PSYCH 15 Lecture Notes - Lecture 12: Auditory Cortex, Primary Motor Cortex, Motor Cortex
Chapter 16: Lateralization, Language, and the Split Brain Circuits
- Major difference between the functions of the left and right cerebral hemispheres
- Cerebral commissures connect the halves of the brain
- Split-brain patients have been studied to understand what happens when these connections are
severed
- Discovery of the specific contributions of left-hemisphere damage to aphasia and apraxia
o Aphasia – deficit in language comprehension or production due to brain damage, usually on the
left
o Boa’s aea – left inferiori prefrontal cortex, damage leads to expressive aphasia
o Apraxia – difficulty performing movements when asked to do so out of contexts, also a
consequence of damage on the left
▪ If told to dik a up of offee adoly whe ot thisty, they wo’t e able to do it;
a do it if they’e told to whe they’e thisty
o Both are associated with damage to the left hemisphere
o Language and voluntary movement seem to be controlled by one half of the brain, usually the
left
o Suggests that One hemisphere is more dominant than the other
- Tests of cerebral laterialization
o Sodium amytal test: anesthetize one hemisphere and check for language function
o Dichotic listening test: report more digits heard by the dominant half
o Functional brain imagine: fMRI or PET used to see which half is active when performing a
language test
- Discovery of the relation between speech laterality and handedness
o Left hemisphere is speech dominant in almost all dextrals (right-handers) and most sinestrals
(left-handers)
- Corpus Callosum is the largest cerebral commissure
o Transfers learned information from one hemisphere to the other
o When cut, each hemisphere functions independently
- Myers and Sperry studied split-brain cats
o Transected the carpus callosum and optic chiasm so that visual information could not cross to
the contralateral hemisphere
o By blindfolding one eye of the cat, they restricted the visual information to the hemisphere
ipsilateral to the uncovered eye
o Look at graph and the 50% to 100%
- Commissurotomy in human epileptics
o limits convulsive activity
o many never have another major convulsion
o sperry and gazzaniga
▪ developed procedures to test split-brain patients
o differs from split-brain animals in that the 2 hemispheres have very different abilities – most
left hemispheres are capable of speeh, while the ight ae’t
- Evidence that the hemispheres of split-brain patients can function independently
o Present a picture ot the right visual field (left brain)
▪ Left hemisphere can tell you what it was
▪ Right had a show you, left had a’t
o Present a picture to the left visual field (right brain)
▪ Sujet will epot that he does ’t kow what it was
▪ Left had a show you what is was, ight had a’t
- Cross-cuing
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Document Summary
Chapter 16: lateralization, language, and the split brain circuits. Major difference between the functions of the left and right cerebral hemispheres. Cerebral commissures connect the halves of the brain. Split-brain patients have been studied to understand what happens when these connections are severed. Discovery of the relation between speech laterality and handedness: left hemisphere is speech dominant in almost all dextrals (right-handers) and most sinestrals (left-handers) Corpus callosum is the largest cerebral commissure: transfers learned information from one hemisphere to the other, when cut, each hemisphere functions independently. Cross-cuing: facial feedback from the other hemisphere, for example: the right hemisphere might make the face frown when the left hemisphere gives an incorrect spoken answer. Doing 2 things at once: each hemisphere of a split-brain patient can learn independently and simultaneously, helping hand phenomenon, dual foci of attention, chimeric figures task. Angular gyrus: agraphia: inability to communicate through writing or spell, alexia: inability to see words or read.
