RESUMEN
We studied the organization of the inferior parietal cortex (IPC) in five capuchin monkey (6 hemispheres) using cytoarchitectonic (Nissl), myeloarchitectonic (Gallyas), and immune-architectonic (SMI-32 monoclonal antibody) techniques. We partitioned the IPC into five distinct areas: PFG, PG, Opt, PFop, and PGop. Since we used parasagittal sections, we were not able to study area PF due to its far lateral position, which yielded slices that were tangential to the pial surface. Areas PFG, PG, and Opt were in the convexity close to the lateral sulcus, while PFop and PGop were positioned more posteriorly, in the opercular region of IPC. Of all the five regions, area Opt was the one most similar to its analogue in the macaque, especially as revealed with SMI-32 staining. Namely, in both primate species area Opt showed a low density of large pyramidal neurons. Additionally, the apical dendrites of these neurons were sparse and vertically orientated, resembling columns. We also found area PG to be similar: both species exhibited cell body layers with a radial arrangement. On the other hand, Nissl staining revealed area PFG to be architectonically different between New and Old-World monkeys: PFG in the capuchin showed a comparatively higher cell density than in macaques, especially in layers II and IV. These results suggest that evolution may have enabled the functional specialization of these brain regions based on behavioral demands of upper limb use. The small differences in the IPC of the two primates may be linked to interspecies variability.
Asunto(s)
Cebus , Lóbulo Parietal , Animales , Macaca , Neuronas/fisiología , Mapeo EncefálicoRESUMEN
Cebus monkeys stand out from other New World monkeys by their ability to perform fine hand movements, and by their spontaneous use of tools in the wild. Those behaviors rely on the integration of somatosensory information, which occurs in different areas of the parietal cortex. Although a few studies have examined and parceled the somatosensory areas of the cebus monkey, mainly using electrophysiological criteria, very little is known about its anatomical organization. In this study we used SMI-32 immunohistochemistry, myelin, and Nissl stains to characterize the architecture of the parietal cortical areas of cebus monkeys. Seven cortical areas were identified between the precentral gyrus and the anterior bank of the intraparietal sulcus. Except for areas 3a and 3b, distinction between different somatosensory areas was more evident in myelin-stained sections and SMI-32 immunohistochemistry than in Nissl stain, especially for area 2 and subdivisions of area 5. Our results show that cebus monkeys have a relatively complex somatosensory cortex, similar to that of macaques and humans. This suggests that, during primate evolution, the emergence of new somatosensory areas underpinned complex manual behaviors in most Old World simians and in the New World cebus monkey. J. Comp. Neurol. 524:1399-1423, 2016. © 2015 Wiley Periodicals, Inc.