Lecture 31 Flashcards
(30 cards)
What are the association cortexes function
- many higher functions are task specific interaction involving specialized association cortex areas
- they are involved in associating within and across modalities (e.g. linking the word dog with visual and semantic information)
What is visual working memory?
- visual working memory is the ability to temporarily store and manipulate visual information
- it involves coordination between dorsolateral PFC (motor association) and either posterior parietal (spatial - where things are) or inferior temporal (identity - what things are) visual association areas
what does association cortex receptive field refer to?
- it refers to the idea that we don’t have individual neurons for individual people, but rather categories and networks
- this if opposite to monkeys who have specific neurons to specific visual information (e.g. bananas)
Whats the difference between unimodal and multimodal/polymodal?
- unimodal processes input from one sense (e.g. auditory)
- multimodel and polymodal processes input from multiple senses (e.g. auditory and visual)
what is complex cognition?
- task-specific interactions between receptive fields of neurons/column involving association areas
- with complex cognition you can attend to a complex stimuli, identify relevant features of such stimuli, plan responses and store information
Language involves coordination between which to areas?
- Brocas (speech production and motor association) and Wernickes (speech comprehension, and auditory association)
What is Wernickes area involves in and what happens when it is damaged?
- It is involved in speech comprehension and auditory association
- if it is damages, patient will have receptive (fluent) aphasia where they can’t comprehend speech
What is Broca’s area involves in and what happens when it is damaged?
- it is involved in speech production and motor association
- if damaged, patient will have expressive (non-fluent) aphasia, where they can’t produce speech
What are the cognitive function that are localized to the left hemisphere
- Speech and comprehension
- mathematical ability
- right visual field
______ is assigned to the hemispheres in which language resides in
cerebral dominance
Why can an individual with a severed corpus callosum raise their right arm when given a verbal command, but not their left arm?
- this is because the left hemisphere is responsible for both language comprehension and controlling the right side of the body
- however the left arm is controlled by the right hemisphere which can’t directly understand verbal command because this is controlled by the left and hemisphere and since the corpus collosum is severed the right hemisphere may not receive the message to act.
What is one way that an individual can lift they left arm even if the corpus callosum is severed?
- if the command is delivered through visual or non-verbal cues
give an example of an experiment that shows the importance of the corpus callosum for interhemispheric transfer
- With the left eye closed, animal learns a visual discrimination task
- the information is transmitted to both hemispheres through connections made by optic chiasm or corpus callosum, so when the animal was tested with its right eyed closed, the task can still be performed because both hemispheres have learned the task
- this result is the same if the optic chiasm was severed before the animal was trained because information is transformed through the corpus callosum
- however if optic chiasm and corpus callosum is severed, the information is not transferred and each hemisphere must learn the task independently
What is interhemispheric transfer
- the two cerebral hemispheres can function somewhat independently, as in control of one hand
- however, information must be transferred between both hemispheres to coordinate activity on the two sides of the body
Describe an experimental set up in human patients who have undergone surgical transection of the CC? And discuss the results.
- the purpose was to prevent interhemispheric spread of epilepsy
- CC is severed, but optic chiasm is intact so the visual information is directed to one hemisphere by the patients fixing vision on the central point of the screen
- a picture is flashed on one side of the fixation point, so that visual information reaches only the contralateral hemisphere
- there opening beneath the screen that allows the patient to manipulate objects that could not be seen
- normal individuals were able to locate the object with either hand
- patients with transected CC, could only locate the correct object only with the ipsilateral (same side) to the project image (contralateral to the hemisphere that received the visual information)
- this is because with the CC cut the visual and motor ares are interconnected only on the same side of the brain
If the same experiment was conducted, but patients had to verbally identify the object how would the results differ
- if the object was presented on the right of the fixation point, the patient would make a correct verbal response because the visual information only reached the left hemisphere (language dominant)
- however, patient would not be able to verbally identify a picture presented on the left of the fixation point because visual information only reached the right hemisphere
What is the function of the posterior parietal lobe
- visuospatial abilities, determining the position in space
What is the function of the hippocampus and damage to this area causes…
- learning and memory
- damage to this area can affect long or short term memory
What is the function of the frontal lobe and damage to this area causes…
- motor planning and initiating movements
- damage to this area results in disinhibition to behaviour and personality change (Phineas Gage), disexecutive syndrome (Penfields sister)
What are the two different agnosia’s that result from
injury to inferior temporal lobe (ventral stream)
- apperceptive agnosia involves the inability to represent objects (e.g. draw or copy object accurately –> proximal lesion
- associate agnosia can represent but not identify (e.g draw the object but not know what it is) –> further along the ventral stream
What is the result when the posterior parietal lobe is injured (dorsal stream?
- damage to the posterior parietal cortex results in the inability to attend to or represent contralateral visual field
- when asked to copy a drawing patient ignore the visual field contralateral to their lesion, this is known as hemineglect
What are the effects of damage to the dominant (left) hemisphere
- left/right confusion
- agraphia (can’t write)
- acalculia (can’t calculate)
- anomia (can’t remember words)
What are the effects of damage to the non-dominant (right) hemisphere
- spatial problems
- denial any such deficits
- neglecting parts of the body
what are the of bilateral damage to the brain
- ocular apraxia (cant control gaze)
- inability to integrate components of visual scene
- ocular ataxia (inability to accurately reach for an object)
