localisation of function Flashcards
(28 cards)
what is localisation of function?
- theory that different areas of the brain are responsible for specific processes or activities
- if a certain area of the brain becomes damaged through illness or injury, the function associated with that area will also be affected
how is the cerebrum divided?
2 symmetrical halves called the left and right hemisphere
what is lateralisation?
the idea that some of our physical and psychological functions are controlled or dominated by a particular hemisphere
what is activity on the left or right-hand side of the body controlled by?
- activity on the left-hand side of the body is controlled by the right hemisphere
- activity on the right-hand side of the body is controlled by the left hemisphere
what is the cortex of both hemispheres divided into?
4 centres called lobes
what are the four lobes of the brain?
- the frontal lobe
- the parietal lobe
- the occipital lobe
- the temporal lobe
what is a lobe?
- a part of an organ that is separate in some way from the rest
- each lobe in the brain is associated with different functions
describe the motor area
- back of frontal lobe in both hemispheres
- controls voluntary movement in opposite side of body
what might damage to the motor area result in?
loss of control over fine movements
describe the somatosensory area
- at the front of both parietal lobes
- where sensory information from the skin (eg. related to touch, heat, pressure etc.) is represented
- amount of SA devoted to a particular body part denotes its sensitivity
> eg. receptors for our hands and face occupy over half of the area
describe the visual area
- in the occipital lobe at the back of the brain
- each eye sends information from the RVF to the left visual cortex and vice versa
- therefore, damage to the LH can produce blindness in part of the RVF in both eyes
describe the auditory area
- in the temporal lobes
- analyses speech-based information
what may damage to the temporal lobe result in?
- partial hearing loss
- the more extensive the damage, the more extensive the loss
- damage to a specific area of the temporal lobe, wernicke’s area, may affect the ability to comprehend language
describe broca’s area
a small area in the left frontal lobe responsible for speech production
what does damage to broca’s area result in and describe the condition
- broca’s aphasia
- characterised by speech that is slow, laborious and lacking in fluency
- difficulty with prepositions and conjuctions (a, the and etc.)
describe broca’s most famous patient
- ‘tan’
- this was the only word he could say
describe wernicke’s area
region in the left temporal lobe which is responsible for language understanding
describe wernicke’s aphasia
- caused when wernicke’s area is damaged
- can produce language but severe difficulties understanding it
- the speech they produce is fluent but meaningless
- produce nonsense words (neologisms) as part of the content of their speech
evaluation: evidence from neurosurgery (dougherty et al. 2002)
- reported on 44 people with OCD who had undergone a cingulotomy, which involves isolating the cingulate gryus as a last resort method of treating OCD
- at post-surgical follow-up after 32 weeks, about 30% had met the criteria for successful response to the surgery and 14% for partial response
- the success of these procedures suggests that behaviours associated with serious mental disorders may be localised
evaluation: evidence from brain scans supports the idea that many everyday brain functions are localised (petersen et al. 1988)
- used brain scans to demonstrate how wernicke’s area was active during a listening task and broca’s area was active during a reading task
- confirms localised areas for everyday behaviours
- therefore, objective methods for measuring brain activity have provided sound scientific evidence that many brain functions are localised
evaluation: evidence from brain scans supports the idea that many everyday brain functions are localised (buckner and petersen 1996)
semantic memory is located on the left side of the PFC, episodic memory on the right
evaluation: challenge to localisation theory (lashley 1950)
- lashley removed areas of the cortex (between 10-50%) in rats that were learning the route through a maze
- no area was proven to be more important than any other area in terms of the rats’ ability to learn the route
- the process of learning seemed to require every part of the cortex rather than being confined to a particular area
- this suggests that higher cognitive processes, such as learning, are not localised, but distributed in a more holistic way in the brain
evaluation: language may not be localised to just broca’s and wernicke’s areas (dick and tremblay 2016)
- only 2% of modern researchers think that language in the brain is completely controlled by broca’s and wernicke’s areas
- advances in brain imaging technqiues, such as fMRI, mean that neural processes in the brain can be studied with more clarity than every before
- language function seems to be distributed far more holistically in the brain than was first thought
- language streams have been identified across the cortex, including brain regions in the right hemisphere, as well as subcortical regions such as the thalamus
- this suggests that, rather than being confined to a couple of key areas, language may be organised more holistically in the brain, which contradicts localisation theory
evaluation: issues with case study evidence
- difficult to make meaningful generalisations from the findings of a single individual
- conclusions drawn may depend on the subjective interpretation of the researcher