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
