Lateralization and Language (Lecture 8) Flashcards
cerebral cortex (neo-cortex)
6 layers of cells, gray matter and white matter, convoluted surface increases surface area, specialized for memory, attention, perceptual awareness, thought, language, and consciousness
sulcus (sulci)
grooves in cerebral cortex
big sulci
fissures in cerebral cortex
gyrus (gyri)
bumps in cerebral cortex
cerebral cortex connected by:
the cerebral commisures (anterior commisure and corpus callosum)
anterior commisure
1/10 the size of the corpus callosum
corpus callosum
200 million axons
right hemisphere is slightly _____ and ______ than the left hemisphere
right hemisphere is slightly larger and heavier than the left
left hemisphere contains more:___
gray matter
right hemisphere extends ______ posteriorly
farther
temporal lobes display a _______
marked structural asymmetry
are neurotransmitters distributed symmetrically or asymmetrically?
asymmetric
Marc Dax
had over 40 patients with speech problems all with left hemisphere damage
Pierre-Paul Broca
2 aphasic patients with left hemisphere damage “Tan”, lesions to prefrontal cortex=Broca’s area
aphasia
deficient in the ability to produce or comprehend language
Hugo-Karl Liepmann
apraxia almost always associated with left hemisphere damage
apraxia
difficulty in performing movements when asked to
laterality
the idea that the two cerebral hemispheres have separate functions
unilateral lesions
traumatic brain injury, surgical removal, stroke
*unless done surgically, lesion does NOT occur within distinct boundaries of single structures
stroke=
an interruption in blood supply to any part of the brain, it may lead to sufficient loss of oxygen to cause tissue death
sodium amytal test
given before neurosurgery in an effort to avoid damaging areas of cortex importance for speech and language
sodium amytal test steps
sodium amytal injected into carotid artery, brief (10min) inactivation of ipsilateral hemisphere, loss of function f contralateral arm and visual input from contralateral visual field
dichotic listening test
based on the idea that although each ear has projections to each hemisphere auditory cortex, crossed pathways are more numerous and faster conducting
dichotic listening test steps
subjects are played two different series of 3 words simultaneously (one series to each ear), then asked to recall as many of the six words as they could
in the dichotic listening test, patients could recall more words presented to their _____ hemisphere (______ ear)
left hemisphere, right ear
when the same dichotic listening test was done with melodies instead of words, patients could better recall melodies presented to their _____ hemisphere (___ ear)
right hemisphere, left ear
functional brain imaging
subjects are asked to perform some task (e.g. read, listen to a story) while brain function is measured by fMRI or PET
typically, _____ hemisphere more active during verbal tasks (i.e. speaking, reading, or hearing words)
left
electrical stimulation
stimulation to either hemisphere produces twitches, dysesthesias, light flashes, buzzing sensations
stimulation to right temporal lobe=
more deja vu, fear, dream state, episodic memory recall
simulation to left frontal lobe, parietal, and temporal cortex:
disrupts speech
stimulation to right temporoparietal cortex disrupts:
judgement of line orientation, facial expressions, short term memory for faces
the split brain
ground-breaking work on the function of the corpus callosum, found through the study that the cat brain had the capacity to act as two separate brains (when corpus callosum and optic chiasm are severed)
conclusions of the split brain experiment:
corpus callosum transfers learned info from one hemisphere to the other, and hemispheres can operate independently
language is the ___ ______ of all cognitive abilities
most lateralized
right hemisphere is capable of understanding
simple spoken and written words and sentences
tachistoscope
visual information presented to each visual field while patient stares at center “fixation cross”
most subjects accurately identify objects explored with their ____ hand. (most braille readers read more rapidly with their ____ hand)
left hand
left hemisphere damage=
apraxia
more activation in ___ hemisphere versus ____ hemisphere during ipsilateral hand movement
more activation in left versus right
right hemisphere is better at:
spatial tasks like putting together puzzles with blocks
emotion = _________ hemisphere
right (emotional content of readings’, expression of emotions, identifying facial expressions
subjects that felt 3D objects with _____ hand were more accurate in identifying 2D test stimulus that best represented what they felt if it were made of cardboard and unfolded
left
Broca’s area=
left inferior frontal
Wernicke’s area=
left planum temporale
large anterior lesions most likely to produce:
expressive symptoms
large posterior lesions most likely to produce:
receptive symptoms
3 evolutionary theories on why we have cerebral asymmetry of function:
analytic-synthetic theory
motor theory
linguistic theory
analytic-synthetic theory
two modes of thinking (analytic (left) and synthetic (right), vague and essentially untestable
motor theory
left controls fine movements-speech is just a category of fine movement, left damage may produce speech and motor deficits
linguistic theory
left hemisphere is specialized for language, deaf people with left hemisphere damage show deficits when signing but not mimicking
commissurotomy limits:
convulsive activity (may never have another major convulsion)
when you present a picture (ring) to the right visual field (left hemisphere) of a split brain patient:
left hemisphere can talk and say ring
right hand can show you, left hand can’t
when you present a picture (key) to the left visual field (right hemisphere) of a split brain patient:
right hemisphere can’t talk and subject will report that they do not know what it was
left hand can show you what it was, right hand can’t
helping- hand phenomenon
presented with two different visual stimuli, the hand that “knows” may correct the other
chimeric figures task
only symmetrical version of right half of faces recognized (indicates competition between hemispheres)
chimeric figures test and completion
the left hemisphere of a split-brain patient sees a single normal face that is a completed version of the half face on the right. at the same time, the right hemisphere sees a single normal face on the left
