Visual cortical projections and chemoarchitecture of macaque monkey pulvinar

We investigated the patterns of projections from the pulvinar to visual are as V1, V2, V4, and MT, and their relationships to pulvinar subdivisions bas ed on patterns of calbindin (CB) immunostaining and estimates of visual fie ld maps (P-1, P-2 and P-3). Multiple retrograde tracers were placed into V1 , V2, V4, and/or MT in 11 adult macaque monkeys. The inferior pulvinar (PI) was subdivided into medial (PIM), posterior (PIP), central medial (PICM), and central lateral (PICL) regions, confirming earlier CB studies. The P-1 map includes PICL and the ventromedial portion of the lateral pulvinar (PL) , P-2 is found in ventrolateral PL, and P-3 includes PIP, PIM, and PICM. Pr ojections to areas V1 and V2 were found to be overlapping in P-1 and P-2, b ut those from P-2 to V2 were denser than those to V1. V2 also received ligh t projections from PICM and, less reliably, from PIM. Neurons projecting to V4 and MT were more abundant than those projecting to V1 and V2. Those pro jecting to V4 were observed in P-1, densely in P-2, and also in PICM and PI P of P-3. Those projecting to MT were found in P-1-P-3, with the heaviest p rojection from P-3. Projections from P-3 to MT and V4 were mainly interdigi tated, with the densest to MT arising from PIM and the densest to V4 arisin g from PIP and PICM. Because the calbindin-rich and -poor regions of P-3 co rresponded to differential patterns of cortical connectivity, the results s uggest that CB may further delineate functional subdivisions in the pulvina r. J. Comp. Neurol. 419:377-393, 2000. (C) 2000 Wiley-Liss, Inc.