This document contains a curated collection of essay plans focused on biopsychology, offering A-level psychology students a comprehensive resource. Explore the intricate relationship between the brain, biology, and behaviour through concise outlines of key topics, theories, and research studies.
The holistic theory suggests that all parts of the brain are involved in
processing thoughts and behaviour. This was replaced by the localisation
of function theory, which suggests that specific areas of the brain are
responsible for specific functions. The brain is divided into two
hemispheres – the left and right hemisphere. Lateralisation is the idea
that some functions are controlled by a specific hemisphere. The outer
layer of the brain is the cerebral cortex, where higher cognitive functions
take place. The cerebral cortex of both hemispheres is divided into four
lobes – the frontal, occipital, temporal and parietal lobes. Within these,
there are four areas of the brain – the motor area (controls voluntary
movement), the somatosensory area (processes information from the skin
about pressure and pain), the visual area (information from the eyes
processes what is seen) and the auditory area (analyses speech and
sound). Furthermore, Broca’s area, in the left frontal lobe, is responsible
for speech production. Damage to Broca’s area causes Broca’s aphasia
which leads to slow speech or difficulty finding words. Wernicke’s area is
in the left temporal lobe and is responsible for speech comprehension.
Damage t this area causes Wernicke’s aphasia, such as not understanding
speech.
A strength of the localisation theory is that there is supporting evidence
from neurosurgery. Neurosurgery is used to treat mental disorders by
performing surgery on areas of the brain. Research has found that 44
people with OCD had a particular type of brain surgery, and 30% had a
successful response. This shows how surgery to a particular area of the
brain can influence behaviour. This consequently adds validity to the
theory that specific functions are localised in specific areas of the brain.
Another strength of the theory is that there is support from studies of
patients with aphasia due to lesions. Broca researched 9 patients with
similar speech deficits and found that they all had lesions in a particular
part of their left frontal lobe. In addition, Wernicke researched patients
who could still speak but had problems understanding language. He found
they all had similar lesions in a similar area in the left temporal lobe. This
shows that there are specific areas in the brain that are specialised for
language production and comprehension.
However, a limitation of these studies is that lesions often affect several
brain areas. Drokners et al. examined the preserved brains of 2 of Broca’s
patients and found that other areas were damaged, not just Broca’s area.
In reality, lesions that only affected Broca’s area generally only result in
temporary speech disruption. This suggests that language involves
networks of brain regions rather than just specific areas.
, Nevertheless, a final strength of localisation theory is that there is brain
scanning evidence to support it. Petersen et al. used brain scans to
demonstrate activity in Wernicke’s area during a listening task, and
Broca’s area during a reading task. This shows how different functions are
located in different parts of the brain. It adds scientific credibility to
localisation theory as the research techniques, the brain scans, are
objective and reliable.
Hemispheric lateralisation + split brain research (16)
Hemispheric lateralisation means that the brain is split into 2
hemispheres. Some functions are localised and appear in both left and
right hemispheres, such as auditory, visual, motor and somatosensory
areas. However, for most people, language appears to be lateralised in
the left hemisphere (Broca’s and Wernicke’s area). The brain is
contralateral – the right hemisphere controls the left side of the body and
the left hemisphere controls the right side of the body. Each eye has a left
and right visual field – the left visual field is connected to the right
hemisphere and the right visual field is connected to the left hemisphere –
this gives visual areas different perspectives and more depth. Sperry
(1968) conducted research into split-brain patients. 11 patients who had
their corpus callosum severed to treat epilepsy were used to explore the
functions of the brain separately. He used specialised equipment to
present a word or image to the left or right visual field. The participants
had to either describe what they say, draw it or select an object that best
resembled it from behind a screen. When an object was shown to the right
visual field, they could describe it, as language is lateralised to the left
hemisphere. However, when an object was shown in their left visual field,
they couldn’t name it (as language is not lateralised to the right
hemisphere) but they could select an object or draw it with their left hand.
This study shows how the left hemisphere is more verbal, while the right
hemisphere is more creative and emotional.
A strength of hemispheric lateralisation is that there is evidence for
lateralised brain functions in ‘normal’ brains. PET scans show that the
right hemisphere is more active in normal participants, when they look at
global elements of an image, and the left hemisphere is more active when
looking at finer detail. This suggests that hemispheric lateralisation is a
feature of neurotypical as well as split brains. Therefore, this adds validity
to the theory of hemispheric lateralisation.
However, a limitation of the theory is that the idea that the hemispheres
have separate functions may be wrong. Nielsen et al. analysed 1000 brain
scans and found that people did use certain hemispheres for certain tasks,
but there was no dominance. There might be different functions in the left
hemisphere and right hemisphere, but research suggests that people
don’t actually have a dominant side. This means that the idea that people
are either left brained or right brained is wrong.
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