Localisation

Question 1

What is localisation?

Answer 1

Localisation of function is the theory that specific parts of the brain are responsible for specific behaviours or cognitive processes.

Question 2

What is strict localisation?

Answer 2

The idea that specific areas of the brain correspond to certain psychological functions, and that these functions can be clearly mapped onto the brain.

Question 3

What is weak/relative localisation?

Answer 3

The idea that one brain area may be responsible for a function, but not exclusively, and other areas may also take over the function.

Question 4

Research supporting strict localisation: Broca (1861)

Answer 4

1. Paul Broca (1861) conducted a longitudinal study on a patient that was experiencing a form of aphasia due to the lesion found throughout his left frontal lobe. Subsequently to performing a post-mortem autopsy, Broca found destructive lesions in the second and third frontal convolutions of the left cerebral hemisphere, the inferior margins of the Sylvian fissure, the insula and the adjacent part of the striatum, confirming his ideas about the location of language. The specific frontal lobe region was later defined as Broca’s area, and the aphasia was given the name Broca’s aphasia— the loss of articulated speech.

Question 5

Research supporting strict localisation: Wernicke (1874)

Answer 5

Pertaining to the findings of Wernicke’s (1874) study on the localisation of function in patients with brain damage, it was concluded that the area located throughout the temporal lobe of the dominant hemisphere was responsible for the comprehension of written and spoken language. This area was latterly characterised as the ‘Wernicke’s area’.

-It was found that individuals with Wernike aphasia have a general impairment of language comprehension, while at the same time speech production is intact. As a result, when they speak they sound really fluent and natural, however, the words recite are meaningless.

Question 6

Research opposing strict localisation: Karl Lashley (1890-1958)

Answer 6

Karl Lashley (1890-1958), student of Franz, was the American neuropsychologist who was most influential in his arguments against behaviourism. Lashley (Brain Mechanisms and Intelligence, 1929) argued that higher cognitive processes were not localised but distributed. BMI described studies with rats and mazes. Lashley removed portions of the cerebral cortex, varying from 10%-50% in an effort to study the role the cerebral cortex played in learning.

Karl Lashley Introduced two principles:

Principle of mass action: Based on the observation that the amount of cortex removed was critical to the learning abilities of the rats, Lashley concluded that the efficiency of learning, and generally that of higher cognitive abilities, is a function of the intact mass of the cortex. More tissue => more learning available

Equipotentiality: All areas of the cortex are equally important to learning - no area was proven to be more important than any other area. Also found evidence that brain regions can take on different functions as needed (Plasticity).

Question 7

State the difference between lateralisation and localisation:

Answer 7

The lateralisation of brain function is the tendency for some neural functions or cognitive processes to be specialised to one side of the brain or the other.

Localisation refers to how different human cognitive abilities and behaviours are localised in specific parts of the brain.

Question 8

Discuss the split-brain study conducted by Sperry (1968)

Answer 8

Split-brain is a type of disconnection syndrome when the corpus callosum connecting the two hemispheres of the brain is severed to some degree. It is an association of symptoms produced by disruption of, or interference with, the connection between the hemispheres of the brain. The surgical operation to produce this condition (corpus callosotomy) involves transection of the corpus callosum, and is usually a last resort to treat refractory epilepsy.

According to research pioneered by Sperry (1968), epileptic patients partook in several hemisphere-related tasks that inferred whether a particular side was favoured. The findings showed that:

• Laterisation of function include the assertion that the right half of the brain is dominant for visuo-spatial ability (demonstrated in tasks like reading maps or recognising faces), as well as musical abilities and understanding intonation in speech.
• The left half of the brain seems to be more positive than the right and is dominant for language and logical or mathematical abilities