Fiber connections between the dorsal thalamus and corpus striatum in the cat

Abstract

An attempt was made to establish the projection of fibers from the caudate nucleus and to determine the efferent fiber connections from certain nuclei of the dorsal thalamus to the basal ganglia. Single, unilateral, electrolytic lesions were placed in the head of the caudate nucleus, and in the dorsomedial, centromedian, or lateral thalamic nuclei of the cat. Sections were stained by the Nauta silver impregnation method for degenerated nerve fibers. It was shown that the caudate nucleus contributes fibers to the globus pallidus, nucleus subthalamicus, and the rostral portion of the substantia nigra pars reticulata; however, the caudate does not appear to contribute fibers to the putamen or the dorsal thalamus. Results of a previous investigation of the basal ganglia necessitated a further study of the dorsal thalamus in relation to the corpus striatum. The dorsomedial nucleus of the thalamus sends fibers into the adjacent thalamic nuclei; the majority of fibers course rostrally into the nucleus ventralis anterior and nucleus reticularis and a smaller number to the caudate nucleus. The centromedian nucleus contributes fibers to the globus pallidus and putamen, and a small number of fibers are sent to the head of the caudate nucleus. It also contributes a number of fibers to the nucleus ventralis lateralis, nucleus dorsomedialis, nuclei of the mid-line, a few fibers to the same nuclei of the opposite side, and a number of fibers rostrad to the reticular and the anterior thalamic nuclei. The globus pallidus sends fibers into the nucleus ventralis lateralis of the dorsal thalamus through the field H1 of Forel. Since the nucleus ventralis lateralis of the dorsal thalamus contributes fibers to the medial and intralaminar nuclei and these nuclei discharge to the caudate, putamen, and globus pallidus, a circuit is established whereby the dorsal thalamus is interrelated with striatal activity directly, and indirectly through the anterior and reticular thalamic nuclei and through the cortex.