Recruiting response in caudate nucleus

Abstract

Responses in the caudate nucleus, induced by a single shock and low-frequency stimulation of the thalamus, were investigated in the cat under barbiturate anesthesia. The responses could be induced from the nonspecific thalamic nuclei excepting the ventral portion of centrum medianum. Low-frequency stimulation of these nuclei induced a recruiting response that consisted of two components, i.e., large and small positive potentials. The large component showed a recruitment of amplitude and was suppressed by high-frequency stimulation of the mesencephalic reticular formation (MRF). Furthermore, the amplitude of the component became smaller or indiscernible with little evidence of recruitment after extensive cortical ablation or after the cortical application of postassium cyanide solution. The small component showed no recruitment of amplitude and was not influenced by MRF stimulation or by cortical ablation. A single shock to nuclei medialis dorsalis, lateralis dorsalis, or anterior medialis and ventralis could induce responses but the responses were not altered by repetition of the stimulation at low frequency, nor were they influenced by MRF stimulation or by cortical ablation. These findings suggest that the small component is derived from the same origin as the response induced by a single shock and that it is elicitable via a direct projection from the thalamus to the caudate nucleus, while that of the large component depends upon activity of the cortex.