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Lecture 9

Lecture 9 - Cerebral dominance and the neuropsychology of language

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Department
Psychology
Course Code
PSYB65H3
Professor
Ted Petit

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Lecture 9 Chapter 4 and 15 (Laterality and Neuropsychological Assessment)
Cerebral dominance and the neuropsychology of language
Brain lateralization: the functions of the left and right hemispheres of the brain arent the
same. Left involved in language.
What do the right and left brains do? And why is it that we have different functions on
either side?
History: brain damage resulting from wars was recorded
Brain damage was different in different patients why was this so?
This was all only looked at in adults (no kids at war)
First real grasp of brain lateralization came from here
What they found was whenever the brain damage was in the LEFT HEMISPHERE,
when they studied these recovering patients 100% of the time showed some
APHASIC symptoms speech deficits
Aphasia: approximately 30% of these patients show some degree of recovery; 1/3rd
showed recovery (some didnt show recovery at all) and they were either left handed
or ambidextrous that showed recovery
Astute connection made that they were all left handed
Noticed a correlation between people left-handed/ambidextrous people that would
recover the only ones that could recover
We group ambidextrous people with left-handed people for the most part and they
are studied together basically ambidextrous people were genuine lefties that were
forced to use their right
Least amount of recovery was in right-handed individuals left hemisphere damage
= right hemisphere unable to recover
Since 100% of patients with damage to the left hemisphere showed some type of
deficit in speech aphasia it was distinguished that the LH of the brain is
responsible for language
www.notesolution.com
What about patients where bullet went into the right hemisphere
Showed very few language problems and relatively rarely did it lead to aphasia
The small % that did show aphasic symptoms were all left-handed or ambidextrous
(The small % that did show aphasic symptoms when the bullet when into the right
side of the brain were all left-handed or I was going to say bisexual or
ambidextrous, probably both. Anyway haha.”)
Furthermore, most of the patients showed recovery from the language problems
much greater than 30% that would recover with damage to the left hemisphere
Right-handed people with RH damage = NO APHASIC SYMPTOMS this
suggested language is located in the LEFT hemisphere (if you were right handed)
Then on a left-handed person, language is depicted bilaterally in the brain because
on a left-handed person, they show language problems if there is damage to either
side this means damage to either side can cause impairment in speech but there is
an advantage in that recovery is high because if one side is damaged, the other side
still has functioning for language and brain can compensate and you can learn how
to manage
Brain damage in children less than 5 years old
They have strokes and its not uncommon anoxia sometimes at birth itself
Damage to either side has equal probability of inducing aphasic symptoms, which
tells us that some language is found on both sides of an infants brain
However, 100% of kids will show some degree of recovery because either side can
take over the function if there is damage
Language is not lateralized brains of young children are much like that of left
handed or ambidextrous people
It appears that overtime during development, language slowly becomes lateralized to
one side; for right-handed people, left hemisphere gains ability to deal with language
Neuroplasticity: we know the brain is very plastic as a child and then becomes less
plastic as we grow up (advantageous so as to be able to store memories efficiently)
but it is very advantageous if you have brain damage as a child you can just totally
remove the damaged hemisphere and it will just be taken over by the other
www.notesolution.com
hemisphere
Acallosal patients
People born without a corpus callosum the fiber pathway connecting the left and
right hemispheres
Acallosal patients have language localized on BOTH sides of the brain in an adult
What does this mean?!: were born with both hemispheres each capable of language
acquisition and as we mature the left hemisphere is somehow seems to be dominant
for language in individuals
Even though we start with both hemispheres the power shifts from being all over the
brain, to being just onto the left hemisphere
If a person shows damage to the left hemisphere or if the hemispheres are not
connected it is the left hemisphere during development that actively supresses the
right hemisphere
Why do we say that? Because in individuals without corpus callosums, where the two
hemispheres cannot communicate, some functionality remains on the right hand
side through development into an adult brain
When they are connected, all the language moves to the left side; the left side seems
better at it and will tell the right side I will take over language, Im better at it.
Or if the left side is damaged, it cant supress the right hand side and therefore the
right hand side will not be supressed and some functionality can remain (Does this
mean you can only have function in your right hemisphere if you have damage to the
left at a young age? Because that is before it is set in and wouldnt have been
supressed by the left side yet)
This suppression is not as strong in left-handed people; there is still language
functionality coming from the right hemisphere
Why does this happen? Why specific to the left hemisphere?
Looked at the left temporal lobe at the planum temporale which is a primary
language area on the left hemisphere, this is more convoluted, heavier and larger
by about 1/3rd bigger, suggesting that the left hemisphere speech area is
www.notesolution.com

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Description
Lecture 9 Chapter 4 and 15 (Laterality and Neuropsychological Assessment) Cerebral dominance and the neuropsychology of language Brain lateralization: the functions of the left and right hemispheres of the brain arent the same. Left involved in language. What do the right and left brains do? And why is it that we have different functions on either side? History: brain damage resulting from wars was recorded Brain damage was different in different patients why was this so? This was all only looked at in adults (no kids at war) First real grasp of brain lateralization came from here What they found was whenever the brain damage was in the LEFT HEMISPHERE, when they studied these recovering patients 100% of the time showed some APHASIC symptoms speech deficits Aphasia: approximately 30% of these patients show some degree of recovery; 13 rd showed recovery (some didnt show recovery at all) and they were either left handed or ambidextrous that showed recovery Astute connection made that they were all left handed Noticed a correlation between people left-handedambidextrous people that would recover the only ones that could recover We group ambidextrous people with left-handed people for the most part and they are studied together basically ambidextrous people were genuine lefties that were forced to use their right Least amount of recovery was in right-handed individuals left hemisphere damage = right hemisphere unable to recover Since 100% of patients with damage to the left hemisphere showed some type of deficit in speech aphasia it was distinguished that the LH of the brain is responsible for language www.notesolution.com
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