Discuss localisation of function (16 marks)
A01
Localisation vs holistic theory -
Localisation of function: the theory that different areas of the brain are responsible for specific behaviour,
processes or activities.
Holistic theory: all parts of the brain are involved in the processing of thought and action.
Hemispheres of the brain-
The brain is divided into two hemispheres. The outer layer of both hemispheres is called the cerebral cortex.
Some of our functions are controlled by a specific hemisphere (lateralisation). The left-hand side of the body
= right hemisphere and vice versa - contralateral.
A01
4 Lobes in the brain:
1) Frontal lobe
Motor cortex (both hemispheres) - controls voluntary movement on the opposite side of the body.
Broca's area (left hemisphere) - speech production - if damaged causes Broca's aphasia e.g. case study - Tan.
2) Parietal lobe
Somatosensory area (both hemispheres) - sensory information from the skin is represented.
3) Occipital lobe
Visual area (both hemispheres) - info from RVF to LVC and vice versa.
4) Temporal lobe
Auditory area (both hemispheres) - analyses speech-based information.
Wernicke's area (left hemisphere) - language comprehension - if damaged causes Wernicke's aphasia.
A03
One strength is that damage to specific areas of the brain has been linked to mental disorders. Neurosurgery
(a last resort method of treatment for mental disorders) has shown that by targeting specific areas of the brain
that are involved in the disorder e.g. in a cingulotomy for treatment of OCD 30% of 44 pp’s had a successful
response to surgery. This suggests that behaviours associated with serious mental disorders may be localised.
A03
One strength is evidence from brain scans which support the idea that many everyday brain functions are
localised. Brain scans were used to demonstrate how Wernicke's area was active during a listening task and
Broca's area was active during a reading task. This confirms localised areas for everyday behaviours.
However…
In a study which removed areas of the cortex (10%- 50%) in rats that were learning a route to a maze, no area
was proven to be more important than any other in terms of their ability to learn the route. This suggests that
higher cognitive processes, e.g. learning, are not localised but distributed holistically in the brain.
A03
One limitation is that language may not be localised just to Broca and Wernicke's areas. Advances in brain
imaging techniques e.g. fMRI, mean that neural processes can be studied with more clarity than ever before.
Language is distributed far more holistically in the brain than first thought. This suggests that rather than
being confined to a couple of key areas, language is more holistic.
A03
One strength is case study evidence, unique cases of neurological damage support localisation theory, such as
Phineas Gage. After suffering from trauma to the brain Gage’s personality shifted as he became more angry
and irritable. This supports the theory of localisation.
However…
Case study evidence is rare and unique and therefore should not be used to make meaningful generalisations
to the target population from the findings of a single individual. Conclusions drawn may also depend on the
subjective interpretation of the researcher.
, Discuss research into hemispheric lateralisation and split brain research (16 marks)
A01
Hemispheric lateralisation -
The idea is that the two hemispheres of the brain are functionally different and that certain mental processes
are mainly controlled by one hemisphere rather than the other e.g. language.
Left and right hemispheres -
Language is lateralized to the left hemisphere.
Left hemisphere: eg Broca's area (left frontal lobe) eg Wernicke's area (left temporal lobe) (analyser)
Right hemisphere: Contributes emotional context (synthesiser)
A01
Sperry’s research -
Split brain: an operation which involves severing the connection of the corpus callosum between RH and LH.
A last resort procedure to reduce epilepsy. The hemispheres can't communicate with each other.
Procedure: 11 people performed 3 tests -
Test 1) Describe what you see
Shown an image in the right visual field (processed in the left visual cortex) (contralateral) asked to describe
what they saw then vice versa.
Findings: Description was better when shown in the right visual field and processed in the left visual cortex
due to language production being in the left hemisphere.
Test 2) Tacktile test
An object placed in the pp's right hand (processed in the left hemisphere) asked to describe what they could
feel then vice versa.
Findings: Description was better when the object was placed in the right hand and processed in the left
hemisphere due to language production being in the left hemisphere.
Test 3) Drawing test
The picture presented to the left visual field ( processed by the right hemisphere) asked to draw what they
saw then vice versa.
Findings: The left hand (controlled by the right hemisphere) would consistently draw clearer and better
pictures than the right-hand (even though all the participants were right-handed). Due to visual motor tasks
being in the right hemisphere.
A03
One limitation is that research has suggested that lateralisation changes with age. Szaflarski et al. found that
language became more lateralised to the left hemisphere with increasing age in children and adolescents, but
after the age of 25, lateralisation decreased with each decade of life. This raises questions about lateralisation,
such as whether everyone has one hemisphere that is dominant over the other and whether this dominance
changes with age.
A03
One limitation is that the split-brain procedure is rarely carried out nowadays. Many studies are presented
with as few as 3 pps. Conclusions are sometimes drawn from participants who either have a confounding
physical disorder that made the split-brain procedure necessary or have had a less complete sectioning of the
two hemispheres than was originally believed. As a result, patients who have had this procedure without
these confounding factors are rarely encountered in sufficient numbers to be useful for research.
However…
Even though the sample size is small, all patients are studied in a lot of detail, case studies often shed light on
aspects of human thinking and behaviour that would be unethical or impractical to study in other ways.
A03
One strength of research into hemispheric lateralisation is that positive functions have been identified. The
main advantage of brain lateralisation is that it increases neural processing capacity (multitasking). Rogers et
al. found that in a domestic chicken, brain lateralisation is associated with an enhanced ability to perform two
tasks simultaneously (finding food and being vigilant for predators). Using only one hemisphere to engage in
a task leaves the other hemisphere free to engage in other functions. This provides evidence for the
A01
Localisation vs holistic theory -
Localisation of function: the theory that different areas of the brain are responsible for specific behaviour,
processes or activities.
Holistic theory: all parts of the brain are involved in the processing of thought and action.
Hemispheres of the brain-
The brain is divided into two hemispheres. The outer layer of both hemispheres is called the cerebral cortex.
Some of our functions are controlled by a specific hemisphere (lateralisation). The left-hand side of the body
= right hemisphere and vice versa - contralateral.
A01
4 Lobes in the brain:
1) Frontal lobe
Motor cortex (both hemispheres) - controls voluntary movement on the opposite side of the body.
Broca's area (left hemisphere) - speech production - if damaged causes Broca's aphasia e.g. case study - Tan.
2) Parietal lobe
Somatosensory area (both hemispheres) - sensory information from the skin is represented.
3) Occipital lobe
Visual area (both hemispheres) - info from RVF to LVC and vice versa.
4) Temporal lobe
Auditory area (both hemispheres) - analyses speech-based information.
Wernicke's area (left hemisphere) - language comprehension - if damaged causes Wernicke's aphasia.
A03
One strength is that damage to specific areas of the brain has been linked to mental disorders. Neurosurgery
(a last resort method of treatment for mental disorders) has shown that by targeting specific areas of the brain
that are involved in the disorder e.g. in a cingulotomy for treatment of OCD 30% of 44 pp’s had a successful
response to surgery. This suggests that behaviours associated with serious mental disorders may be localised.
A03
One strength is evidence from brain scans which support the idea that many everyday brain functions are
localised. Brain scans were used to demonstrate how Wernicke's area was active during a listening task and
Broca's area was active during a reading task. This confirms localised areas for everyday behaviours.
However…
In a study which removed areas of the cortex (10%- 50%) in rats that were learning a route to a maze, no area
was proven to be more important than any other in terms of their ability to learn the route. This suggests that
higher cognitive processes, e.g. learning, are not localised but distributed holistically in the brain.
A03
One limitation is that language may not be localised just to Broca and Wernicke's areas. Advances in brain
imaging techniques e.g. fMRI, mean that neural processes can be studied with more clarity than ever before.
Language is distributed far more holistically in the brain than first thought. This suggests that rather than
being confined to a couple of key areas, language is more holistic.
A03
One strength is case study evidence, unique cases of neurological damage support localisation theory, such as
Phineas Gage. After suffering from trauma to the brain Gage’s personality shifted as he became more angry
and irritable. This supports the theory of localisation.
However…
Case study evidence is rare and unique and therefore should not be used to make meaningful generalisations
to the target population from the findings of a single individual. Conclusions drawn may also depend on the
subjective interpretation of the researcher.
, Discuss research into hemispheric lateralisation and split brain research (16 marks)
A01
Hemispheric lateralisation -
The idea is that the two hemispheres of the brain are functionally different and that certain mental processes
are mainly controlled by one hemisphere rather than the other e.g. language.
Left and right hemispheres -
Language is lateralized to the left hemisphere.
Left hemisphere: eg Broca's area (left frontal lobe) eg Wernicke's area (left temporal lobe) (analyser)
Right hemisphere: Contributes emotional context (synthesiser)
A01
Sperry’s research -
Split brain: an operation which involves severing the connection of the corpus callosum between RH and LH.
A last resort procedure to reduce epilepsy. The hemispheres can't communicate with each other.
Procedure: 11 people performed 3 tests -
Test 1) Describe what you see
Shown an image in the right visual field (processed in the left visual cortex) (contralateral) asked to describe
what they saw then vice versa.
Findings: Description was better when shown in the right visual field and processed in the left visual cortex
due to language production being in the left hemisphere.
Test 2) Tacktile test
An object placed in the pp's right hand (processed in the left hemisphere) asked to describe what they could
feel then vice versa.
Findings: Description was better when the object was placed in the right hand and processed in the left
hemisphere due to language production being in the left hemisphere.
Test 3) Drawing test
The picture presented to the left visual field ( processed by the right hemisphere) asked to draw what they
saw then vice versa.
Findings: The left hand (controlled by the right hemisphere) would consistently draw clearer and better
pictures than the right-hand (even though all the participants were right-handed). Due to visual motor tasks
being in the right hemisphere.
A03
One limitation is that research has suggested that lateralisation changes with age. Szaflarski et al. found that
language became more lateralised to the left hemisphere with increasing age in children and adolescents, but
after the age of 25, lateralisation decreased with each decade of life. This raises questions about lateralisation,
such as whether everyone has one hemisphere that is dominant over the other and whether this dominance
changes with age.
A03
One limitation is that the split-brain procedure is rarely carried out nowadays. Many studies are presented
with as few as 3 pps. Conclusions are sometimes drawn from participants who either have a confounding
physical disorder that made the split-brain procedure necessary or have had a less complete sectioning of the
two hemispheres than was originally believed. As a result, patients who have had this procedure without
these confounding factors are rarely encountered in sufficient numbers to be useful for research.
However…
Even though the sample size is small, all patients are studied in a lot of detail, case studies often shed light on
aspects of human thinking and behaviour that would be unethical or impractical to study in other ways.
A03
One strength of research into hemispheric lateralisation is that positive functions have been identified. The
main advantage of brain lateralisation is that it increases neural processing capacity (multitasking). Rogers et
al. found that in a domestic chicken, brain lateralisation is associated with an enhanced ability to perform two
tasks simultaneously (finding food and being vigilant for predators). Using only one hemisphere to engage in
a task leaves the other hemisphere free to engage in other functions. This provides evidence for the
