Language & Consciousness Lesson 27

Lateralization of Function n 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 ~

Lateralization: Language n 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 ~

Language & Consciousness n Experiment l put one hemisphere asleep Sodium amytal n Right hemisphere asleep l object in right hand (behind back) l can verbally ID n Left hemisphere asleep l In R. hand  no verbal memory l In L. hand  can ID by touch ~

Mind/Brain Relationship n 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? ~

Split Brain Research n 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 ~

Animal Research n 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? ~

CC Cat Neuroanatomy

Discrimination Training n 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 ~

Discrimination Training n 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? ~

Human Split-Brain Research n 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 ~

Human Split-Brain Research n 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 ~

Speech Mute Body LR LVF RVF

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

Speech LR LVF RVF

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

Speech Mute LR CC LVF RVF

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

Speech LR LVF RVF

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

CC Speech Mute LR LVF RVF

I.D. by R. Hemisphere n 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. by touch ~

Split-brain Speech Mute Body LR LVF RVF

Paul - Mr. P.S. n Split-brain patient n R. & L. hemi language l spell w/ L. hand using scrabble letters n “I know it wasn’t me that did that.” l Like Clive Wearing’s writing l His explanation: “unconscious writing” n Simultaneous lateralized inputs? ~

Speech Mute LR CC LVF RVF

n 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 ~ Paul - Mr. P.S.

n 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? ~

The Nature of Consciousness n 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 ~