Descrição anatômica macroscópica do encéfalo de primatas neotropicais e citoarquitetura neocortical de Sapajus Libidinosus (primatas: cebidae)

Abstract

The human brain is the most sophisticated instrument of cognition and, putatively, the most complex material sctructure ever knew, probably because that, the neural system is largely studied in multidisciplinar terms, but many questions still need to be answered and various doubts rest to be solved about the brain functions. Among the ways to understand this evolutionary history is the study of the non-human primate encephalon. Much is known about the gross anatomy of Old World Primates and humans, however, these data and those related to the microscopic anatomy are scarce compared to the neotropical, which has been widely used in biomedical and behavioral research. In order, the purpose of this work was to study the gross anatomy of the brain obtained from neotropical primates as Callithrix penicillata, Saimiri ustus, Sapajus libidinosus e Brachyteles arachnoides and from literature from Galago, Macaca, Papio, Pan and Homo, in comparative terms. In addition to conducting a preliminary study on the neocortical cytoarchitecture of Sapajus libidinosus. In gross anatomy were used 2 brains of Callithrix penicillata, 1 of Saimirius ustus, 7 of Sapajus libidinosus and 1 Brachyteles arachnoides, which have their sulcus and gyri described, measured, as well as measurements of the general dimensions of the encephalon and encephalization index. For the microscopic analysis, 5 brains of Sapajus libidinosus were used, 4 in the Golgi-Cox method and 1 in the HE method, which were evaluated in terms of cytoarchitectonic organization, number of neural cells and classification of the cortex according to type and cell prevalence in cortical layers, frontal, prefrontal area, parietal, temporal and occipital areas. In this study, it was observed that the gross anatomy telencephalon of Callithrix and Saimiri have few sulcus and gyri when compared to Sapajus and Brachyteles, and the latter two are more similar to the Old-World primates than of the other neotropical primates investigated. Among all the primates analyzed and compared, the repeats sulcus are the longitudinal, lateral, calcarino, hippocampus, rinal and superior temporal sulci. The sulci of the frontal lobe and parietal lobe appear only in more complex brains and animals that have larger body size. The other structures located in the medial region of the telencephalon, diencephalon, midbrain, pons, bulb and encephalic ventricles are similarly arranged with variations in the degree of development and size. Preliminary data from Sapajus neocortical architecture show higher numbers of neurons in the occipital lobes, followed by the parietal and temporal lobes. The caudal part of the frontal lobe has features of primary motor area with large pyramidal neurons and the prefrontal area has a prevalence of granular neurons. The parietal and temporal lobes have the most heterogeneous layers and with greater separation between the cortical layers. The Golgi-Cox method allowed the study of the structural organization, connections between neural cells and neural cell forms, and the HE method allowed quantitative inferences and also the characterization of neural cell types and development of the cortical layers. The histological analyzes of the neocortex of the main areas of the Sapajus libidinosus telencephalon, even with a low number of specimens, was a general characterization and the first step for future studies and more comprehensive comparisons. More detailed histological studies of the main areas are necessary as well the association of these possibles results with other investigative techniques for a better characterization of the functionalities of the cortical areas.