HISTORICAL OVERVIEW early awareness came from observations during periods of war
IN ADULTS (over 20)
o Left Hemisphere wounds
100% of patients shows some aphasic symptoms (problems in speech and language)
Approximately 30% showed recover either left-handed or ambidextrous (both hands
Right handed people had more problems with left hemisphere damage didn’t recover
If you are left handed you can lose language but gain it back right hemisphere is
also capable of language in left handed
o Right hemisphere wounds
Most patients showed few aphasic symptoms, few language problems and rarely leads
to complete aphasia
Those who did language problems were always either left handed or ambidextrous
Right handed people did not have language problems
So for right handed people, language problem was an issue only if they had lesions in
If you are left handed, you lose language either way but it is not that severe
Recovery: they show very good recovery suggesting left-handed people have higher
IN CHILDREN (under 5)
o Damage to either hemisphere has an equal probability of producing aphasic symptoms
o Therefore there was some language on both sides in little children, unlike an adult.
o When you look at recovery, 100% of children who suffer brain damage show recovery
o Therefore the developing brain is not yet fully lateralized.
o Somewhere around the age of 5 or so, the brain starts becoming more lateralized.
o Lateralization occurs typically in right handed individuals and less in left handed
o Because there is less lateralization and its plasticity, if you remove half of the brain of a child,
they can still recover, not perfect but recover.
o Almost always on opposite side of the brain of the damage
o For some reason, the left hemisphere is better at language an suppresses the right
hemisphere, as they grow up.
ACALLOSSOL: born without a corpus callosum
o In adults, they have language in both sides and even as left handed
o Because the left and right cannot communicate, the left cannot suppress the right hemisphere,
it continues with language; only loses language if it has a connection with the left hemisphere.
ANATOMICAL RESEARCH What makes left hemisphere superior
Planum temporale primary language area in the temporal lobe
In the left hemisphere, the planum temporale is larger and more convoluted and heavier than the
exact same area in the right 1/3 larger left hemisphere is superior
What came first? Is it the cause or the effect
They looked at other greater apes and found that it was also found that the planum temporale was
larger suggests there is a genetic component
Newborns and left handed the planum temporale is still larger, without the experience so
basically it is the cause and not the effect. If you are right handed then language is almost always in the left hemisphere and for left handed, it is
Result of an experiment
o In right-handed individuals, info presented to the left hemisphere (has language) is faster and
the person responds more quickly if the info is presented to the verbal hemisphere
o It longer longer when it was presented to the non verbal hemisphere right hemisphere in
right handed people longer than the time i