This brief study was made as a corollary to previous experimental work on additional motor areas of the macaque monkey. The region of the island cortex is shown in figures 6A and B, as it relates to the opercular areas of the matching cerebrum. Although there is not general agreement as to the homology of the insula (von Bonin and Bailey, '47, Frontera, '56) of monkey with that of man, it appears that two varieties of cortex can be distinguished in both. Von Bonin and Bailey ('47) describe agranular cortex at the limen as the dominant histologic feature, although some granular cortex is found in the caudal part of the insula. Several authors (von Bonin and Bailey, '47; Kaada, Pribram and Epstein, '49 and Kaada, '51) emphasized the presence of discernible rostra1 motor cortex and caudal sensory cortex in the island.Frontera's ('55) description of the macaque insula will be used as reference here. Branches of the middle cerebral artery divide the island into a dorsorostral portion and a ventrocaudal portion without there being evidence of true gyri and sulci ( fig. 6A). The dorsorostral insula is covered by the frontoparietal operculum of the Walker ('40) areas 6, 4, and 1, and the ventrocaudal region by the temporal operculum of area 22 of the superior temporal gyrus ( fig. 6B).
TEN FIGURESThis study was made to explore a cortical region that developed to a high degree in animals which are dependent upon large olfactory connections. The cingulate gyrus has remained a sizeable cortical convolution in primates and a few other mammals in which the olfactory pathways are small o r vestigial. This gyms ( fig. 1, A) encircles the subdivisions of the corpus callosum, extending from the sulcus of the corpus callosum to the sulcus cinguli. The anterior portion of the gyrus (Walker-Brodmann areas 24, 25 ; Walker, '40) contains agranular cortex (Rose and Woolsey, '48) similar to the motor area of the precentral gyrus. The authors just quoted described the posterior portion of the gyrus (areas 23, 29 and isthmus) as possessing granular cortex similar to the sensory area of the postcentral gyrus.
METHODS AND MATERIALSThe observations and testing of 16 Macaca wzulatta monkeys included an evaluation of the certain items preoperatively and postoperatively. These items were ternperaturc, pulse and respirations, conscious level, sensory modalities, motor and secretory activity and emotional behavior.Grateful acknowledgement is givcn to the Parke-Davis Pharmaceutical Company for the monkeys provided f o r this experimentation.
a
SIX FIGURESThis study is concerned with certain functions of the medial nucleus of the dorsal thalamus and the way in which these are reflected by its various connections within the nervous system. This work tends to emphasize that this nucleus is a part of a complex motor and sensory system involving connections with the central nervous system at hemisphere and brain stem levels. For documentation of this statement the results of stimulation and ablation experiments are reported and correlated with the underlying anatomical relations as revealed by a study of the brains of the animals operated upon in these experiments.
METHODS AND MATERIALSThe microscopic anatomy of the brain of Macaca mulatta was investigated in order to establish the normal topography of the areas involved experimentally. The material studied was from the Huber Neurological Collection. A normal series of sections of the brain had been stained by the Weil technique and a companion series stained with toluidin blue. These provided a correIative comparison of nuclei and fiber tracts in the various parts of the brain. This paper is based on a thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the University of Michigan.*The work was assisted by grants from the Walter C. Hill Fund and animals provided by the Parke, Davis Pharmaceutical Company for which the writer wishes t o express appreciation.
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