Partitioning of the primate intraparietal cortex based on connectivity pattern and immunohistochemistry for Cat-301 and SMI-32.

We propose a partitioning of the primate intraparietal sulcus (IPS) using immunoarchitectural and connectivity criteria. We studied the immunoarchitecture of the IPS areas in the capuchin monkey using Cat-301 and SMI-32 immunohistochemistry. In addition, we investigated the IPS projections to areas V4, TEO, PO, and MT using retrograde tracer injections in nine hemispheres of seven animals. The pattern and distribution of Cat-301 and SMI-32 immunostaining revealed multiple areas in the IPS, in the adjoining PO cleft and in the annectant gyrus, with differential staining patterns found for areas V3d, DM, V3A, DI, PO, POd, CIP-1, CIP-2, VIPa, VIPp, LIPva, LIPvp, LIPda, LIPdp, PIPv, PIPd, MIPv, MIPd, AIPda, AIPdp, and AIPv. Areas V4, TEO, PO, MT, which belong to different cortical streams of visual information processing, receive projections from at least twenty different areas within the IPS and adjoining regions. In six animals, we analyzed the distribution of retrogradely labeled cells in tangential sections of flat-mount IPS preparations. The lateral bank of the IPS projects to regions belonging both to the ventral (V4 and TEO) and dorsal (PO and MT) streams. The region on the floor of the IPS (i.e., VIP) projects predominantly to dorsal stream areas. Finally, the medial bank of the IPS (i.e., MIP) projects solely to the dorsalmedial stream (PO). Therefore, our data suggest that ventral and dorsal streams remain segregated within the IPS, and that its projections to the dorsal stream can be further segregated based on those targeting the dorsolateral versus the dorsomedial subdivisions.

Cortical visual areas in monkeys: location, topography, connections, columns, plasticity and cortical dynamics.

The visual system is constantly challenged to organize the retinal pattern of stimulation into coherent percepts. This task is achieved by the cortical visual system, which is composed by topographically organized analytic areas and by synthetic areas of the temporal lobe that have more holistic processing. Additional visual areas of the parietal lobe are related to motion perception and visuomotor control. V1 and V2 represent the entire visual field. MT represents only the binocular field, and V4 only the central 30 degrees-40 degrees. The parietal areas represent more of the periphery. For any eccentricity, the receptive field grows at each step of processing, more at anterior areas in the temporal lobe. Minimal point image size increases towards the temporal lobe, but remains fairly constant toward the parietal lobe. Patterns of projection show asymmetries. Central V2 and V4 project mainly to the temporal lobe, while peripherals V2 (more than 30 degrees) and V4 (more than 10 degrees) also project to the parietal lobe. Visual information that arrives at V1 projects to V2, MT and PO, which then project to other areas. Local lateral propagation and recursive loops corroborate to perceptual completion and filling in. Priority connections to temporal, parietal and parieto-temporal cortices help construct crude early representations of objects, trajectories and movements.