Human brain lectures 14-22 Flashcards
Patient Mr. M
Patient Mr. M
Had semantic dementia: neurodegenerative disease that is characterized by deterioration of semantic memory
Sees sheep, but cannot name it and doesn’t know what they are.
Frontotemporal lobar degeneration – Can see that the sulci of the brain is much wider = neurons had died
Semantic Dementia Case Studies
Semantic selectivity for living/non-living things. Loses their ability to know about, for example, animals or things in the world. Episodic memory intact.
Can ONLY GENERALIZE – In drawings, they become very generic forms
Anatomical differences between left and right hemispheres
The sylvian fissure is about 12% longer (divides the temporal lobe and parietal lobes in posterior region) on left side than the right sylvian fissure. LEFT BRAIN GENERALLY LARGER
Cerebral petalias (the torque of the brain)
It’s pushed over a little to accommodate the larger temporal lobe of the left brain. A LEFT occipital, right frontal torque emerged during bipedalism. Lengthening symmetry of the left suggests that anatomical differences may have led to the to development of language.
Psychological studies of hemisphere differences: Tachistoscopic visual field studies
Remember! Visual field is opposite to the hemisphere.
RVF advantage for words
LVF advantage for faces, gaze directions
LVF global, RVF local.
Psychological studies of hemisphere differences: dichotic listening
RIGHT ear advantage for words
LEFT ear advantage for melodies (left ear goes to right hemisphere)
Psychological studies of hemisphere differences: Gaze direction in VF study
Left visual field projects to the right hemisphere.
Right visual field reports to the left hemisphere.
Study reports what the right hemisphere sees.
If the left eye is straight, it is projecting to the right hemisphere.
Global vs. local hemispheres are…
GLOBAL processing in the right hemisphere, LOCAl in the left hemisphere
The amytal (or wada) test
- The Wada test – ultimately puts one hemisphere to sleep for a period of time. Useful during surgery, avoid areas that control language – helps to know what hemisphere speech resides in an individual!!
- The carotid arteries provide the perfusions of the speech area of the brain in the left. If you inject the right carotid artery, it anesthesizes the right part of the brain. Vice versa.
- Left common carotid is injected. Left hemisphere is asleep, subject is given a spoon – but denies anything was given to them. Left hemisphere was asleep while a spoon was given to the left hand. Individual couldn’t speak at all when left hem was interfered.
The right hemisphere enables the patient to point to the picture of the spoon. Right hemisphere knows what was seen, not the left hemisphere. Right hem doesn’t have much control over language – the only thing it can do is point at a picture.
How can the corpus callosum be useful in surgery?
A cut corpus callosum can’t send seizure signals from one side of the brain to the other. Seizures still occur on the side of the brain where they start. After surgery, these seizures tend to be less severe because they only affect half of the brain.
Hemisphere control of expression
Subcortical - spontaneous
Left cortical - intentional
Voluntary expressions originate in the left hemisphere. Damage to the right hemisphere means you can initiate a “social” smile, but only one side of the face will show it.
Posner cueing task
Tests VOLUNTARY covert shifts of attention.
SELECTIVE ATTENTION has benefits and costs: There is a cost to directing your attention to the wrong place. Benefit if you use the cue and it points to the right side. If the arrow is wrong and the target is on the other side (invalid trials) = shifting attention covertly to the wrong location means you are slower than if you never attended to the cue at all.
What is the main trend of receptive field size across the visual system?
it gets larger from occipital to the temporal lobe! Moving along the “what pathway” the ventral stream….it gets bigger.
Lesions in what area of the brain affects ATTENTION?
Lesions in the RIGHT temporal parietal junction
–> This area is engaged in allowing you to shift attention. Once a lesion occurs, you have difficulty transitioning/moving attention from one area to another.
ERP vs. fMRI
fMRI does not provide good temporal resolution (WHEN a signal occurs), but has good anatomical resolution (WHERE it occurred).
ERPs do not provide good anatomical resolution, but have good spatial resolution.
ERPs have been measured in the Hillyard and Posner Cueing Tasks.
