Localisation of Brain Function Flashcards
Holistic Theory –> Localisation Theory
1) Holistic theory used to suggest all parts of brain were involved in processing thought and action.
2) But specific areas of brain were later linked with specific functions (localisation theory) - if an area of brain is damaged the function associated is also affected.
2 Hemispheres & Lateralisation
Brain is divided into 2 hemispheres & lateralised.
1) Corpus callosum connects hemispheres, which allows the two to communicate.
2) Lateralisation - each hemisphere has a specialised function.
E.g. Left side of body controlled by right hem & right side is controlled by left hem - controlled by opposite sides.
Left/Right Brain
Left Brain:
- language
- logic
- numbers
- analysing
Right Brain:
- expressing emotion
- music
- creativity
- colour/ images
Cerebral Cortex
1) The outer layer of brain (3mm thick) & it is what separates us from lower animals as it is highly developed.
2) Cortex appears grey due to location of cell bodies - hence phrase ‘grey matter’.
3) CC of both hemispheres is divided into 4 lobes:
- Frontal –> motor area
- Parietal –> somatosensory area
- Occipital –> visual area
- Temporal –> auditory area
4 Lobes & Associated Areas
1) Motor Area - (back of frontal lobe)
Controls voluntary movement - damage may result in loss of control over fine motor movements.
2) Somatosensory Area - (front of parietal lobes)
Processes sensory info from skin (touch, heat, pressure, etc.) - amount of somatosensory area devoted to a particular body part denotes its sensitivity.
3) Visual Area - (occipital lobe)
Each eye sends info from right visual field to the left visual cortex, & from left visual field to right visual cortex.
4) Auditory Area - (temporal lobe)
Analyses speech-based info - damage may produce partial hearing loss, the more extensive the damage, the more serious the loss.
Language Centres
1) Broca’s Area - Speech production
2) Wernicke’s Area - Language understanding
Broca’s Area
1) In left frontal lobe - Damage causes Broca’s aphasia which is characterised by speech that is slow, laborious & lacking in fluency.
2) Broca’s patients may have difficulty finding words & naming certain objects.
Wernicke’s Area
1) In left temporal lobe - Ppl with Wernicke’s aphasia produce language but have problems understanding it, so they produce fluent but meaningless speech - often produce nonsense words as part of the content of their speech.
Strength of Localisation Theory
SUPPORT FROM NEUROSURGERY
1) Neurosurgery is used to treat mental disorders.
2) Dougherty et al. studied 44 ppl with OCD who had a cingulotomy. At a follow-up, 30% met criteria for correct response & 14% for partial response.
–> Success of such procedures strongly suggests that behaviours associated with mental disorders may be localised.
Strength of Localisation Theory
SUPPORT FROM BRAIN SCANNING
1) Peterson et al. used brain scans to show activity in Wernicke’s area during a listening task & in Broca’s area during a reading task.
2) A study of long-term memory by Tulving et al. revealed semantic & episodic memories are located in different parts of prefrontal cortex.
–> There is now lots of sophisticated & objective methods to measure brain activity - providing scientific evidence of localisation of function.
Limitation of LT
LANGUAGE ORGANISED MORE HOLISTICALLY
1) Dick and Tremblay found very few researchers still believe language is only in Broca’s & Wernicke’s areas –> advanced techniques (e.g. fMRI) have identified regions in right hemisphere & the thalamus.
–> Suggests rather than being confined to a few key areas, language may be organised more holistically in the brain - which contradicts localisation theory.
