Cortical Projections of Cat Medial Thalamic Cells

Abstract

In order to clear up the long debated question of the medial thalamic projections to the cortex, it was necessary to explore the structures at the unitary level and to make use of antidromic cell activations. The present work has made it obvious. The principal fact that has been acquired by this technique is the demonstration of a direct connection between the medial thalamus and certain cortical areas. However, this connection seems to arise only from the anterior part of the CM-Pf complex, with the majority of its cells of origin situated in the nucleus centralis lateralis. Such a connection can explain the relatively short latency observed when stimulations are applied to the CM-Pf nucleus and evoked potentials are recorded at the cortical level from the same sites at which stimulating electrodes have been placed in the present experimental series (Albe-Fessard & Rougeul, 1957). However, in this former work, such short latencies (0.5 ms) as those in some antidromic experiments could never be found. We suggest that it is because well localized bipolar electrodes were then applied at Ant 7.5, in the most posterior medial thalamic zones, and that from there connections to cortex are made through a final relay situated in anterior CM-Pf or n. centralis lateralis.