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Canada (492,253)
Psychology (7,600)
PSYB65H3 (519)
Ted Petit (310)
Lecture 9

PSYB65 Lecture 9.doc

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University of Toronto Scarborough
Ted Petit

PSYB65 Lecture 9: Historical overview of left/right hemisphere: -mostly came from observations during war when had large population that obtained wounds to the head (bullet wounds) - depending on where the bullet wounds where would notice different behavioural problems - in adults, left hemisphere damage – 100% will show some aphasic symptoms (problems in language/speech), approx 30% showed recovery in left handed or ambidextrous individuals (both right and left handed); least amount of recovery was in right handed individuals - correct meaning of aphasia is that there is no language and speech at all, but don’t use it in that way - showed that there was specialization to language in the left hemisphere and these specializations are related in some way to handedness - right handed individuals, language seemed predominantly to be controlled in the left hemisphere, but left handed people had some language control in the left hemisphere since we saw some aphasia in everyone - ambidextrous people are left handed people who have learned to adapt their right hand - in adults, right hemisphere damage – most patients showed few aphasic symptoms (language problems) and rarely leads to complete aphasia; individuals that did show aphasic symptoms, were always either left handed or ambidextrous - right handed individuals do not show aphasic symptoms when they have right hemisphere damage - if your right handed, language is in the left hemisphere; if your left handed, language is in both hemispheres – language loss will not be that severe for left handed in damage to either hemisphere - right hemisphere damage in left handed individuals show excellent recovery from aphasic problems (because have the other hemisphere as a back up) - in children (less than 5 years old), damage to either hemisphere has an equal probability of producing aphasic symptoms; thus, in children, language is involved in both hemispheres - thus, in adults it becomes lateralized, but not in children – developing brain is not fully lateralized - 100 % of children (less than 5) showed recovery of symptoms when had damage to either hemisphere - as you age, the brain does become more lateralized – around the age of 5, becomes more lateralized until get to adolescence, where brain is pretty much fully lateralized - lateralization occurs pretty much in right handed individuals, but not left handed - since there is greater lateralization and more plasticity in the brain, can remove one hemisphere, and the individual will do much better than if they didn’t remove it- better to remove it, since if leave it, will have scar tissue which can then cause epilepsy and disrupt the whole brain - a-collosal individuals: born without a corpus collosum - towns in Quebec have lots of families where they have genetic defect causing them to have corpus collosum, and studied them to see what happened during their development - these individuals have language on both sides of the brain - have also researched children that have had early extensive brain damage (one hemisphere is really damaged and didn’t remove it) – language will always be on the opposite side of the brain where the damage is - this tells us that the left hemisphere is better at language, and it actively suppresses the right hemisphere as the right handed individual matures; which is why we don’t see the suppression in the corpus collosum, because the left hemisphere cannot send the suppression signal to the right hemisphere - some research suggests that individuals that are left handed have had some small amount of brain damage early on in that it isn’t suppressing the right hemisphere Anatomical evidence behind left and right hemispheres: - in right handed individuals, in left temporal lobe, the plana temporale – primary language area in the temporal lobe, is larger, more convoluted and heavier by 1/3 compared to the plana temporale in the right hemisphere - could be due to a result of more usage – looked in other great apes, and found that this was also true in the great apes, and other animals that used vocalization as a form of communication (birds – much simpler brains, but still had language/bird song in the left hemisphere) - thus, it appears that left hemisphere use for language has a genetic component that has been seen in many different evolutionary lineages - newborns and left handed individuals, where no specialization, the left planal temporally is still larger, thus there is a genetic component that builds the left temporal lobe to be bigger and capable of language - in the 10 and 31 week of gestation in humans, already see an enlargement in the left planal temporally Research with sodium amital: - another approach that confirmed what we already know - if patient is up for surgery for epilepsy, we want to know where the epileptic focus is - usually is in the hippocampus; which is inside the temporal lobe, above the speech area - sodium amital is a sedative that they inject into the carotid artery - make them sit up and hold up arms; one day they will anesthetize the right hemisphere, and then the next day the left, and determine where the language area is - get them to count from 100 backwards - will see that the opposite side of the body will go limp, if they keep counting despite the decrease in motor response, then language is not on that side - also found that if your right handed, it
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