Discuss localisation of function in the human brain

Question 1

outline

Answer 1

Localisation of function is the argument that the capacity to carry out different functions or abilities is localised in particular areas of in the cerebral cortex.

Each hemisphere in the brain is sub-divided into four lobes, which are used to identify the location of brain structures and functions.

motor area is responsible for the planning and execution of voluntary motor movement and the brain sends signals to all the skeletal muscles in the body.
- motor area on one side of the brain controls the muscles on the opposite side of the body (contralateral representation) and is located in the frontal lobe, anterior to the central sulcus.

The somatosensory area is responsible for skin sensation (touch, pressure etc) and information is processed through upside-up contralateral representation.
- It is located in the parietal lobe.

The auditory area is responsible for auditory perception; it receives input via the auditory nerve and the thalamus.
- It is located in the temporal lobe.

The visual area is responsible for visual perception and is located in the occipital lobe.

Broca’s area is responsible for the production of spoken language, it contains the plans for motor movement required to speak each word.
- Instructions are passed from the area to the motor area, enabling movement of the muscles of the mouth and larynx when we want to speak.
- It is located in the left frontal lobe.

Wernicke’s area is responsible for the comprehension of spoken language as it contains a store of the sounds of words required to understand speech.
- Information is received from the auditory area when we hear language, before it is passed to the Wernicke’s area for comprehension.
- It is located in the left temporal lobe.

Question 2

limit 1

Answer 2

A weakness of localisation of function is that it has been challenged by contradicting research evidence.

Dronkers et al., (2007) re-examined the preserved brains of two Broca’s aphasic patients using high-resolution MRI imaging and found that other areas of the brain besides the Broca’s area were also damaged.

This suggests that language production is far more complicated than once thought and involves networks of brain regions rather than being isolated to one area, challenging the concept of localisation of function.

Question 3

limit 2

Answer 3

The concept of localisation of function has been further challenged by Joseph Dejerine (1892) who described a case in which the loss of an ability to read resulted from damage to the connection between the visual cortex and Wernicke’s area.

This suggests that complex behaviours, like reading, involve connections between different regions and are not isolated to one specific area.

This ultimately challenges the concept of absolute localisation of function.

Question 4

strength

Answer 4

A strength of localisation of function is that it has strong supporting evidence.

This is when an issue or debate is supported because of strong or convincing evidence.

For example, Paul Broca identified Broca’s aphasia in patient ‘Tan’ who could comprehend language but had significantly impaired speech production.

After he died, a post-mortem revealed damage to his left frontal lobe, now named Broca’s area.

This suggests our language centre for speech production is localised to one specific area, as localisation of function would predict.