Localisation and Lateralisation Flashcards
(23 cards)
What is localisation of function?
The idea that certain functions (e.g. language, memory etc) have certain locations within the brain.
Describe the case of Phineas Gage
- Phineas gage was working on a rail line in 1848. During an accident a piece of iron went through his skull
- The iron damaged his frontal lobes
- He survived the accident but experienced a personality change such as anger, loss of inhibition and emotional instability
Why is the case of Phineas Gage helpful?
It provides support for localisation of brain function because the area that the iron bar went through was responsible for personality.
What are the 4 key areas of the brain for localisation?
Motor Area
Somatosensory Area
Visual Area
Auditory Area
Describe the motor area
- Located in the frontal lobe
- Responsible for voluntary movements by sending signals to the muscles in the body.
Describe the somatosensory area
- Located in the parietal lobe
- Receives sensory information from the skin to produce sensations related to pressure, pain, temperature etc.
- Different parts of the somatosensory area receive messages from different locations of the body.
Describe the visual area
- Located at the back of the brain in the occipital lobe.
- Receives and processes visual information
- Information from the right-hand side visual field is processed in the left hemisphere, and information from the left-hand side visual field is processed in the right hemisphere.
- The visual area contains different parts that process different types of information including colour, shape or movement.
Describe the auditory area
- Located in the temporal lobe
- Responsible for analysing and processing acoustic information.
- Information from the left ear goes primarily to the right hemisphere and information from the right ear goes primarily to the left hemisphere.
- The primary auditory area is involved in processing simple features of sound including volume, tempo and pitch.
What are the two language centres in the brain?
The Broca’s area and Wernicke’s area
Describe the broca’s area
- Motor region is located here.
- Located in the left frontal lobe.
- Responsible for speech production.
What results in damage to the broca’s area?
They can experience Broca’s aphasia which results in slow and inarticulate speech.
Describe Wernicke’s area
- Sensory region is located here.
- Located in the left temporal lobe.
- Responsible for understanding languages.
What results in damage to the Wernicke’s area?
They can experience Wernicke’s aphasia and struggle to comprehend language and often produce sentences that are fluent but meaningless.
Evaluate the localisation of function
- The claim that functions are localised to certain areas of the brain has been criticised. Lashley proposed the equipotentiality theory which suggests that basic motor and sensory functions are localised, but higher mental functions are not. He claimed intact areas of the cortex could take over responsibility for specific cognitive functions following a brain injury. This suggests that functions are not localised to just one region, as other regions can take over specific functions following a brain injury.
- Some psychologists argue that the idea of localisation fails to take into account individual differences. Herasty (1997) found that women have larger Broca’s and Wernicke’s areas than men. This suggests a level of beta bias in the theory, the differences of men and women are ignored.
What is hemispheric lateralisation?
The idea that the two halves of the brain are functionally different and that each hemisphere has specialisations
What is the left hemisphere and right hemisphere dominant for?
Left: dominant for language
Right: Visual motor tasks
How are the two hemispheres connected?
Through nerve fibres called the corpus callosum
Explain split-brain research
Sperry and Gazzaniga (1967)
Aim: To examine the extent the two hemispheres are specialised for certain functions.
Method: They showed images or objects to only 1 side of the brain at a time using visual fields
- LVF goes to RH
- RVF goes to LH
Since the corpus callosum was cut, information was not able to pass to the other side of the brain
Tasks + Findings:
1. Describe what you see
- Image shown to RVF = patients could say what they saw
- Image shown to LVF = patients could not say what they saw because the RH speak and can’t send info to the LH
- Tactile (touch)
- Object in right hand = patients could say what they were holding
- Object in left hand = patients couldn’t say what it was but could pick up a matching object by touch - Drawing
- Image to RVF = right hand was not very good at drawing
- Image to LVF = left hand drew much better even though majority were right-handed
Conclusion: LH = language RH = visual/spatial tasks. Corpus callosum is essential for communication between both hemispheres. Proves that brain is lateralised.
Evaluate split-brain research
Turk et al argued that language may not be restricted only to the left hemisphere. He discovered a patient who had damaged his left hemisphere but developed the capacity to speak in the right hemisphere which eventually lead to him being able to speak about information presented to both sides of his brain
What is brain plasticity?
Refers to the brain’s ability to change and adapt because of experiences.
What is functional recovery and how does the brain do this?
The transfer of functions from a damaged area of the brain after trauma to other undamaged areas.
The brain does this through a process called ‘neuronal unmasking’ where ‘dormant’ synapses (synapses that have not received enough input to be active) open connections to compensate for a nearby damaged area of the brain. This allows new connections in the brain to be activated, thus recovering any damage in specific regions.
Evaluate brain plasticity
Kuhn et al. found an increase in grey matter in various regions of the brain after participants played video games for 30 minutes a day over a two-month period.
Davidson et al showed the permanent change in the brain generated by prolonged meditation. Buddhist monks who meditated frequently had a much greater activation of gamma waves (which coordinate neural activity) than did student with no experience of meditation.
These two studies support the idea of plasticity and the brain’s ability to adapt from new experiences whether it’s video games or meditation.
Evaluate functional recovery
Taijiri et al found that stem cells given to rats after brain trauma showed a clear development of neuron-like cells in the area of injury. Supports the idea of the brain making new connections
Both research examning plasticity and functional recovery lead to application of findings in neurorehabilitation which uses motor therapy and electrical stimulation of the brain to counter the deficits in motor and cognitive functions after accidents/injuries
