Somatotopic organization of caudate-caudate relationships in the cat

Experiments were carried out on cats locally anesthetized and paralyzed with Flaxedil. Stimulation of the caudate nucleus and the sciatic nerve evoked biphasic positive-negative field potentials in the contralateral nucleus with mean latencies of 16.1 +/- 1.8 msec and 18.1 +/- 1.6 msec, and peak to peak amplitudes of 185.5 +/- 19.8 microV and 236.9 +/- 11.5 microV, respectively. A mediolateral distribution was observed in the caudate connections. The medial and lateral halves of one nucleus project to medial and lateral halves of the contralateral caudate, respectively. However, maximum amplitude responses were grouped in the middle-external two-thirds of the caudate. No responses could be evoked in the caudate tail by stimulation of any part of the opposite nucleus. On the other hand, the somatic afferents are distributed to all levels of the caudate nucleus. Although the largest responses were recorded in the same areas where the highest potentials were evoked by contralateral caudate stimulation. It is concluded that, in the cat, a topographic organization of the caudate-caudate relations exist in the mediolateral axis of the nucleus, and that its middle regions could be the primary receptive fields for caudate and somatic afferents.