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Lecture 19

Lecture 19

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Human Biology
John Yeomans

HMB200H1S L19; March. 20, 2012 Cortex: From Limbic to Association Cortex go from 3 layers to 6 layers, very difficult to DEFINE. How it evolved from limbic cortex to association cortex! Evolution of Cerebral Cortex how layers have evolved Subcortex: e.g. basal ganglia, extended amygdala. Paleocortex: e.g. basal forebrain, olfactory. Archicortex & transitional: e.g. medial prefrontal, insular, hippocampus. Limbic cortex: orbitofrontal, cingulate, parahippocampal. Primary neocortex: Motor, somatosensory, visual, auditory. Association neocortex: Frontal, Parietal, Temporal. Cortex Types Distribution of functional zones in relation to Brodmanns map of human cortex Start w motor cortex to frontal pole. then started in center again & went to posterior area Mammalian brain has large Neocortex recently discovered o Sometimes called Isocortex only found in mammals, not birds o 2mm thick Blue = Primary Cortical Areas Layers of neocortex Paleocortex: 0.5mm thick, 3 layers o After primary is higher order assn cortex = combo of senses Association: gets a lot of cortical input, outer layers = thicker, primary working together o A1 has connection w speech cortices inner layers = thinner? Green = Limbic Transitional: includes hippocampus (evolved from paleocortex, o Old, thin slightly thicker), orbitofrontal cortex which evolves to primary cortex o Cingulate gyrus, parahippocampal gyrus, temporal pole, into Primary: difficult for anatomists to find these layers o Can see layers III & IV dominant here since receiving direct frontal cortex thalamic visual & auditory input o Pyriform cortex = Olfactory cortex Other sensory cortex like visual & somatosensory o 2mm thick? Evolution: Green Blue Yellow Pink Cerebellar cortex: 3 layers o Limbic Primary Unimodal assn Higher assn Anatomical Definitions Oldest dortex = Basal Forebrain Colonoergic 0.5mm, thinnest cortex HMB200H1S L20; March. 21, 2012 Speech and Language Paleocortex: 3 layers o Gradual transition to 6 layers as layers added on over long time Bird Song and Left Hemisphere Transitional cortex: 36 layers. o Hippocampus = highly developed, has 3 or 4 layers Limbic: Visceral inputs (taste, olfaction, hypothalamus, dopamine). Primary neocortex: Somatic inputs from thalamus. o Layers 4 & 5 dominate. o Evolved from hippocampal to 6 layers Association neocortex: Corticaland non-primary thalamus inputs (mediodorsal n, pulvinar) Brodmanns Areas (1-42) Go thru neurogenesis in spring, degredation in winter Testosterone helps regeneration in left hemisphere sing differently each summer for male courtship calls Growth only on left side of brain lateral fn o idea that speech is lateralized in left hemisphere Human Aphasias 97% have left hemisphere injury. o Injury to Brocas Area = Brocas Aphasia o 3% right hemisphere injury Brocas Tan. No ifs, ands, or buts Wernickes Aphasia. Lots of meaningless words. o Poor understanding, and recovery. o Fluent speech but poor comprehension Wernickes Theory of Speech and Reading. Werkicke-Gershwind model: o Sound reaches ear auditory system processes the sounds neaural signals reach auditory cortes o Sounds dont become words unless identified by Werknickes Area o To repeat the words: Word-based signals sent from Wernickes to Brocas via Arcuate Fasciculus muscular movement for speech (go to motor cortex) o Visual info can reach Brocas w/o going thru angular gyrus Broca`s Aphasia: o Can produce words w HIGH MEANING & poor grammar o Speaking very gradually o Writing is NOT consistent o Lack Flow within sentences o Can't say many words Damage to Arcuate fasciculus Conduction aphasia o = PRODUCTION APHASIA inability to produce words. o Hard to repeat speech Temporal Lobe damage includes Wernicke`s Area o Speech problems o Don't understand speech well Output from Arcuate fasciculus, arching around Sylvian fissure Brocas speech info processed o Damage to auditory association cortex in temporal lobe, includes Brocas organizes speech patterns ventral parietal lobe. Both B & W lesioned many losses within brain o MEANINGLESS SPEECH o Global Aphasia o Able to speak perfectly Learn language from mothers, presented in auditory mode o Can easily say "No, ifs, ands and buts!"
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