Localisation of function in the brain

• Broca and Wernicke
• Specific areas associated with physical and psychological functions
• Before this, scientists supported holistic theory of the brain (all parts responsible in processing thoughts and action)
• Broca and Wernicke argued for localisation of function (cortical specialisation)
• Different parts of the brain perform different tasks and are involved with different parts of the body
• If certain area damaged, function is also affected.

P- A strength of localisation of function is that there is brain scan evidence of localisation.

E- Peternsen et al. (1988) used brain scans to demostrate how Wernicke's area was active during a listening task and Broca's area was active during a reading task, suggesting that these areas of the brain have different functions. Similarly, the study of long-term memory conducted by Tulving et al. found that semantic and episodic memories reside in different parts of the prefrontal cortex.

C- However, there is also evidence that the brain can change in response to trauma or other stimuli. For example, Maguire et al. found a greater volume of brain matter in the posterior hippocampus of London taxi drivers (who must have an extensive knowledge of London roads) compared to a control group. This suggests that brain function is not fixed to the extent that is previously suggested.

E- Despite this, there now exists a wealth of highly sophisticated and objective methods for measuring activity in the brain which provide sound scientific evidence of localisation of brain function. This is therefore a strength.

• Brain divided into two halves called left and right hemispheres
• Control of physical and psychological functions dominated by particular hemisphere - lateralisation
• Activity in right side controlled by left hemispher and vice versa
• Outer layer of both hemispheres is the cerebral cortex.
• Around 3mm thick and is what separates us from other animals as the human cortex is more developed.
• Appears grey due to location of cell bodies.

P- Another strength of this approach is that there is neurosurgical evidence.

E- Surgical removal of areas of the brain to control aspects of behaviour was developed in the 1950s. Early attempts, such as the lobotomy (developed by Walter Freeman), were brutal and imprecise, typically involving searing connections from the frontal lobe in an attempt to control aggressive behaviour. Neurosurgery is still sparingly used today in extreme cases of obsessive compulsive disorder and depression. For example, Dougherty et al. (2002) reported on 44 OCD patients who had undergone and cingulotomy - a neurosurgical procedure that involves lesioning of the cingulate gyrus. At post-surgical follow up after 32 weeks, a third had met the criteria for successful response to the surgery and 14 percent for a partial response.

C- However, these results mean that the majority of patients didn't even have a partial success and therefore underwent surgery with no result. This suggests that a more developed understanding of the brain and relationships between areas is required.

E- Nevertheless, even the partial success of procedures like this suggests that symptoms and behaviours associated with serious mental disorders are localised.

• • Motor area
  • Back of the frontal lobe
  • Controls voluntary movement
  • Damage result in loss of fine movement control
• Somatosensory area
  • Separated from motor area by central sulcus
  • Where sensory info from skin represented
  • Amount of area dedicated denotes sensitivity
• Visual area
  • Back of occipital lobe
  • Damage to one hemisphere may cause blindless in opposite eye.
• Auditory area
  • Temporal lobes
  • Speech-based info
  • The more extensive the damage, the more extensive the loss
  • Damage to specific area (Wernicke) may affect language

• Broca's area
  • Speech production
  • Damage may lead to Broca's aphasia
  • Speech is slow, labourous and lacking in fluency
• Wernicke's area
  • Responsible for speech comprehension
  • Wernicke's aphasia when damaged
  • Nonsense words

• Phineas Gage
  • Change in temperament after damage to the frontal lobe

• Argument against localisation
• When brain is damaged, brain appears to attempt to recover from lost function