‘Outline and evaluate localisation of function of the brain’ (16 marks)
Localisation is the idea that specific regions of the brain are responsible for different
functions for example language and memory. One region is the motor cortex found in the
frontal lobe region which is responsible for generating voluntary movements. Visual centres
are found in the occipital lobe responsible for visual processing and the auditory centres are
located in both temporal lobes responsible for hearing. The somatosensory cortex is found
in the parietal lobe and its role is to process incoming sensory information for example
sensory receptors for touch. Whilst these mentioned cortexes and centres around generally
found on both hemispheres, Broca’s and Wernicke’s area tend to be generally only on the
left hemisphere each playing a role in speech. Broca’s areas is located in the frontal lobe and
responsible for speech production whereas Wernicke’s area is located in the temporal lobe
and responsible for speech comprehension. As mentioned, these regions are specific and
adapted for their specific functions to ensure information processing and responses are
localised to different regions of the brain.
One advantage of localisation of function of the brain is that it has supporting research for
cases of damaged speech production. For example, a case study of Tan showed that when
he had damaged his Broca’s area in the left hemisphere, the only word he could produce
was ‘Tan’ which shows a deterioration in his ability to produce speech once it was damaged.
Therefore this case of aphasia indicates that there is localised language centres which in
turn increases the external reliability of the theory of localisation of speech centres.
However, on the contrary, the use of case studies such as Tan can rise some methodological
criticisms. For example, when using case studies , these are rare occurrences which cannot
be tested on a wider scale as it would be unethical to damage a large sample of people’s
Broca’s area to see if they have the same results as Tan. Therefore this means that in Tan’s
case, this may have been a case of individual differences in the way his body reacted to
trauma in the brain which in turn makes it harder to generalise his results for a larger
population thus reducing the internal validity of the theory.
Another disadvantage of localisation theory is that there is contradictory research. For
example, Lashley proposed the equipotentiality theory which suggests that the basic motor
and sensory functions are localised but higher mental functions aren’t. this means that
following a brain injury, areas of the cortex could take over responsibility for specific
cognitive functions. Therefore this casts a doubt on theories about localisation of functions
suggesting that functions aren’t localised to just one region thus the theory of localisation
doesn’t have a full overview of the functioning of the brain and its regions.
Another disadvantage of the theory of localisation is that psychologists argue that it is more
important to investigate how the brain communicates with eachother rather than focusing
on specific regions of the brain. For example, Wernicke suggested that although different
areas of the brain are independent they must interact with eachother in order to function
such as Dejerine’s case in which the connection between the visual centre and the
Wernicke’s area was damaged causing him to have an inability to read. Therefore this shows
how functions such as language rely on connections of centres rather than just one specific
region, thus making the theory of localisation lose credibility and oversimplified.
, Another disadvantage of localisation is that it fails to take into account individual
differences. For example, Herasty found that women tend to have a larger Broca and
Wernicke area than men which can help understand the greater ease of language use
amongst women. Therefore, this raises concerns on beta bias in the theory as the variations
between the genders have been minimised and ignored thus additional factors have not
been considered reducing the validity of the theory and generalisability.
Localisation is the idea that specific regions of the brain are responsible for different
functions for example language and memory. One region is the motor cortex found in the
frontal lobe region which is responsible for generating voluntary movements. Visual centres
are found in the occipital lobe responsible for visual processing and the auditory centres are
located in both temporal lobes responsible for hearing. The somatosensory cortex is found
in the parietal lobe and its role is to process incoming sensory information for example
sensory receptors for touch. Whilst these mentioned cortexes and centres around generally
found on both hemispheres, Broca’s and Wernicke’s area tend to be generally only on the
left hemisphere each playing a role in speech. Broca’s areas is located in the frontal lobe and
responsible for speech production whereas Wernicke’s area is located in the temporal lobe
and responsible for speech comprehension. As mentioned, these regions are specific and
adapted for their specific functions to ensure information processing and responses are
localised to different regions of the brain.
One advantage of localisation of function of the brain is that it has supporting research for
cases of damaged speech production. For example, a case study of Tan showed that when
he had damaged his Broca’s area in the left hemisphere, the only word he could produce
was ‘Tan’ which shows a deterioration in his ability to produce speech once it was damaged.
Therefore this case of aphasia indicates that there is localised language centres which in
turn increases the external reliability of the theory of localisation of speech centres.
However, on the contrary, the use of case studies such as Tan can rise some methodological
criticisms. For example, when using case studies , these are rare occurrences which cannot
be tested on a wider scale as it would be unethical to damage a large sample of people’s
Broca’s area to see if they have the same results as Tan. Therefore this means that in Tan’s
case, this may have been a case of individual differences in the way his body reacted to
trauma in the brain which in turn makes it harder to generalise his results for a larger
population thus reducing the internal validity of the theory.
Another disadvantage of localisation theory is that there is contradictory research. For
example, Lashley proposed the equipotentiality theory which suggests that the basic motor
and sensory functions are localised but higher mental functions aren’t. this means that
following a brain injury, areas of the cortex could take over responsibility for specific
cognitive functions. Therefore this casts a doubt on theories about localisation of functions
suggesting that functions aren’t localised to just one region thus the theory of localisation
doesn’t have a full overview of the functioning of the brain and its regions.
Another disadvantage of the theory of localisation is that psychologists argue that it is more
important to investigate how the brain communicates with eachother rather than focusing
on specific regions of the brain. For example, Wernicke suggested that although different
areas of the brain are independent they must interact with eachother in order to function
such as Dejerine’s case in which the connection between the visual centre and the
Wernicke’s area was damaged causing him to have an inability to read. Therefore this shows
how functions such as language rely on connections of centres rather than just one specific
region, thus making the theory of localisation lose credibility and oversimplified.
, Another disadvantage of localisation is that it fails to take into account individual
differences. For example, Herasty found that women tend to have a larger Broca and
Wernicke area than men which can help understand the greater ease of language use
amongst women. Therefore, this raises concerns on beta bias in the theory as the variations
between the genders have been minimised and ignored thus additional factors have not
been considered reducing the validity of the theory and generalisability.
