Lecture 31 Flashcards
Describe the role of association cortex interactions in
higher brain functions
the association cortex is responsible for associations within and across modalities
- example: linking the word dog. Involves language (temporal association cortex), vision (parietal cortex) + meaning (semantic memory).
Visual working memory involves coordination between DLPFC (motor association) and either posterior parietal
(spatial) or inferior temporal (identity) visual association areas
Language involves coordination between auditory association cortex (specifically Wernicke’s area which supports speech comprehension) and motor association cortex (specifically Broca’s area which supports speech production)
Describe what would happen with damage to the superior temporal gyrus of the dominant cerebral hemisphere (usually left)
Damage to Wernicke’s area which is responsible for comprehension and involved with auditory association
Leads to receptive aphasia
Describe what would happen with damage at the posterior inferior frontal gyrus of the dominant cerebral hemisphere (usually left)
Damge to Broca’s area which is responsible for speech production and involved with motor association area)
leads to expressive (non-fluent) aphasia
If an individual had a corpus collosotomy and you verbally asked them to raise their right arm, what would happen? What if you asked them to raise their left arm?
Corpus callosotomy severs the main connection between brain’s two hemispheres to reduce severe epilepsy
Person can raise their right arm because the left hemisphere controls the right side of the body and language processing is localized to the left hemisphere. So the left hemisphere receives and understands the command and can send motor signals to raise the right arm. Wernicke’s area and motor areas can communicate with one another.
Person cannot raise the left arm in response to a verbal command. Command is processed in left hemisphere but cannot be relayed to the right hemisphere, which controls the left arm.
Describe the interhemipsheric transfer experiment that involved visual problems presented to only one eye at at ime.
- In an animal with an intact corpus collosum and optic chiasm, when a visual problem is presented to only one eye, and then later shown to only the other eye, the animal can complete the visual problem because interocular transfer can occur due to intact optic chiasm and corpus callosum
In an animal with an intact corpus callosum but a split optic chiasm, the same result is found as information is still shared between hemispheres via the corpus callosum
However, if both optic chiasm and corpus collosum were split, the animal could not complete the visual problem with the other eye as no transfer will occur between hemispheres
If the corpus collosum was split and the optic chiasm remained, the animal will still fail the task. The learned info was stored in one hemisphere and the current task is being processed by the other
Describe the interhemipsheric transfer experiment that involved the subject selecting an object (manually and verbally)
When a subject with an intact corpus callosum has a familiar object flashed in their monocular field, they can select the same object that is hidden beneath a screen with either hand.
however, subjects that had undergone a corpus callostotomy were tested
- if the object was flashed in the left monocular field, they could only pick up the object with their left hand. the image is processed in the right visual cortex and the right visual cortex can communicate with the right motor cortex, which is responsible for descending commands to the left side of the body
- For the above same reasons, objects flashed to the right monocular field can only be picked up by the right hand.
If instead of picking up the object, the subject was asked to verbally identify the object seen in the picture, subjects could only do this when the object was shown in the right monocular field. This is because the image is processed in the left visual centre, which can communicate with the brocas area (lateralized to the left, language dominant hemisphere). If the image is presented to the left monocular field, without a CC, right visual centre can’t communicate with brocas area. Person might say they couldn’t see the object (confabulation), even if they could pick it up or draw it with their left hand.
Describe the deficits associated with posterior parietal lobe injuries (both to the dominant, non-dominant side and bilaterally)
Dominant (left) damage
- left/right confusino
- agraphaia (can’t write)
- acalculia (can’t calculate)
- anomia (can’t recall words)
Non-dominant (right) damage
- spatial problems
- neglecting parts of the body
- denial of any such deficiency
- Damage here often causes hemispatial neglect—where the person literally ignores one half of space, usually the left side (since the right parietal lobe attends to both visual fields, but especially the left). So will only draw clock numbers 1-6 maybe.
Bilateral damage
- Ocular apraxia (can’t control gaze)
- Inability to integrate components of a visual scene (can see the tree but not the forest)
- Optic ataxia (inability to accurately reach for an object
Differentiate between apperceptive agnosia and associative agnosia
Apperceptive agnosia involves inability to ‘represent’ objects
- you cannot copy letters or shapes (can’t assemble lines and edges into objects)
Associative agnosia associated with lesions further along the ventral stream
- You can copy letters or shapes but you can’t tell a person what they mean
- no issues with representation but cannot identify
both are a result of inferior temporal lobe injuries.
Both associative and apperceptive agnosia are associated with damage to the ventral visual stream, particularly involving the occipito-temporal regions,
However, apperceptive agnosia tends to result from posterior (more occipital) damage, while associative agnosia is linked to lesions further along the ventral stream which are more anterior
Explain blindsight
Destruction of V1 causes cortical blindness
No conscious vision but still have residual visuospatial abilities such as the ability to avoid an obstacle
Mediated by connections through the superior colliculus and thalamus (pulvinar nucleus) to posterior parietal dorsal stream areas
This is knows as blindsight, or cortical blindness, and is thought to be mediated by connections through the superior colliculus and thalamus (pulvinar nucleus) to posterior parietal dorsal stream areas (this pathway is still intact)
Person would exhibit confabulation though. Would make up a reason for why they could walk around an object. Generation of a false memory without intention to deceit
Fill in the blanks:
Using ____ to measure activation and communication in brain networks:
short-term and working memory tasks activate the _________, during maintenance of visuospatial information, ______ interacts mainly with the ________
If manipulation (rotation) is also required, ______ will interact with the _____
fMRI
dorsolateral prefrontal cortex
DLPFC
posterior parietal cortex
DLPFC
striatum
