What is localisation of function?
● The theory that different areas of the brain are responsible for different behaviours,
processes or activities.
● The brain is divided into two hemispheres connected by the corpus collosum.
● It is believed that the left hemisphere is responsible for some of the cognitive functions such
as attention, processing of visual shapes and patterns, emotions, etc.
What are the 4 sub divisions?
- Frontal lobe – at the front of the brain, responsible for thinking and working memory
- Temporal lobe – on each side of the brain, by the ears, contains the auditory cortex and is
responsible for some forms of memory. - Parietal lobe – at the top of your head, behind the frontal lobe, responsible for balance,
pain, temperature etc. - Occipital lobe – located at the back of the brain, contains the visual cortex.
Describe the localisation in each lobe
There is further localisation within each lobe, as research shows that very specific areas of the brain
can be responsible for specific functions. These include:
● The Motor area - A region of the posterior part of the frontal lobe involved in regulating
movement.
● The Somatosensory area - An area of the parietal lobe that processes sensory information
such as touch.
● Broca’s area – located in the posterior part of frontal lobe of the brain in the left
hemisphere (in most people) responsible for speech production.
● Wernicke’s area - An area of the temporal lobe in the left hemisphere (in most people)
responsible for language comprehension.
A03 - Research
- Initial research by Paul Broca and Carl Wernicke discovered that the language centres of
the brain are predominantly focused on the left hemisphere. The Broca’s area, cited as being responsible for speech production is located in the posterior part of the PFC and the Wenicke’s area, cited as being responsible for speech comprehension, is located in the
temporal lobe. - The initial findings are supported by more recent research Petersen et al. (1988) who used
fMRi brain scans to demonstrate how Wernicke’s area was active during a listening task and Broca’s area was active during a reading task, suggesting that these areas of the brain have different functions. - However, research into cortical remapping from researchers such as, Grafman (2000) indicates that following brain trauma/injury homologous areas of the brain near to the injury or on the opposite hemisphere can adopt the function of areas such as Broca’s or
Wernicke’s. - Therefore, whilst function may be initially tied to one location, the brain is a continually adapting and changing organ.
A03 - Lashleys research
- The Lashley’s (1950) study of rats suggests that higher cognitive functions, such as the processes involved in learning, are not localised but distributed in a more holistic way in the brain.
- Lashley removed areas of the cortex in rats that were learning a maze. No area was proven to be more important than any other area in terms of the rats’ ability to learn the maze. The process of learning appeared to require every part of the cortex, rather than being confined to a particular area.
- This research suggests that whilst it may be possible to pinpoint some functionality to
specific areas, higher order processing may require multiple regions of the brain to be
synthesised. One issue with Lashley’s work was that it was conducted using animals (rats). - Therefore, whilst this animal research is insightful, one must be cautious in applying the findings of such a complex research area, to brain localisation and function in humans.
A03 - Hubel and Wiesel animal studies
- Animal research questions the rigidity of localisation of function
- Hubel and Wiesel (1963) conducted a study which involved sewing one eye of a kitten shut and analysing the brain’s cortical responses. It was found that the area of the visual cortex associated with the shut eye was not idle (as had been predicted) but continued to process
information from the open eye. - These research findings further indicate that whilst localisation of function exists, the brain is adaptable and has plasticity, which means it adapts and changes according to circumstance and trauma.
- However, similar to Lashley’s research finding, we should be cautious when generalising
Hubel and Wiesel’s findings of localisation in animals (cats) to human beings.
