Localisation of brain function

• localisation

  is the idea that certain functions e.g. language have certain areas of the brain which are specialised for that certain function.
• Areas of the brain

  -Motor cortex: found at the back of frontal lobes. It involves planning, executing and control of motor movement. Damage to motor area may result in loss of mobility and motor functioning in opposite side of the body.

  -Somatosensory cortex: located front of parietal lobe behind motor cortex and are separated by central sulcus. It receives and processes sensory information detected from opposite side of the body. Sensitivities like touch, temperature and pressure. Damage can lead to loss of sensitivity and difficult to recognise objects by tactile sensations.
• Areas of the brain

  -Visual cortex: Right visual cortex (RVC) receives and processes info within the left visual cortex (LVC). LVA receives and processes info within right visual cortex. Damage to the LVC leads to the inability to process info in the RVF (reduces vision in both eyes).

  -Auditory cortex: found in left and right temporal lobes. Responsible for receiving and processing sound/speech related information. Damage to the left auditory area means issues with processing and analysing auditory information like volume and tempo. Any auditory info received by the opposite ear.
• Language centres in the brain 


  -Broca's area: involved in language production and fluency production, both localised and lateralised but only to the left hemisphere. Damage to area can lead to Broca's aphesis which leads to difficultly in producing language, speech is slurred, lacks fluency and poor grammar meaning speech lacks fluency.
• Language centres in the brain


  -Wernicke's area: involved in understanding the meaning of language comprehension. Localised and lateralised to the left hemisphere. Damage results in Wernicke's aphesis and fluent aphesis which is where speech retains fluency but words lack meaning so language is difficult to comprehend.
• Evaluation - research support

  -Brain imaging studies to support some functions are localised to specific areas of the brain.

  -Maguire studied black cab drivers and compared them to a control group. She compared structural MRI scans and it revealed significantly more grey matter in the hippocampus in taxi drivers. This supports spatial navigation memory is localised to the posterior hippocampus.

  -Petersen: Carried out PET scans which revealed Wernicke's area active during listening task and Broca's area active during reading task.
• Evaluation - Contradictory evidence for localisation

  -Lashley: some aspects of human processing are too complex to be strictly localised.

  -Learning is not localised, but distributed holistically throughout cerebral cortex.

  -Lashley got rats to learn a maze route and after destroyed 10-50% of the cerebral cortex of rats brain.

  -Rat completed the maze which suggests no one area is responsible for learning.

  -This suggests learning requires the whole cerebral cortex.
• Evaluation - case studies

  +Clive wearing was attacked by a virus which damaged his hippocampus which resulted in amnesia. This meant he was unable to form new LTM after dame to the hippocampus. This supports that memory is localised to the hippocampus.

  +Phineas Gauge had a metal pole impaled through his left frontal lobe. Motor movement and memory was unaffected but his personality changed as he became impatient and selfish. This supports that personality is localised to frontal lobes. Issues with replication
• Case study - doesn't support localisation, supports brain plasticity


  -EB had a left hemispherectomy at the age of 2 as he had a tumour removed. This resulted in extreme aphasia due to the absence of Broca's and Wernicke's area. Therefore, supporting that language is lateralised to the left hemisphere.

  -However, he had a gradual recovery as at the age of 17 his language functioning was near to normal. This suggests language can be lateralised to right hemisphere. Shows how brain plasticity can mean functions which were once lateralised can be redistributed to another hemisphere.