Projections from the globus pallidus to the thalamic areas projecting to the dorsal area 6 of the macaque monkey: a multiple tracing study.

In the brains of 3 Japanese monkeys (Macaca fuscata), a combined injection of the tract-tracers Fast Blue (FB), Diamidino Yellow (DY), and horseradish peroxidase-conjugated with wheat germ agglutinin (WGA-HRP) was performed: the retrograde tracers, FB and DY, were injected into a rostral and a caudal sectors of the dorsal part in area 6, and the anterograde tracer, WGA-HRP, was injected into the internal segment of the globus pallidus (GPi). In the thalamus, FB- and DY-labeled neurons were distributed in a segregated manner. A substantial number of the FB-labeled and DY-labeled thalamic neurons were located within the thalamic areas containing fine axons labeled with WGA-HRP. The results suggest that the GPi may project to both the rostral and caudal sectors of the dorsal part of area 6 through the thalamus.