PROJECTIONS FROM VISUAL AREAS OF THE CEREBRAL-CORTEX TO PRETECTAL NUCLEAR-COMPLEX, TERMINAL ACCESSORY OPTIC NUCLEI, AND SUPERIOR COLLICULUSIN MACAQUE MONKEY

The purpose of this study was to analyze the projections from visually related areas of the cerebral cortex of rhesus monkey to subcortical nuclei involved in eye-movement control; i.e., the pretectal nuclear c omplex, the terminal nuclei of the accessory optic system (AOS), and t he superior colliculus (SC). The anterograde tracer H-3-leucine was pr essure injected bilaterally into the cortex of six monkeys (for a tota l of 12 cases) involving the primary visual cortex (area 17); the medi al prestriate cortex (medial 18/19); dorsomedial area 19; the caudal p ortion of the cortex of the superior temporal sulcus, upper bank (cyto architectural area OAa) and lower bank (area PGa); the lower bank of t he caudal lateral intraparietal sulcus (area POa); and the inferior pa rietal lobule (area 7). The results revealed that the pretectal nucleu s of the optic tract received inputs from medial prestriate cortex, do rsomedial part of area 19, OAa, and PGa. The posterior pretectal nucle us received sparse projections from area 7 and the cortex lining the i ntraparietal sulcus (dorsomedial part of area 19 and POa). The pretect al olivary nucleus was targeted by neurons in cortex of dorsomedial ar ea 19, and the anterior pretectal nucleus was targeted by neurons in b oth dorsomedial 19 and area 7. The nuclei of the AOS (dorsal terminal; lateral terminal; and interstitial nuclei of the superior fasciculus, posterior and medial fibers) received projections exclusively from ar eas OAa and PGa. Furthermore, in one case with PGa injection, the medi al terminal nucleus, dorsal portion, was also labeled. The visual cort ical areas studied projected differentially upon the SC laminae. The p rimary visual area 17 projected only to the superficial laminae, i.e., stratum zonale (SZ), stratum griseum superficiale (SGS), and stratum opticum (SO). On the other hand, the medial portion of the prestriate cortex and caudal OAa and PGa targeted the superficial and intermediat e laminae, i.e., SZ, SGS, SO, and stratum griseum intermediale (SGI), whereas caudal area POa projected primarily to the intermediate layer SGI. Rostral area 7 (mainly 7b) neurons terminated in the stratum albu m intermediale (SAI); no SC terminals were found in a case in which ca udal area 7 (mainly 7a) was injected. (C) 1995 Wiley-Liss, Inc.