localisation of function in the brain
evaluation
the 4 brain areas
localisation vs holistic theory
localisation = argued by broca & wernicke, the idea that different parts of the brain perform different tasks & are involved with different parts of the body - if a certain area becomes damaged, its function will also be affected
holistic theory = all parts of the brain are involved in the processing of thought & action
competing theories
brain hemispheres
the main part of the brain (the cerebrum) is divided into 2 symmetrical halves: left hemisphere & right hemisphere
lateralisation = some physical & psychological functions are controlled/dominated by a particular hemisphere
activity on left side of body is controlled by right hemisphere & vice versa
cerebral cortex = outer layer of both hemispheres
motor area
- back of frontal lobe
- controls voluntary movement on opposite side of body
- damage = loss of control over fine movements
somatosensory area
- front of both parietal lobes
- is where sensory information from skin is represented
- damage = decreased sensory thresholds
visual area
- in occipital lobes
- each eye sends information from right visual field to left visual cortex, & vice versa
- damage = reduced vision in right field of both eyes, if occurred in left hemisphere
auditory area
- in temporal lobes
- analyses speech-based information
- damage = reduced hearing or deafness
language centres of the brain
language is restricted to left side of the brain in most people
broca's area
- small area in left frontal lobe
- responsible for speech production
- damage = broca's aphasia - slow, laborious speech
wernicke's area
- small area in left temporal lobe
- responsible for language understanding
- damage = wernicke's aphasia - nonsense words (neologisms)
blue = frontal lobe
yellow = parietal lobe
green = temporal lobe
pink = occipital lobe
bottom = cerebellum - fine delicate movement, balance & dexterity
strengths
limitations
damage to areas of the brain has been linked to mental disorders
- neurosurgery = last resort method for treating some mental disorders, targeting specific areas
- a researcher found that 32 weeks after surgery, around 30% of patients had met the criteria for successful response to cingulotomy & 14% for partial response
- cingulotomy = isolating the cingulate gyrus
- this success suggests behaviours associated with serious mental disorders may be localised
language may not be localised just to broca and wernicke's areas
- research found only 2% of modern researchers think that language in the brain is completely controlled by these 2 areas
- advances in brain imaging techniques mean neural processes can be studied with more clarity than ever before
- seems it is distributed far more holistically than first thought, eg in thalamus
- suggests language may be organised more holistically in the brain, contradicting localisation theory
evidence from brain scans supporting the idea that many everyday brain functions are localised
- a researcher used brain scans to find that wernicke's area was active during a listening task, and broca's area in a reading one
- this confirms localised areas for everyday behaviours
- therefore, objective methods have provided good scientific evidence that many brain functions are localised
(counterpoint to evidence from brain scans) - challenging evidence
- a researcher found that no area was found to be more important than another in terms of rats' ability to learn a route after areas of the cortex were removed
- learning appeared to require all areas of the cortex
- suggests that higher cognitive processes, eg learning, aren't localised but instead distributed more holistically in the brain
brain stem = sends signals from your brain to the rest of your body & controls many subconscious body functions, such as breathing, heart rate & thirst/hunger