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					Language & Consciousness
Lecture 27

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

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

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

Language: Cortical Localization
Broca’s Area Production

B

W

Left Hemisphere

Wernicke’s Area comprehension

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

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

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

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

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

Cat Neuroanatomy

CC

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

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

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

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

LVF

RVF

L

Speech Body

Mute Body

R

LVF

RVF

Normal subject CC intact


What did you see? an apple ~

LVF

RVF

L

Speech

R

LVF

RVF

Normal subject


What did you see? a cow info to Left via CC ~

LVF

RVF

L

Speech

Mute

CC

R

LVF

RVF

Split-brain CC cut


What did you see? a cup ~

CC

LVF

RVF

L

Speech

R

LVF

RVF

Split-brain
What did you see? Nothing  Why not? ~


CC

LVF

RVF

L

Speech

Mute

CC

R

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

LVF

RVF

Split-brain

L

Speech Body

Mute Body

R

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

LVF

RVF

L

Speech

Mute

CC

R

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

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

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


				
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posted:1/29/2010
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