrum medianum or parafascicular (CM-Pf: 25 cells) nuclei of the cat were identified by antidromic response to stimulation of the caudate nucleus (CD). Twenty-two VA and 3 CL neurons in this sample were proved to have a branching axon projecting on both CD and the cerebral motor cortex (Mcx). Most of the branching VA neurons showed repetitive discharges synchronous with the cortical recruiting response elicited by repetitive stimulation (6-10/sec) of the pallidum. Such activities of the VA neuron which would induce the motor cortical recruiting response, were proved to be conveyed to CD.