AQA A-Level Psychology Biopsychology – 16 mark essays
Hemispheric lateralisation
AO1 – outline:
Hemispheric lateralisation refers to the idea that the two halves of the brain are functionally
different. Language, for example, is lateralised because it is controlled by the left hemisphere. It is
also localised because speech production is located in Broca’s area (in the frontal lobe) and language
understanding is processed by Wernicke’s area (in the temporal lobe). Movement of the two halves
of the body is also lateralised, as the left hemisphere controls the motor skills of our right side, and
the right hemisphere controls the left side of our body. In this way, movement is contralateral; as is
vision. Split-brain research by Roger Sperry has demonstrated that objects in our left visual field are
sent to the right hemisphere, and vice versa. Information is then passed between the two
hemispheres through a bundle of nerves called the corpus callosum.
AO3 – evaluate:
One strength of research into hemispheric lateralisation is that it has lots of support. Fink et al. used
PET scans to observe lateralisation on connected-brain participants who were shown a series of
images. When asked to focus on the global elements of an image (such as the whole forest), the
right hemisphere was the most active. By contrast, participants who were told to focus on specific
details (such as individual trees) exhibited greater activity in their left hemisphere. This supports the
theory of lateralisation by suggesting that the brain does not process information holistically, but in
separate regions based on the nature of the stimuli, and is thus consistent with the symptoms
displayed by Robert.
However, one limitation of hemispheric lateralisation research is that it may have falsely
perpetuated the myth of the left hemisphere as ‘analyser’ and the right hemisphere as ‘synthe siser’.
Jared Nielsen analysed brain scans from 1000 people aged 7 to 29 years and found evidence for
lateralisation, but no evidence for a dominant side. This contradicts the popular belief that creative,
artistic, free-thinking people are ‘right-brained’ and analytical, logical and orderly people are ‘left-
brained’. Thus, hemispheric lateralisation may be a credible theory, but it does not manifest itself -
in reality - in the way that is commonly believed. This means that the initial claims of the explanation
now lack support and offer little contribution to our understanding of cases such as Robert’s.
One of the main advantages of hemispheric lateralisation is that it increases neural processing
capacity (i.e. the ability to multitask). Rogers et al. (2004) found that domestic chickens with
lateralised brains had 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 is important because it provides evidence for the
advantages of brain lateralisation and demonstrates how it can enhance brain efficiency in cognitive
tasks.
Localisation of function
AO1 – outline:
Localisation of function refers to the theory that certain functions have certain locations in the brain.
For example, the motor cortex - found in the frontal lobe of the brain - coordinates voluntary
movement. The somatosensory cortex, found in the parietal lobe, processes sensory information.
, The occipital lobe (towards the back of the brain) deals with visual information while the temporal
lobe processes auditory information. Within the temporal lobe resides Wernicke’s area, which Carl
Wernicke demonstrated is responsible for language understanding. Damage to Wernicke’s area
leads to Wernicke’s aphasia. Sufferers can speak fluently, but they do so in neologisms (nonsense
words, or words arranged in an order that doesn’t make sense). The frontal lobe houses Broca’s
area, which was discovered by Paul Broca and identified as responsible for speech production.
People with Broca’s aphasia due to damage to the frontal lobe have difficulty forming fluent speech
and may speak very slowly and laboriously, often without use of prepositions. Broca’ s most famous
patient was Patient Tan, named as such because they could only say the word ‘Tan’. Basic
neuroanatomical organisation - hemispheric lateralisation and contralateral organisation. Left
hemisphere controls language while the right hemisphere excels at visual and motor tasks.
AO3 – evaluate:
In terms of evaluation, localisation of function has been supported by surgical procedures, such as
cingulotomies, which remove a part of the brain associated with OCD. Darin Dougherty et al.
followed up patients 32 weeks after they had undergone a cingulotomy for OCD and found 30% had
made a full recovery, while 14% had made a partial recovery. This suggests that the symptoms of a
disorder may be isolated to a single region of the brain, since targeted re moval can prove beneficial.
There is further research support to lend credibility to the theory of localisation of function.
Petersen et al. scanned the brains of patients while they were presented with a series of stimuli.
They found that Broca’s area was the most active during reading tasks and Wernicke’s area was the
most active during listening tasks. This is consistent with the idea that each part of the brain
performs a specific function in relation to language processing and understanding. In a separate
study, Peterson and Buckner found that episodic and semantic memories are stored in different
parts of the brain. Episodic memories are housed in the hippocampus and semantic memories are
found in the temporal lobes.This makes sense in the context of patient HM, who had parts of his
temporal lobes removed to reduce his epileptic seizures, suffering severe amnesia as a result. Again,
this supports the theory that brain functions are localised.
However, research by Dick and Tremblay (2016) suggests that the localisation of function theory may
oversimplify the reality of the complexity of the brain. They found that, in fact, only 2% of modern
researchers believe that functions are entirely localised. Recent research has even suggested that
there are language streams in the right hemisphere of the brain, contradicting the idea that
language is localised to specific areas of the left hemisphere only. Furthermore, functional recovery
research shows that - via axonal sprouting and the recruitment of homologous areas of the brain on
the opposite side - we can grow new neural pathways to replace damaged ones. Therefore,
suggesting localisation is more flexible than first thought since the brain is so highly adaptive (known
as neural plasticity).
One famous case study that highlights localisation of function is that of Phineas Gage, a railway
worker who suffered an iron bar going through his skull. Although he survived, his personality
drastically changed e.g. loss of inhibition and anger. Localisation of function of personality. However
case studies such as this may not be generalisable due to their individualised nature .
Methods of studying the brain
AO1 – outline:
There are four methods of studying the brain: electroencephalogram (EEG), event-related potentials
(ERPs), functional magnetic resonance imaging (fMRI) and post mortem examination. EEGs involve
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