Language Consciousness Lecture 27 Lateralization of Function Hemispheres

Language & Consciousness Lecture 27

Lateralization of Function Hemispheres specialized l process information differently l L: “analytic” vs R: “holistic” l information shared via commissures n Language l meaning Left hemisphere l emotional content Right hemisphere n Aphasia l language impairments ~ n

Lateralization: Language Evidence from stroke victims n Left hemi. damage l aphasias l paralysis: right side n Right hemi. damage l no aphasias l paralysis: left side n Females less lateralization l unilateral lesion less aphasia ~ n

Language: Cortical Localization Broca’s Area l frontal lobe l motor programs l damage production deficits n Wernicke’s area l Temporal lobe l meaning of words l damage comprehension deficits ~ n

Language: Cortical Localization Broca’s Area Production B W Left Hemisphere Wernicke’s Area comprehension

Language & Consciousness Declarative memory l deficits no conscious memory n Infantile amnesia l < 2 -3 yrs old n WADA test l sodium amytal l anesthetize brain hemisphere l inject left or right jugular ~ n

Language & Consciousness Experiment l put one hemisphere asleep l place object in left hand (behind back) n Right hemisphere asleep l can verbally ID n Left hemisphere asleep l no verbal memory of object l can ID with left hand ~ n

Mind/Brain Relationship Monism l mind product of brain function n Dualsim l fundamentally different and separate n Split brain 2 minds? l commissurotomy l Monism? l Dualism? ~ n

Split Brain Research Commissurotomy l sever corpus callosum n Humans l treatment of severe epilepsy n Animals l also sever optic chiasm l only ipsilateral visual inputs n No communication b/n hemispheres ~ n

Animal Research Myers & Sperry - Nobel prize l 2 consciousnesses in 1 body? n Cats & monkeys l cut corpus callosum & optic chiasm n Completely lateralized visual input l left eye left hemi only l right eye right hemi only n Do hemispheres have different experiences? ~ n

Cat Neuroanatomy CC

Discrimination Training Left eye open n Discrimination training l triangle press button reward l circle press button no reward n After learned cover left eye l no longer performs task l information not available to right hemi n 1 hemi learned association l other one did not ~ n

Discrimination Training Differential training l left: triangle reward l right: circle reward l no pressing for non-rewarded shape n Hemispheres learned different things l separate consciousnesses? ~ n

Human Split-Brain Research Commissurotomy epilepsy tx l optic chiasm intact l no apparent deficits l contralateral visual inputs n Lateralized visual input l Tachistoscope or T-scope l < 200 msec l info to 1 hemisphere ~ n

Human Split-Brain Research Discrimination training l same as animals n Verbal identification of objects l visual l tactile n Other interesting phenomenon l L & R competition l and more ~ n

L LVF RVF Speech Mute Body R

LVF Normal subject CC intact n What did you see? an apple ~ RVF

LVF L Speech RVF R

LVF Normal subject n What did you see? a cow info to Left via CC ~ RVF

L LVF RVF Speech Mute CC R

LVF RVF Split-brain CC cut n What did you see? a cup ~ CC

LVF L Speech RVF R

LVF RVF Split-brain What did you see? Nothing n Why not? ~ n CC

L LVF RVF Speech Mute CC R

I. D. by R. Hemisphere L. Hemi no knowledge of key n How can R. hemi identify? l reach into bag w/ L. hand l I. D. the key n R. hand cannot I. D. ~ n

LVF RVF Split-brain L Speech Mute Body R

Paul - Mr. P. S. Split-brain patient n R. & L. hemi language spell w/ L. hand using scrabble letters n “I know it wasn’t me that did that. ” ~ n

L LVF RVF Speech Mute CC R

Paul - Mr. P. S. Point to the object best related to what you see l R. hand chicken l L. hand shovel n “I saw a claw and I picked the chicken, … and you have to clean out the chicken shed with a shovel. “ n Confabulation ~ n

Paul - Mr. P. S. T-scope to ask questions n Who is your girlfriend? l R & L same answer n Career choice: I want to be a _____. l L. hemi. doctor l R. hemi race car driver n 2 consciousnesses in 1 body? ~ n

The Nature of Consciousness Split-brain split consciousness? n Monism vs. Dualism l How do you split a nonphysical entity? l supports monist view n Brain & Behavior mental states physiological states ~ n