Brain Connectivity in Ateles geoffroyi: Resting-State Functional Magnetic Resonance Imaging of Working Memory and Executive Control.

The objective of this research was to describe the organization and connectivity of the working memory (WM) and executive control (EC) networks in Ateles geoffroyi in resting-state conditions. Recent studies have shown that resting-state activity may underlie rudimentary brain functioning, showing that several brain regions can be tonically active at rest, maximizing the efficiency of information transfer while preserving a low physical connection cost. Whole-brain resting-state images were acquired from three healthy adult Ateles monkeys (2 females, 1 male; mean age 10.5 ± SD 2.5 years). Data were analyzed with independent component analysis, and results were grouped together using the GIFT software. The present study compared the EC and WM networks obtained with human data and with results found in the literature in other primate species. Nine resting-state networks were found, which were similar to resting networks found in healthy human adults in the prefrontal basal portion and frontopolar area. Additionally, components of the WM network were found to be extending into the hypothalamus and the olfactory areas. A key finding was the discovery of connections in the WM and EC networks to the hypothalamus, the motor cortex, and the entorhinal cortex, suggesting that information is integrated from larger brain areas. The correlated areas suggest that many elements of WM and EC may be conserved across primate species. Characterization of these networks in resting-state conditions in nonhuman primate brains is a fundamental prerequisite for understanding of the neural bases underlying the evolution and function of this cognitive system.

Tractography of the spider monkey (Ateles geoffroyi) corpus callosum using diffusion tensor magnetic resonance imaging.

The objective of this research was to describe the organization, connectivity and microstructure of the corpus callosum of the spider monkey (Ateles geoffroyi). Non-invasive magnetic resonance imaging and diffusion-tensor imaging were obtained from three subjects using a 3T Philips scanner. We hypothesized that the arrangement of fibers in spider monkeys would be similar to that observed in other non-human primates. A repeated measure (n = 3) of fractional anisotropy values was obtained of each subject and for each callosal subdivision. Measurements of the diffusion properties of corpus callosum fibers exhibited a similar pattern to those reported in the literature for humans and chimpanzees. No statistical difference was reached when comparing this parameter between the different CC regions (p = 0.066). The highest fractional anisotropy values corresponded to regions projecting from the corpus callosum to the posterior cortical association areas, premotor and supplementary motor cortices. The lowest fractional anisotropy corresponded to projections to motor and sensory cortical areas. Analyses indicated that approximately 57% of the fibers projects to the frontal cortex and 43% to the post-central cortex. While this study had a small sample size, the results provided important information concerning the organization of the corpus callosum in spider monkeys.

Cerebral Anatomy of the Spider Monkey Ateles Geoffroyi Studied Using Magnetic Resonance Imaging. First Report: a Comparative Study with the Human Brain Homo Sapiens / Anatomía Cerebral del mono araña Ateles geoffroyi estudiada utilizando imágenes de resonancia magnética. Primer reporte: estudio comparativo con el cerebro humano Homo Sapiens

The objective of the present qualitative study was to analyze the morphological aspects of the inner cerebral anatomy of two species of primates, using magnetic resonance images (MRI): spider monkey (A. geoffroyi) and human (H. sapiens), on the basis of a comparative study of the cerebral structures of the two species, focusing upon the brain of the spider monkey and, primarily, its limbic system. In spite of being an endemic Western hemisphere species, a fact which is by its own right interesting for research due to this animal’s social organization and motor functions, the spider monkey (A. geoffroyi) has hardly been studied in regard to its neuroanatomy. MRI was carried out, in one spider monkey, employing a General Electric Signa 1.5 T scanner. This investigation was carried in accordance to international regulations for the protection of animals in captivity, taking into account all protective means utilized in experimental handling, and not leaving behind any residual effects, either physiological or behavioral. From a qualitative point of view, the brains of the spider monkey and the human were found to have similar structures. In reference to shape, the most similar structures were found in the limbic system; proportionally, however, cervi cal curvature, amygdala, hippocampus, anterior commissure and the colliculi, were larger in the spider monkey than in the human.

El objetivo del presente estudio cualitativo fue analizar los aspectos morfológicos de la anatomía cerebral interna utilizando imágenes de resonancia magnética (IRM) en dos especies de primates, El mono Araña (A. geoffroyi) y el humano (H. sapiens), tomando como base un estudio comparativo de las estructuras cerebrales de las dos especies, concentrándose primordialmente en el sistema límbico del cerebro del mono araña. Aunque es una especie común en el hemisferio occidental, es interesante para estudiar dada su organización social y funciones motoras, el mono araña (A. geoffroyi) ha sido poco estudiado en cuanto a su neuroanatomía. Las IRM fueron hechas a un mono araña utilizando un resonador General Electrics Signa 1.5 T. Esta investigación se llevo a cabo conforme a las leyes internacionales para la protección de animales en cautiverio y teniendo en cuenta todas las medidas de protección para el manejo experimental para evitar cualquier efecto residual de índole comportamental o fisiológico. Desde un punto de vista cualitativo, los cerebros del mono araña y el humano tenían estructuras similares. Con respecto a la forma, las estructuras más parecidas fueron encontradas en el sistema límbico, sin embargo la curvatura cervical, la amígdala, el hipocampo, la comisura anterior y el colículo fueron más grandes proporcionalmente en el mono araña que en el humano.