Horseradish peroxidase studies on thalamic and striatal connections of the mesial part of area 6 in the monkey.

In monkeys (Macaca fuscata), horseradish peroxidase (HRP) was injected in the mesial part of area 6a alpha and 6a beta of the Vogts (presumed supplementary motor area). Groups of retrogradely labelled neurons were found in the dorsolateral half of VA, VLc, X and VLm. Other groups of retrogradely labelled neurons extended through Pcn, Csl, the dorsal edge of Cn.Md, Pf, Cl, MDmf, MDdc and MDpc in the thalamus and the claustrum. Anterogradely labelled terminals were found in turn in these thalamic portions. The neostriatum, the claustrum and the medial part of pars parvocellularis of the red nucleus were noted to receive dense anterogradely labelled terminals. These connections are similar to those of the dorsolateral part of area 6 (premotor area) with some topographical differences.