Biopsychology
Discuss what research has shown about localisation of function in the
brain [16 marks]
The localisation of function theory suggests that different areas of the brain are
responsible for specific functions, behaviours, and processes. This was discovered
by Broca and Wernicke, and contrasted earlier holistic theories which assumed all
parts of the brain were involved in behaviour. With localisation theory, if one specific
area of the brain is damaged, then the function in which they perform will also be
affected. The brain is split symmetrically in half into two hemispheres, right and left. It
has been suggested that certain psychological and physiological functions are
associated with a particular hemisphere. As well as this, it is known that the left
hemisphere controls the right side of the body and the right hemisphere controls the
left side of the body.
The outer layer of the hemisphere is known as the cerebral cortex, which is split into
four lobes known as the temporal lobe, the frontal lobe, the parietal lobe, and the
occipital lobe. Within the back of the frontal lobe is the motor area, which controls
voluntary movement of the body, leading to a loss of fine motor skills if damaged. In
the front of the parietal lobe is the somatosensory area, which represents sensory
information from the skin. The amount of area a body part has in the somatosensory
area denotes its sensitivity. The visual area is situated in the occipital lobe. Within
this, the eyes send information from the right visual field to the left visual cortex, and
vice versa. Due to this, damage can lead to blindness. Finally, the auditory area is
located in the temporal lobe, and it analyses speech based information. Damage to
this area can result in hearing loss.
Broca and Wernicke located two specific areas which were involved with language,
tying into localisation theory. Broca’s area is located in the left frontal lobe and is
related to speech production. If damaged, this can cause Broca’s aphasia which is
characterised by slow, inarticulate speech. On the other hand, Wernicke’s area is in
the left temporal lobe and is related to language understanding. If damaged, this can
cause Wernicke’s aphasia which is characterised by fluent but meaningless speech,
containing nonsense words.
One strength of localisation theory is that there is evidence linking damage of areas
in the brain to mental disorders. Neurosurgery is a last minute resort to treating
various mental disorders, such as a cingulotomy for OCD. In a study examining the
effectiveness of a cingulotomy in treating OCD, 30% of people met the criteria for a
successful surgery and response, with around 15% meeting the criteria for a partial
, successful response. This suggests that behaviour of those with mental disorders
can be linked to certain areas of the brain, and so supporting localisation theory.
However, one limitation is that brain function may not be localised to only Broca and
Wernicke’s areas. Advanced brain scanning techniques, such as fMRI, have shown
that language function is distributed more holistically rather than to specific areas.
Instead, function was identified across the cortex, the right hemisphere, and
subcortical regions. Therefore, this contradicts localisation theory as it suggests
language is organised holistically, and is not confined to one particular area. As a
scientific method has been used to reach this, the validity is increased.
On the other hand, another strength of localisation theory is that there is brain
scanning evidence supporting the localisation of brain function. Brain scanning
technology showed that Wernicke’s area was active during a listening task, whereas
Broca’s area was active during a reading task. Furthermore, studies showed that
semantic and episode memories reside in different parts of the cortex. As these are
used everyday, it suggests that everyday brain functions are localised more than
they are holistic. Therefore, this shows how objective methods have been utilised in
order to provide scientific evidence for the localisation of brain function.
A final limitation to consider is the evidence challenging localisation theory. In a study
examining the activity of brain areas of rats whilst trying to learn the route of a maze,
a researcher removed various cortex areas. The findings showed that no brain area
was more important than another. Instead, every part of the brain was used by the
rat whilst trying to learn. This research is valuable as it examines an everyday task of
learning, and that the brain works holistically during this. Thus suggesting that higher
cognitive processes are distributed holistically, rather than being localised.
Discuss research on hemispheric lateralisation [16 marks]
Hemispheric lateralisation is the assumption that the two hemispheres of the brain
are functionally different, and certain mental processes and behaviour are mainly
controlled by only one hemisphere. A common example for this is language, as it is
lateralise due to being performed by one hemisphere. Within this, the right
hemisphere is suggested to be the analyser, whilst the left hemisphere is suggested
to be the synthesiser.
However, some functions appear in both hemispheres, such as vision, motor, and
somatosensory. The motor area of the brain is contralaterally wired, which means
both hemispheres are involved in movement. In the case of vision, it is both
contralateral and ipsilateral, due to how the visual fields are connected to their
opposite hemispheres. The right visual field is connected to the left hemisphere, with
the left visual field being connected to the right hemisphere. This is beneficial as it
