Localisation of function in the brain

Question 1

Evidence supporting localised brain functions

Answer 1

Evidence supporting localised brain functions is provided by Broca (1865). He conducted a case study on Louis Leborgne, who was often referred to as ‘Tan’ because that was the only syllable that he could say despite being able to understand spoken language. A post-mortem examination found damage to an area of the left frontal lobe. This supports the localisation of a ‘language centre’ specialised for speech production which is known now as ‘Broca’s area’. Further evidence of LOF comes from support in the case study of Phineas Gage (1848) an accidental explosion during railroad construction shot a metal pole into his left cheek and through the top of his head damaging a significant part of his frontal lobe. As a result, Gage suffered drastic changes to his personality from someone who was calm to someone who was quick-tempered and rude. This supports the localisation of emotional control to the pre-frontal cortex of the frontal lobe.

Question 2

Evidence refuting localised brain functions

Answer 2

Evidence refuting localised brain functions is provided by Lashley (1950). He removed 10-50% of the cortex in rats that were learning a maze. He found that regardless of the area removed, rats could recover and relearn how to complete the task. This suggests areas of the cortex have equipotentiality – the ability of intact parts of the brain to perform functions lost by the destruction of other parts. Higher cognitive functions (e.g. those involved with learning) may therefore not be localised but distributed holistically throughout the brain.

Question 3

Beta bias in research into localisation of function.

Answer 3

Some psychologists argue that the idea of localisation of function fails to account for gender differences. Herasty (1997) found that women have proportionally larger Broca’s and Wernicke’s areas than men which can perhaps explain the greater ease of language use amongst women. This suggests a level of beta bias in the theory: the differences between men and women are ignored and variations in the size and activation of the areas used during various language activities are not considered. Therefore, caution should be made when generalising research findings into localisation of function between males and females equally as different brain structures/size.