Asymmetry in the cerebral cortex of Macaca fascicularis: A basal substrate for the evolution of brain mechanisms underlying language.
Item
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Title
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Asymmetry in the cerebral cortex of Macaca fascicularis: A basal substrate for the evolution of brain mechanisms underlying language.
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Identifier
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AAI9521270
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identifier
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9521270
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Creator
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Gannon, Patrick John.
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Contributor
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Adviser: Jeffrey T. Laitman
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Date
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1995
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Language
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English
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Publisher
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City University of New York.
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Subject
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Anthropology, Physical | Biology, Neuroscience | Language, General
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Abstract
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A central question in anthropology involves the evolution of brain substrates underlying human language. This study tests the hypothesis that these substrates have a long evolutionary history within primates and were present in basal form in the common ancestor of cercopithecoids and hominoids, if not earlier. In humans, left hemisphere cortical areas which subserve language functions are asymmetric, being larger than their contralateral homotypes. These human language areas have homologs in the cerebral cortex of macaques. This dissertation investigates whether human-like patterns of asymmetry are present in macaques.;Unlike previous studies, all brain specimens of Macaca fascicularis (n = 44) were fixed in situ by trans-cardiac perfusion to control for fixation-induced artifact. Further, the application of new techniques and incorporation of a series of new measures allowed for more precise delineation of subtle patterns of brain asymmetry. Measures of cortical structures associated with language region homologs were made both directly from brains (n = 18) and from brain photographs (n = 34). New measures used included the dimensions of sulci deep to the surface of the brain. Included were the arcuate, central and superior temporal sulci, sylvian fissure, surface features of adjacent cortical gyri, frontal and occipital petelias and frontal and parietal hemispheric widths.;Results showed that dimensions of frontal lobe structures deep to the brain's surface were significantly larger in the left hemisphere while brain surface structures tended to be larger in the right. Petelial patterns and co-occurrence were similar to humans, while hemispheric widths were symmetric. Some measures showed marked sex differences; for example, left central sulcus depth was significantly larger only in females (P = 0.05), and the height of the vertical limb of the right arcuate sulcus was significantly larger only in males (P = 0.04).;The patterns of asymmetry seen in the cerebral cortex of macaques indicates a mosaic of neural substrates organized somewhat different to humans. Although the vocal-auditory channel has become the primary modality in humans, this may not be the case for non-human primates. Accordingly, these neural mechanisms probably reflect a species-specific pattern of incorporation into a functional substrate which subserves primarily visual-gestural communication.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
