Localisation of function in the brain

Lateralisation

The dominance of one hemisphere of the brain for particular physical and psychological functions

The limbic system

• controls our emotions

• located around the central core of the brain

• interconnected with hypothalamus

• contains hippocampus

• has key roles in memory

The central core

• regulates involuntary behaviours such as breathing, sleeping or sneezing

• regulates eating and drinking

• regulates endocrine system to maintain homeostasis

The cerebrum

• regulates higher intellectual processes

• made up of the left and right hemispheres

• hemispheres are connected by fibres called corpus callosum

Localisation

The theory that specific areas of the brain are associated with particular physical and psychological functions

What does the corpus callosum do?

Enables messages to enter the right hemisphere to be conveyed to the left hemisphere and vice versa

Broca’s area

An area of the frontal lobe of the brains 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

Evidence for Wernicke’s and Broca’s area

Peterson (1988) used brain scans to show how Wernicke’s area was active during a listening task and Broca’s area was active during a reading task, suggesting that these areas are responsible for these tasks

Neurosugical evidence for localisation

Neurosurgery is still used today for treatment resistant severe depressives and extreme cases of OCD. The success of these procedures strongly suggest that symptoms and behaviours associated with serious mental disorders are localised.

Case study evidence for localisation

• Gage after being impaled by an iron pole through his left cheek, passing behind his left eye, and exciting his brain and skull

• Survived but was left with a severe personality change

Caveat to localisation

• Higher cognitive functions are not localised.

• Lashley (1950) suggests that basic motor and sensory functions are localised, but not higher mental functions

• Lashley claimed that intact areas of the cortex could take over responsibility for specific cognitive functions following injury to the area normally responsible for that function

• According to this point of view, the effects of damage to the brain would be determined by the extent rather than the location of the damage

• This view is supported by the discovery that humans were able to regain some of their cognitive abilities following damage to specific areas of the brain