Discuss the extent to which brain functions are localised. (16 marks)
Localisation is the theory that different areas of the brain are responsible for different behaviour,
processes. Our brain is divided into two parts the left and right hemisphere and some of our physical
and psychological functions are controlled by particular hemispheres (lateralisation). Activity on the
left side hand side of the body is controlled by the right hemisphere and vice versa. The cortex of
both hemispheres is subdivided into 4 lobes.
Firstly, the motor area which is located at the frontal lobe is responsible for voluntary movement in
the opposite side of the body. Secondly the somatosensory area which is located in the (front of
both) partial lobes is where sensory information from the skin (touch, heat pressure) is represented.
Thirdly the visual area located in the occipital lobe is responsible for processing visual information.
Nerve impulses are transferred from the retina to the visual cortex via optic nerves. Finally, the
auditory area located in the temporal lobe analyses speech based information. Damage to the area
may produce partial hearing loss the more damage the more extensive loss.
Other important areas of the brain are the language centres which are located in the left
hemisphere. The Broca area (left frontal lobe) is responsible for speech production and damage to
this area causes Brocas aphasia which slows speech and affects fluency. Whereas the Wernicke’s
area, (temporal lobe) is responsible for language comprehension (understanding), damage to this
area would cause Wernicke aphasia, where a patient is able to speak but not understand language
and will produce nonsense words as part of their speech.
A strength of localisation is brain scans support it. For example, Peterson et al (1988) used brain
scans to demonstrate how the Wernicke’s area was active during a listening task and the Brocas area
was active during a reading task. This evidence suggests that these areas are distinct and separate as
they are active during different tasks and that many neurological functions are localised, particularly
in relation to language and memory. Moreover, brain scans enable you to see what brain activity is
active in what specific parts of the brain. Thus, this increases the external validity of localisation of
the brain as objective scientific evidence supports it.
Another strength of localisation is case studies support the theory. For example, the case study of
Phineas Gage who suffered from an accident, which resulted in a metal pole exiting his skull taking
most of his brain and the left frontal lobe. This case study supports the localisation of the brain as
damage to his brain resulted in him having a change of behaviour and personality as the area of the
brain responsible for behaviour (frontal lobe) was damaged. However, this study lacks external
validity as case studies are unique one-off case/events and everyone brain may differ thus, you are
unable to generalise findings from this study to the wider population.
A limitation of localisation is that it fails to consider individual differences. For example, Herasty
(1997) found that women have proportionally larger Broca’s and Wernicke’s areas than men, which
can perhaps explain the greater ease of language use amongst women. Thus, we are unable to
generalise research examining localisation of function to male and females equally, as the different
brain structures/sizes suggest that different consideration are required when considering the
different sexes.
Localisation is the theory that different areas of the brain are responsible for different behaviour,
processes. Our brain is divided into two parts the left and right hemisphere and some of our physical
and psychological functions are controlled by particular hemispheres (lateralisation). Activity on the
left side hand side of the body is controlled by the right hemisphere and vice versa. The cortex of
both hemispheres is subdivided into 4 lobes.
Firstly, the motor area which is located at the frontal lobe is responsible for voluntary movement in
the opposite side of the body. Secondly the somatosensory area which is located in the (front of
both) partial lobes is where sensory information from the skin (touch, heat pressure) is represented.
Thirdly the visual area located in the occipital lobe is responsible for processing visual information.
Nerve impulses are transferred from the retina to the visual cortex via optic nerves. Finally, the
auditory area located in the temporal lobe analyses speech based information. Damage to the area
may produce partial hearing loss the more damage the more extensive loss.
Other important areas of the brain are the language centres which are located in the left
hemisphere. The Broca area (left frontal lobe) is responsible for speech production and damage to
this area causes Brocas aphasia which slows speech and affects fluency. Whereas the Wernicke’s
area, (temporal lobe) is responsible for language comprehension (understanding), damage to this
area would cause Wernicke aphasia, where a patient is able to speak but not understand language
and will produce nonsense words as part of their speech.
A strength of localisation is brain scans support it. For example, Peterson et al (1988) used brain
scans to demonstrate how the Wernicke’s area was active during a listening task and the Brocas area
was active during a reading task. This evidence suggests that these areas are distinct and separate as
they are active during different tasks and that many neurological functions are localised, particularly
in relation to language and memory. Moreover, brain scans enable you to see what brain activity is
active in what specific parts of the brain. Thus, this increases the external validity of localisation of
the brain as objective scientific evidence supports it.
Another strength of localisation is case studies support the theory. For example, the case study of
Phineas Gage who suffered from an accident, which resulted in a metal pole exiting his skull taking
most of his brain and the left frontal lobe. This case study supports the localisation of the brain as
damage to his brain resulted in him having a change of behaviour and personality as the area of the
brain responsible for behaviour (frontal lobe) was damaged. However, this study lacks external
validity as case studies are unique one-off case/events and everyone brain may differ thus, you are
unable to generalise findings from this study to the wider population.
A limitation of localisation is that it fails to consider individual differences. For example, Herasty
(1997) found that women have proportionally larger Broca’s and Wernicke’s areas than men, which
can perhaps explain the greater ease of language use amongst women. Thus, we are unable to
generalise research examining localisation of function to male and females equally, as the different
brain structures/sizes suggest that different consideration are required when considering the
different sexes.
