Language &Consciousness

Lesson 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 ~

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 & Consciousness Experiment

put one hemisphere asleep• Sodium amytal

Right hemisphere asleep object in right hand (behind back) can verbally ID

Left hemisphere asleep In R. hand no verbal memory In L. hand can ID by touch ~

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

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 ~

Speech Mute

Body Body

L R

LVF RVF

Normal subjectCC intact

LVF RVF

What did you see?

~

Speech

L R

LVF RVF

What did you see?

info to Left via CC ~

Normal subject

LVF RVF

Speech Mute

L RCC

LVF RVF

CC

Split-brainCC cut

LVF RVF

What did you see?

~

Speech

L R

LVF RVF

CC

Split-brain

LVF RVF

What did you see?

~

CCSpeech Mute

L R

LVF RVF

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. by touch ~

Split-brain

Speech Mute

Body Body

L R

LVF RVF

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.”

Like Clive Wearing’s writing His explanation: “unconscious writing”

Simultaneous lateralized inputs? ~

Speech Mute

L RCC

LVF RVF

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.

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 ~