Projections from Caudal Ventrolateral Prefrontal Areas to Brainstem Preoculomotor Structures and to Basal Ganglia and Cerebellar Oculomotor Loops in the Macaque

The caudal part of the macaque ventrolateral prefrontal (VLPF) cortex hosts several distinct areas or fields—45B, 45A, 8r, caudal 46vc, and caudal 12r—connected to the frontal eye field (area 8/FEF). To assess whether these areas/fields also display subcortical projections possibly mediating a role in controlling oculomotor behavior, we examined their descending projections, based on anterograde tracer injections in each area/field, and compared them with those of area 8/FEF. All the studied areas/fields displayed projections to brainstem preoculomotor structures, precerebellar centers, and striatal sectors that are also targets of projections originating from area 8/FEF. Specifically, these projections involved: 1) the intermediate and superficial layers of the superior colliculus; 2) the mesencephalic and pontine reticular formation; 3) the dorsomedial and lateral pontine nuclei and the reticularis tegmenti pontis; and 4) the body of the caudate nucleus. Furthermore, area 45B projected also to the regions around the trochlear nucleus and to the raphe interpositus. The present data provide evidence for a role of the caudal VLPF areas/fields in controlling oculomotor behavior not only through their connections to area 8/FEF, but also in parallel through a direct access to preoculomotor brainstem structures and to the cerebellar and basal ganglia oculomotor loops.