PSYB65H3 Lecture Notes - Lecture 9: Amobarbital, Temporal Lobe, Language Development

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18 Nov 2012
Lecture 9
Left Hemisphere
- in LH damage caused by bullet wounds 100% had some aphasic (language) symptoms
- 30% would show some recovery of varying degrees
=> all left-handed or ambidextrous individuals that were able to recover
=> least amount of recovery in right-handed individuals
- LH must be involved in language bc 100% showed some form of damage
- RH damage caused by bullet wounds showed very few language problems, and rarely lead to a form of aphasia
=> those who did show aphasic ppl were all left handed or ambidextrous
=> most of the patients showed recovery from the language problems
- right handed ppl w a bullet wound to the RH – no aphasic symptoms
=> in right handed ppl language is located in the LH
- in left handed ppl language is bilaterally – represented in both sides => damage to either side disrupts language
Language development:
- in children under the age of 5, damage to either side has equal probability of inducing aphasic symptoms
=> some language found on both sides of the brain in children
- in addition, 100% of children will show some degree of recovery
- either side can take over the function of language after brain damage => language is not yet lateralized
- over development language slowly becomes lateralized to one side
=> when children have brain damage on one side of the brain, language is found on the other side of the brain
- some neuropsychologists suggest that left handed ppl are the result of brain damage in childhood
- brain is very plastic during dev’t and loses plasticity as it matures
=> especially around 2-3 – children cant remember anything before that
- in infants brain damage can be treated by removal of the damaged parts of the brain
=> the remaining parts of the brain take over
*at birth both hemispheres are capable of language acquisition
=> LH seems to become more dominant for language with maturity
Acollosal patients:
- patients born w/o a corpus callosum have language on both sides in the adult brain
- during dev’t LH actively suppresses the RH => bc in acollosal patients language remains on both sides
- if hemispheres can’t communicate, some language stays on the RH => active suppression when LH can communicate w
RH, or if LH is damage and can’t suppress, RH will remain w language ability
- LH suppression not as active in left-handed ppl, bc some language remains on RH
Anatomical differences:
Planim temporale: primary language area in temporal lobe; larger, more convoluted and heavier on the left side, by about
=> suggests LH speech area is more equipped anatomically to handle language bc larger in size
- in other apes left temporal lobe was also larger and heavier than the right – not just in humans
=> also true in other animals that communicate, such as birds – vocalization controlled by the LH
- appears that genetic predisposition for animals that communicate to have vocalization to lateralize to the LH
=> also true for left handed ppl – anatomical adv for LH, even though language on both sides
- also seen in infants, and fetuses at 10-31 weeks of gestation
=> larger temporal lobes not caused by experience of speaking – genetic/evolutionary predisposition
Normal humans:
- hippocampus buried deep inside the temporal lobe – may need to be removed to stop seizures in epilepsy (common area
for seizures)
- sodium amytal test done before surgery – injected into one side or the other, and takes a couple minutes before it reaches
the whole brain
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