Localisation of Function in the Brain

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Localisation of function- the theory that different areas of the brain are responsible for different behaviours, processes or activities.

Broca and Wernicke discovered that specific areas of the brain are associated with particular physical and psychological functions. Before this scientists generally supported the holistic theory of the brain- that all parts of the brain were involved in the processing of thought and action.

P- there is supporting evidence for the localisation theory.

E- Phineas Gage survived a metre-length pole passing through his left cheek, left eye and exiting his skull. The damage to his frontal lobe left a mark on his personality – he turned from a calm reserved person to someone who was quick-tempered and rude.

E- This suggests that the frontal lobe may be responsible for regulating mood, supporting localisation theory.

L- However, as this is a case study, it cannot provide particularly strong support for localisation theory as it lacks external validity in that Gage may be a unique case.

 HEMISPHERES OF THE BRAIN AND THE CEREBRAL CORTEX:

• The brain is divided into 2 symmetrical halves called left and right hemispheres.
• Some of our  physical and psychological functions are controlled or dominated by a particular hemisphere- also known as lateralisation.
• Activity on the left-hand side of the body is controlled by the right hemisphere and activity on the right-hand side is controlled by the left hemisphere.
• The cerebral cortex is 3mm thick and covers the inner parts of the brain. The human cortex is much more developed than other animals.

P-  there is undermining evidence for localisation of function.

E- Lashley removed areas of the cortex (10-50%) 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.

E- The process of learning appeared to require every part of the cortex, rather than being confined to one particular area. This seems to suggest that learning is too complex to be localised, and requires the involvement of the whole of the brain. Therefore, processes involved in learning may be distributed in a more holistic way in the brain.

L- However, we should be cautious in drawing conclusions related to human learning from this study as the participants were rats and therefore they may learn (and their brains may be localised) differently to humans.

Motor Cortex: Responsible for generation of voluntary motor movement.

Located in both hemispheres in frontal lobe, along region known as precentral gyrus (just in front of central sulcus which divides frontal and parietal lobes) 

Each side controls opposing movement on other body side.

Different parts control different parts of body. Parts are arranged logically next to one another.

Damage to area may result in loss of control over fine motor movement.

P- There is evidence to contradict the localisation theory.

E- When the brain has become damaged (e.g. illness, accident), and a particular function has been compromised or lost, the rest of the brain appears…