Cortical connections of the motor thalamic nuclei in the Japanese monkey, Macaca fuscata.

Our findings revealed the nucleus ventralis lateralis pars oralis (VLo) projection to motor area, and the nucleus ventralis anterior pars principalis (VApc) projections to the premotor and supplementary motor areas (SMA). The VLo gave rise to thalamocortical projections terminating in the superficial half of layer I, mainly in the forelimb motor area. The VApc gave rise to the superficial projections to the post-arcuate premotor area around the arcuate genu and arcuate spur as well as SMA. We suggested that the medial pallidal segment projects to the motor area via VLo, and to the premotor area and SMA via VApc. We also proposed that the premotor area and SMA receive cerebellar afferents via nucleus ventralis lateralis pars caudalis and area X.