— Localisation of Function in the Brain

• The motor area = found in the frontal lobe, this area is involved in regulating and coordinating movements. Lesions or damage in the motor area result in an inability to control voluntary fine motor movements.
• The auditory area = An area of the temporal lobe, which is responsible for processing auditory information and speech. Lesions or damage in the auditory area causes hearing loss, whereas damage to specific parts of the auditory area (Wernicke’s area) results in Wernicke’s aphasia.
• The visual area = An area in the occipital lobe which is responsible for processing visual information.
• The somatosensory area = An area of the parietal lobe which processes information associated with the senses e.g. touch, heat, pressure etc. Lesions in this area result in a loss of ability to denote sensitivity to particular bodily areas.
• Wernicke’s Area = Responsible for speech comprehension and located in the left temporal lobe. damage (e.g. through stroke and trauma) results in Wernicke’s aphasia, which is characterised by the use of nonsensical words (called syllogisms), no awareness of using incorrect words, but no issues with pronounciation and intonation.
• Broca’s Area = Responsible for speech production and located in the frontal lobe, usually in the left hemisphere. damage results in Broca’s aphasia, characterised by difficulty forming complete sentences and understanding sentences, as well as failing to understand the order of words in a sentence and who they are directed towards i.e. I, you, we, him, me etc.
• Overall, the left hemisphere of the brain is associated with language production and comprehension. Therefore, language is an example of a cognitive ability which is both localised and lateralised (to the left hemisphere).
• Supporting Case Studies = Phineas Gage was injured by a rod which which teared through his prefrontal cortex. The damage involved both left and right prefrontal cortices that causes a defect in rational decision making and the processing of emotion”. Such case studies, particularly those showing marked differences after trauma, demonstrate the idea that some areas of the brain are responsible for specific functions.
• However, with the use of case studies, the subjectivity of the conclusions drawn and the unusual sample, alongside a lack of control over confounding and extraneous variables, must also be considered.
• Contradictory Theory = The opposite to localisation theory would be a holistic view of brain function, suggesting that each function requires several brain areas to be activated and that these functions are not restricted to these areas. since, after removing 20-50% of the cortices belonging to rats, found that no specific brain area was associated with learning how to go through a maze.
• This suggests that intelligence, or even learning, is too complex to be restricted to certain areas of the brain. Therefore, this suggests that localisation theory may provide a better explanation for ‘simple’, rather than complex, brain functions.
• Supporting evidence for localisation of brain function = Petersen et al (1988) , who found that Wernicke’s area activation is required for listening tasks, whereas Broca’s area is required for reading tasks. This confirms the idea that Wernicke’s area is involved in speech comprehension, whilst brocas area is responsible for language production.