Essay
ESSAY Discuss localisation of function in the human brain
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Full mark biopsychology essay.
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Discuss localisation of function in the human brain. (16 marks)Localisation of function is the idea that different parts of the brain are responsible for different,
specialised functions. Damage to certain parts of the brain will impair the function that that region was
responsible for. The motor cortex – located in the frontal lobes – control voluntary movement; this
function is also specialised laterally, with the left hemisphere controlling the right side of the body and
vice versa. The somatosensory cortex – located in the parietal lobes – is responsible for detecting and
representing sensory information from the skin, such as temperature and pain. The visual cortex –
occipital lobes – deals with visual information, and the auditory cortex – temporal lobes – deals with
auditory information.
The language centres are located in the left hemisphere. Broca used post-mortem examinations
to identify that Broca’s aphasia – the ability to understand language but the inability to produce it – was
associated with damage to the left frontal lobe; it was therefore concluded that the Broca’s area
(located in the left frontal lobe) is responsible for speech production. Similarly, Wernicke studied
Wernicke’s aphasia – where nonsense speech is produced – and concluded that the Wernicke’s area
(located in the left temporal lobe) is responsible for language comprehension.
A limitation of localisation of function is that evidence for brain plasticity and functional
recovery support the idea of a holistic brain. Some stroke patients are able to recover, because other
areas of the brain compensate and take over the function of the damaged region. This suggests that the
brain works as one whole unit, rather than several specialist regions. Furthermore, individuals who are
born blind often have other senses – such as touch – enhanced, due to the redundant visual area of the
brain being used for other skills. Lashley describes this as the brain’s equipotentiality; the idea that each
part of the brain has equal potential to develop different functions directly contradicts the idea of
localisation of function, and therefore limits it.
A limitation of localisation of function is that evidence supporting the Broca’s and Wernicke’s
areas comes from post-mortem examinations, and these can be unreliable. It may be that the damage
seen in the brain was unrelated to the symptoms of aphasia, or that confounding variables – such as
cause of death and age – were present. The sample sizes studied would have been small, and it may be
inappropriate to generalise these few case studies universally. Not only this, but new interpretations of
Broca’s research suggest that the observed damage was actually more widespread, and that damage to
the Broca’s area only would cause temporary – and not permanent – problems. However, Petersen used
brain imaging to demonstrate that the Wernicke’s area was active during listening tasks, and that the
Broca’s area was active during reading tasks. This strengthens the idea of localisation of function by
clearly showing that these two specialist regions have specialist functions, but also strengthens the
credibility of psychology as a science as brain scans provide scientific, objective evidence.
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