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Brain lesions lol (Single vs double dissociations
--> doesn't tell…
Brain lesions lol
Single vs double dissociations
--> doesn't tell us function is localized in an area, merely that area is necessary for functioning
Single dissociation
--> Lesion A affects performance in Task A but not B
--> Lesion in B doesn't affect performance in either task !!
-------> we only learn that one lesion/region is involved in one function, and that another lesion isn't involved in any!!
Double dissociation
--> lesion A affects performance in task A but not B and lesion B affects performance in task B but not A!!
------> we learn that a lesion/region is involved in one function, but not in another function (Both lesions serve as each others control)
Split brain studies
--> hearing suppression (right ear superiority if presented different sound to both ears)
sodium amobarbital
---> to see where language center (broccas etc located)--> ansetazise one hemisphere, see if language is good
--> then anestazise the other one ---> double dissociation :D!!! #
No lesions bt abnormal behavior
--> double dissasociation
--> dyslexic children: able to read by soon dnot sight (dayseidetic dyslexia) vs those able to not read by sound but on sight (dysphonetic dyslexia)
---> double dissociation #
Normal people No lesion laterality studies
--> double dissociation
--> find two different hemispheric specialities
------> eg. left parietal = imagery while right parietal = spatial encoding------> or dichotic task: verbal material explode through touch = faster processed when right hand (left hemisphere / language center) than left hand used VS spatial information material = faster processed when left hand is used (cause right parietal lobe :) !! # #
TMS studies cause temporal lesion
---> each participant = his own control :D #
--->eg. left parietal for imagery task , right one for spatial
lesion assumptions:
damaged area = where function located
--> WRONG !! could just be a mediator / relay station
--> like wise healthy area could be impaired because relay statin = gone but theres no lesion there !!
temporal aspect
--> brain heals over time (neuroplasticity / reduced swelling caused by stroke / injury that might have affected areas around lesion)
--> bad temporal resolution
Some small (even big) lesions might not actually affect functioning / or affect functioning but in a non obvious way !
--> important when making composites to get a accurate lesion map of where it influences functioning (e.g. take all people with lesions in the area, that don't have deficits and overlay then onto of those with lesions in the same area that do ------> strongest overlap point = where lesion affects negative effects :P !!
Lesion Overlay maps VS lesion subtraction
---> Example Lesion on right hemisphere --> lead to visual field defect !
----> overlay all lesions who have visual field defect = might falsely think temporal junction lesion is responsible for the defect (cause stronger overlapping there)
---> take all the people with lesion on the right hemisphere that have visual field defect - all ppl with lesion right hemisphere that don't have visual field defect, ---> and you see that its actually because damage to occipital lobe and optical radiation !! :D!!
Lesion in area that causes issues for one person doesn't have to cause issue for other person even if in same area, because the function might be located somewhere else !!
--> brocca area / language is sometimes located in right hemisphere in 30% of left handers!!!)
assumes pure insertion !!
--> after lesion brain functions same was as before the lesion
-------> doesn't have to be because neuroplasticity and other areas take over :3!!
lesion vs fMRI
fMRi:
--> areas active could only be active because relay station as well !! #
--> only tells us about correlation!!!
--> T1 / T2 image not as good at actually detecting lesions/strokes (DTI or DWI is) <-- CT best for strokes cause blood = white
--> normalization is difficult cause less orientation points because of grey matter damage :p !!
Lesion
--> tells us about causation!!
---> cause whether or no lesion area = relay station or not IT IS NECESSARY TO FUNCTION (in case of impairment :3!!)
statistical analysis for lesions in fMRI
---> VAL, BrainVOX and VLSM = lesion is manually identified for each person and statistical maps are generated specifically around that area to make it more accurate and to overcome T1 and T2 image limitations (sometimes bad at detecting lesions :3 !!)
---> VAL = compare people who have lesion and impairment with ppl who have lesion in same area but no impairment + use fact that ppl with impairment usually have larger lesion size than those that don't! # #