17Su11Lec11

17Su11Lec11 - Cogs17 Neurobiology of Cognition Summer 2011...

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Cogs17 Neurobiology of Cognition Summer 2011 Lecture 11: Language and Lateralization Lateralization = Dominance of one hemisphere of cerebral cortex over the other for particular functions - Determined in part by Wada Test = Anesthetize 1 hemisphere by injecting Sodium Amytal in L or R carotid artery - Right hemisphere is usually dominant for visio-spatial tasks and socio-emotional processes (see more below) - Left hemisphere is usually dominant for language & other sequential and analytic processes - Includes manual control: ~90% humans are right-handed , even prehistorically (per early tools, artwork, etc.) - Planum Temporale - area in Temporal Cortex ( includes Wernicke’s Area ) - larger in Left Hemisphere - In Nonhuman Primates: Equal or only slightly larger in left, also involved in vocal communication - Right Cerebral Cortex slightly larger in Males , Left Cerebral Cortex slightly larger in Females - As we’ve already seen, Crossover of perceptual and motor pathways determines some dominance patterns - VISION: Right Visual Cortex receives from Left Visual Field (from Right Retinas of both eyes) & vice versa - MOTOR: Right hemisphere controls Left half of body (& vice versa); Both control face altho opposite dominant - SOMATOSENSORY: Right somatosensory cortex from Left half of body (& vice versa); Face more shared - Interference can be observed in simultaneous tasks controlled by same hemisphere, or in competition between hemispheres - e.g. While talking (Left hemi dom), will tap more slowly w/Right hand (Left hemi dom), than w/Left hand (Right hemi dom) - e.g. Stuttering (most often in left-handers) may involve hemispheric competition for control of speech - Corpus Callosum = Bundle of axons connecting 2 cortical hemispheres integrate sensory/motor info from 2 sides - Thicker in Left Handers (who also tend to be more ambidextrous than right-handers) - Thicker in Women , who are thus less lateralized (e.g. after damage to one hemi, other more able to take over function) - Split-Brain Patients have Corpus Callosum connections severed - e.g. As treatment for epilepsy - Word or image flashed in Right Visual Field (=> Left hemi) can be ID’d by touch only by Right hand but not by Left hand - Image flashed in Right Visual Field (=> Left hemisphere) easily named, but not if in Left Visual Field - Image (e.g.
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17Su11Lec11 - Cogs17 Neurobiology of Cognition Summer 2011...

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