lecture 6 - cerebral asymmetry Flashcards
left brain - folk psychology
analytical logical detail reading, writing, arithmetic, language intelligence dominant?
right brain - folk psychology
holistic intuitive whole picture artistic music emotional intelligence spare tire?
anatomical asymmetries
- weight and size?
temporal lobe asymmetry
- right larger and heavier than left
- planum temporale: larger in left
- Heschl’e gyrus: larger in right
slope of sylvian fissure
asymmetry
- gentler on left
hemisphere differences.
right = further anterior left = further posterior
split brain procedure
- commussurotomy
- surgical procedure of severing ther corpus callosum
- two hemispheres can’t communicate. - motor crossover at brainstem, not affected. sensory info to just one hemisphere.
neurologically intact vision
left visual field of each eye goes to right visual cortex.
both right visual field project to left visual vortex.
- left = language. seeing visual on right hemisphere - cross info over to left to name.
split brain patient vision
left visual field of each eye goes to right hemisphere.
info cant cross to left hemisphere to name.
2 conclusions from split brain patients
test on 2nd conclusion
- language processing is (usually) lateralized on left
- after tactile tests - maybe right hemisphere cant ID?
test #2 = ask about function of object. both functionally ID, right cant semantically name.
chimeric face
verbal description compared to left hand ID.
- strong left langugae usually = strong right face *
- name the face = rvf to LH. cant name in lvh.
- point w left hand = Lvf, RH - fusiform face area. LH, Right hand makes more errors.
WADA technique
- use?
- substance?
- process?
- surgery planning
- sodium amobarbital
inject thru carotid, ipsilateral brain anesthesia = contralateral paralysis. - speech output test. if language is on only on L -> wont speak when L is anesthetized.
bilateral presentation
unilateral presentation
perceptual asymmetries
- both sides = stimuli on both sides.
: face on LVF = more accurate than on RVF. language better on RVF(LH) than LVF(RH) - one side
perceptual asymmetry - different accuracy in perception at different places.
lateralized auditory
- stimuli from each ear goesto both sides of brain.
cochlear nucleus multiplies auditory. one copy to L olive, other copy to R olive. for both ears
dichotic listening presentation.
ipsilateral suppression,
contralateral dominance
two ears, different auditory info.
Ba in L ear, to RH.
Ga in R ear to LH.
Ga in LH so say Ga. then maybe say Ba bc ipsilateral works (less suppressed)
3 theories to perceptual asymmetriers?
- direct access theory
- callosal relay model
- activating-rienting model
direct access theory
perceptual asymmetry theory.
- input hemiphere processes info. performance varies
callosal relay model
perceptual asymmetry theory
- info transferred to best side, which degrades performance.
(left not processing face, has to send to RH via corpus callosum)
activating-orienting model
perceptual asymmetry
- attentional bias leads to information aliency
- priming /tuning to LVF for face. and RVF for words.
spatial frequency hypothesis
- spatial frequency =alternating btw light and dark. - distinguish btw things
- hemispheric laterality
in order to distinguish things that are very easy = low spatial frequency. right hemisphere advantage.
distinguish objects that look v similar = high spatial frequency. left hemisphere advantage.
=> right big picture
=> left more details
hemispheric differences in auditory processing of pitch
* ipsilateral suppression.
same pattern as vision.
lower tones = right hemisphere
higher tones = left hemisphere.
Is hemispheric difference in auditory/sensory absolute or relative phenomenon?
relative phenomenon.
same pattern in 2 different sound ranges = not consisten (above XHz, the dominance is not only one side) sensory system silters frequency information in rangein which they are experiencing.
split brain patients - modes of processing rely on different hemispheres
- chimeric stimuli
- hemispheric advantage
test set + match set. designed to be matched on appearance and function.
- match by appearance: see LVF (in RH), by function: see RVF (in LH)
- hemispheric advantage - work different ways in terms of context. LH - pick by function. RH - pick by appearance.
global vs local processing
-lesion patients - dunno where they are, but use this test to determine.
in both linguistic and non-linguistic tests.
RH lesion = see local processing (seeing detail) - LH in tact (bigpic)
LH lesion = big pic. RH working.
transfer of sensory information between hemispheres
- average adult.
- LVF vs RVF. ERP response in O1 vs O2.
flickering checkboard in LVF or RVF - push button, sometimes Lhand, other Rhand. collect ERP in response to visual stimulus.
O1- left, O2 = right.
- LVF -> RVF, peak in O2 before O1. time btw 2 peaks = time to cross CC.
-RVF -> LH. O1 first, O2 second.
inter-hemispheric interaction
-neurologically intact patients.
easy test - better or worse performance for contralateral same number?
difficult - better or worse performance for contralateral same number?
*why?
fixate on spot. 2 numbers above, 1 number below. say if number on bottom matches either of top ones.
both numbers on same side of visual field = better. when opposite sides of visual field - need to cross hemispheres = worse performance
-difficult: add numbers to get !0 or more.
-same visual field= worse performance
contralateral visual field- hemispheres’stalk = better performance
*maybe ned both hemispheres to calculate, so having VF on either sides facilitates the process.
