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Ted Petit (310)

PSYB65 - Lec 9 (near verbatim).doc

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Ted Petit

Lec 9: Were finished with pharmacological part of human brain and behavior Classic neuropsychology; look at what each portion of the brain does General lateralization, how the diff sides of the brain are diff; how left hemi is diff from the right hemi; in many cases theyre the same, but there are differences particularly when it comes to language Lateralization of the brain = how the 2 sides of the brain arent exactly the same Historical perspective on lateralization of the brain: o How did we first begin to understand that the two sides of the human brain dont do exactly the same thing? o 1) During WWII: found patients who recovered from wounds, that they had problems but they werent the same problems; a lot of the behavioural problems (for ex: damage to right side of brain had beh problems in left part of body) were clear; then started noticing differences in problems with language between patients with damage to right hemi or left hemi start with adult research: damage to the left hemi in adults: 100% of patients will show some aphasic (used quite loosely) symptoms = some problem in language; approximately 30% = showed some recovery = the patients that showed recovery were either left-handed or ambidextrous; ambidextrous ppl tend to clump in with LH ppl; it appears that ambidextrous ppl are actually LH but have forced themselves to learn to do thing with the RH also; least amount of recovery = always in RH ppl language = in left hemi because 100% with damage in left hemi = language problems; handedness seems to affect where your language is and how important the left hemi is; if you are LHed, if you have problems, you tend to recover from them damage to the right hemi in adults: few language problems and it rarely leads to complete aphasia; the only ppl who did show any signs of aphasia with right hemi damage were either left-handed or ambidextrous AND they showed good recovery from their language problems; right handed ppl w/ right hemi damage did not show language problems in right-handed individuals, the language is in the left hemi; however, if youre left-handed, you have some language in both hemispheres language is bilaterally located; if youre right- handed and you damage your left hemi = you lose language but if you damage your right hemi, you dont lose language, so all of your language is in the left; if youre left-handed and you damage your left hemi OR right hemi, you lose language = you lose language from either side which means language is located on both sides if youre left-handed which means you can recover from damage from either side o Language in kids = how language develops o With children under age 5, when brain is still pretty much developing; walk at 1, talk at 2 (rudimentary language) o By 5 years of age, theyve been talking for around 3 years o During this early period (b4 age 5), damage to either side has equal probability of producing aphasic symptoms language is located on both sides in little kids (like left-handed ppl) o In addition, like left-handed ppl, 100% of children will show good recovery (maybe not perfect recovery) o Language on both sides, if theres damage on one side, the other side is capable of taking over o While the adult brain is specialized (hard-wired) because language is on left-side in right-handed ppl, in children, this isnt yet the case theyre developing and language is on both sides, even in right-handed kids, language is still on both sides o DEVELOPMENTAL PHENOMENOM: WHERE ALL CHILDREN HAVE LANGUAGE ON BOTH SIDES (plastic) o Then slowly, as you get older, language shifts from being on both sides of the brain, to being ONLY on left side of the brain in right handed patients (becomes concrete) o Developing brain = extremely plastic, can recover, capable of growth of dendrites/axons, pathways that go towards diff directions; if you remove a certain input into cortex of any animal, the vacated sites are taken over (axons will grow in from other regions) and form hypersensitivity to other capabilities (ex: someone who is blind, is especially talented muscician) o Certain languages are graphic, others are phonetic (more processed like Western language) brain processes language in diff ways depending on structure of language Acallosal: o born without corpus callosum o 2 hemis not connected o seems to be genetic, appears in small communities o have language on both sides of their brains as adults whether youre right handed or left handed doesnt matter; Kids with early extensive brain damage: o sometimes children have strokes or at birth they have extreme damage form scar tissue, probability of causing seizures/epilepsy if possible, better to go in and remove the damaged tissue; sometimes they may remove a whole lobe/portions of it because its known that in young ppl, the other side can take over the functions anywayo any type of severe damage in kids in whatever hemisphere it is in, their language is always located in the OPPOSITE SIDE OF THE BRAIN; doesnt matter which hemisphere was damaged, language will always be in the opposite hemi o usually recover well, and develop speech (may have subtle problems) What does all this mean? o Kids: seems that they have language on BOTH sides; if one side is damaged, language always winds up on the other side o Adults: in right-handers, left hemi becomes dominant for language, unless you are born without corpus callosum; if acallosal, language continues on both sides o Theory: you are born with both sides of your brain capable of language b/c both sides are working in kids. But it appears that left hemi (at least in right-handed ppl) is dominant for language (better-equipped for language). Slowly over time, left hemi becomes dominant and it seems to suppress the right hemi from being involved in language. o If you damage either hemi in a child, the other hemi can always take over; or if acallosal, left hemi cant suppress language in right, so language continues in both hemispheres o clearly, left hemi is better at language and in all ppl it is in the left and the vast majority of ppl show language ONLY in the left o left actively suppresses right hemi in terms of language as we mature Why is the left hemi
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