Inferior frontal eye field projections to the pursuit-related dorsolateral pontine nucleus and middle temporal area (MT) in the monkey

Abstract

Inferior frontal eye field (FEF) projections to the dorsolateral pontine nucleus (DLPN), and corticocortical connections with the superior temporal sulcal (STS) cortex, were studied in five macaque monkeys which had received horseradish peroxidase (HRP) gel implants into the inferior prearcuate cortex (including area 45 of Walker, 1940). These connections were contrasted with those from the dorsal FEF (area 8a) in another macaque monkey. Findings of heavy inferior FEF projections to the ipsilateral DLPN (light to the contralateral DLPN) and reciprocal connections with the deep caudal bank and fundus of the superior temporal sulcus (STS), presumed to be the middle temporal (MT) visual area (Maunsell & Van Essen, 1983a), appeared to go hand in hand with more pronounced projections to the stratum superficialis of the superior colliculus (SC). In contrast, the HRP gel implant in the dorsal prearcuate cortex (area 8a of Walker, 1940) resulted in only very light projections to the ipsilateral DLPN, more pronounced projections to the dorsomedial pontine nucleus (DMPN), almost no projection to the stratum superficialis (SS), and more pronounced reciprocal connections with the upper bank of the STS, presumed to be the medial superior temporal (MST) area (Maunsell & Van Essen, 1983a). Both the inferior and dorsal FEF also had extensive reciprocal connections with the ventral intraparietal area (VIP; Maunsell & Van Essen, 1983a) in the caudal bank of the intraparietal sulcus. The correlated projections of the inferior FEF to the DLPN, MT area, and SS may explain its reported role in smooth pursuit (Lynch, 1987), in addition to its well-established role in the production of voluntary purposeful saccadic eye movements (Bruce et al., 1985).