cerebral asymmetry Flashcards
lateralization
two hemispheres having separate functions, split in two independent halves
left hemispheres function
verbal, complex information
right hemispheres function
nonverbal, emotion, spatial
laterality is relative or absolute
relative, both hemispheres are involved in almost all behaviours, some are just more specialized in one hemisphere over the other
what factors influence how lateralized a skill is
environmental and genetic
which hemisphere is larger and heavier
the right
anatomical differences between right and left hemi
- left has larger planum temporale (Wernicke’s area), thalamus, secondary auditory cortex, hemi goes further forward
- right has larger primary auditory cortex (2 Heschl’s gyri), sylvian fissure is angled up more, hemi goes further back
neuronal assymetry
- more complex dendritic branching in the left hemisphere because it’s verbal
- neurotransmitters are different across hemispheres
what kind of differences might cause the anatomical and neuronal differences in the brain
genetic
Broca’s Area
speech production
- near (in front of) the motor cortex
- know what you want to say but difficulty saying it
Wernicke’s area
secondary auditory cortex
- speech comprehension
- say real words fluently but make no sense
what was early treatment for epilepsy and what did you have to do first
surgical removal of the cortex the seizures originate from, must brain map first to find important areas like speech and motor control to avoid damaging them using electrical stimulation
what did early brain mapping find
some functions are symmetrical and some are not
- left frontal and temporal lobe can produce speech when weakly stimulated
- functions can be blocked with strong stimulation
- right hemisphere is more perceptual functioning
double dissociation
brain area A does function A, brain area B does function B
If area A is damaged it does not affect function B
after TBI person has difficulty reading but not writing, another person has difficulty writing but not reading
removal of the left lobe results in
lower memory quotient and verbal recall
removal of the right lobe results in
nonverbal recall, performance IQ, copying drawings
commissurotomy
severing of the corpus callosum to avoid spread of seizure activity between hemispheres
for grand mal seizures
corpus callosum
bundle of 200 million nerves, white matter, that connects the two hemispheres so they can communicate with each other
result of a commissurotomy
no obvious changes, reduced seizure activity.
however, compensatory behaviours to make up for deficits, split brain patients
how can split brain patients still have a functioning contralateral fov
the optic chiasm is not severed, just corpus callosum
what happens if a split brain patient is asked what is in their left fov
they will say they see nothing
what happens if a split brain patient is asked what they see in their right fov
they can name and describe what they see
what happens if you ask a split brain patient to grab the far left object
they will grab the correct object
what happens if you ask a patient to pick a face after showing them chimeric image
they would pick the one on the left
are split brain patients aware of the discordance
no
what are the statistics for left hemi verbal dominance in handedness
98% of right handers, 70% of non right-handers
- 15% are both hemi and 15% are right hemi
when asked to select an image, what will each hand do
choose the correct one, but left hand will make up a reason why
is lateralization a type of localization
yes
the right ear is better for what
language stimuli memories
- linguistic stuff, talking
the right hemisphere is better for what auditorally
melodic memories
- musical stuff
the left hemisphere is better for what auditorally
language, linguistics, tone,
the left ear is better for what
musical stuff, melody memory
when only one ear is used what type of pathway is used
monaural
an ipsilateral, both hemispheres will receive the information
when both ears are presented with different sounds what pathway is used
diaural
contralateral, you get the right sound on the left hemi and vice versa, ipsilateral is suppressed
which hand is better for braille
the left hand (right brain) because the right hemi is better at recognizing patterns
if you inject sodium amobarbital into the left carotid artery what side of brain and body will it affect
the left hemisphere, and the right side of your body
disconnection syndrome example
severing the connection between broca and wernicke’s area, resulting in lack of communication between the two resulting in an aphasia
apraxia
loss of fine motor skill due to damage in left hemisphere motor regions
what side of the mouth starts moving first when you talk and why
right side, because left hemi is verbal
which side of the face shows emotion more strongly and why
the left side because you rright hemisphere is emotion dominant
specialization theory
different hemispheres have different unique functions
interaction theory
one hemisphere might be better at a task but they cooperate with each other, both work on processing different parts at the same time
in 75% of fetuses, how early does hand preference show up
10 weeks
