Lateralisation
- Created by: meg_lou
- Created on: 12-05-17 10:19
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- Lateralisation
- Lateralisation of function
- Corpos Callosum
- Separates left and right hemisphere
- Marc Dax
- Brain damaged patients with speech problems
- Non had damage only in the RH
- Language might be localised to one hemisphere of the brain
- Brain was thought to act as a whole in the 1800's
- Brain damaged patients with speech problems
- Tests
- Dichotic listening task
- Most people report more of the digits presented to right ear
- LH specialises in language
- Most people report more of the digits presented to right ear
- Sodium Amytal test
- Injected into the neck which anesthetizes one hemisphere of the brain
- Allows other hemisphere to be assessed
- Injected into the neck which anesthetizes one hemisphere of the brain
- Dichotic listening task
- LH
- Aphasia is a deficit in language due to brain damage in LH
- Broca's - loss of speech but could comprehend e.g. Tan
- Both aphasic patients had LH damage to prefrontal lobe
- This became known as Broca's area, associated with speech production
- Both aphasic patients had LH damage to prefrontal lobe
- Wernicke's - ability to speak but no comprehension
- Patient suffered a stroke and was able to speak but could not understand what was said to him
- Wernicke's area associated with speech comprehension
- He suggested that broca's and wernicke's area are connected (arcuate fasciculus)
- Wernicke's area associated with speech comprehension
- Patient suffered a stroke and was able to speak but could not understand what was said to him
- Language most lateralised of all abilities
- Broca's - loss of speech but could comprehend e.g. Tan
- Apraxia - bilateral difficulty performing movements when asked to do so
- Analytical memory processing - relation of parts that make whole
- Aphasia is a deficit in language due to brain damage in LH
- RH
- Able to understand single written/spoken words
- Better at tasks for spatial ability, emotional stimuli and musical tasks
- Holistic memory processing - parts or whole but not relation between
- Able to understand single written/spoken words
- Corpos Callosum
- The split brain
- Myers and Sperry
- Four groups of cats: corpos callosum severed, optic chiasm severed, both severed, controls
- Phase 1 - cats learned a level-press pattern discrimination task with a patch over one eye
- Phase 2 - the patch was switched to the other eye
- Group 3 acted if the task was new to them
- Found that the corpos callosum transfers learned information between hemispheres
- When cut, each hemisphere functions independently
- Humans
- First operations to sever corpos callosum performed on patients with severe epilepsy
- Reduce severity of convulsions by restricting epileptic charges to half the brain
- Tests of split brain patients
- Visual stimuli flashed to right or left of fixation point on screen
- Presented to LH - view/touch with right hand and name it
- Presented to RH - view/touch with left hand but could not name it
- LH involved with language!
- Cross-cuing
- Red or green light flashed to LVF
- Patient improved gradually, suggesting that the colour information was being transferred over neural pathways
- Not true - patient would shake their head if they made a wrong guess
- RH heard incorrect guess and signalled it was wrong by shaking of the head
- Cued the LH to correct itself
- RH heard incorrect guess and signalled it was wrong by shaking of the head
- Not true - patient would shake their head if they made a wrong guess
- Patient improved gradually, suggesting that the colour information was being transferred over neural pathways
- Red or green light flashed to LVF
- Visual stimuli flashed to right or left of fixation point on screen
- Learning 2 things at once
- Pencil in LVF and orange in RVF
- Patient grasped both object and said there were 2 oranges
- LH then saw it was a pencil and a orange
- Patient grasped both object and said there were 2 oranges
- Helping hand phenomenon
- Pencil in LVF and orange in RVF
- Right hand reaches to pick the orange under direction of LH
- Left hand would grab the right hand and direct it to the pencil
- Right hand reaches to pick the orange under direction of LH
- Pencil in LVF and orange in RVF
- Pencil in LVF and orange in RVF
- First operations to sever corpos callosum performed on patients with severe epilepsy
- Myers and Sperry
- Cerebral asymmetry
- Analytic-synthetic theory
- Different modes of thinking, analytic (LH) and synthetic (RH)
- LH - logical and analyses stimulus information
- RH - makes overall judgements but cannot quantify it
- Became segregated through evolution
- Difficult to test empirically as it is not possible to specify degree of analytic or synthetic processing
- Different modes of thinking, analytic (LH) and synthetic (RH)
- Motor theory
- LH specialised for fine motor movement e.g. speech
- LH lesions disrupt facial movements more than RH lesions
- Degree of disruption of nonverbal face movements is positively correlated with degree of aphasia
- Consistent with mirror neuron theory
- Doesn't say why motor function became lateralised
- Linguistic theory
- Primary role of LH is language
- Based on studies of deaf people using ASL with unilateral brain damage
- WL had difficulty signing and understanding others signs
- Was able to produce and understand other gestures - aphasia not a result of motor or sensory deficits
- WL had difficulty signing and understanding others signs
- Based on studies of deaf people using ASL with unilateral brain damage
- Other theories see it as a secondary function
- Primary role of LH is language
- Analytic-synthetic theory
- Lateralisation of function
- Survival advantages of lateralisation
- The 5 classes of vertebrates all have lateralised brains
- Efficient to locate similar neurons next to each other
- Two different kinds of tasks might be easier to perform
- Language is highly specialised and unique to humans
- Other primates also communicate by sounds with specific meanings
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