Localisation of function in the brain Flashcards
What is localisation of function?
Specific functions (physical and psychological) have specific locations in the brain
What are the 4 lobes which make up the brain?
Occipital, temporal, parietal, frontal
What are the 6 specialised areas in the brain?
Motor, somatosensory, visual, auditory, Broca’s, Wernicke’s
What is a case study which shows support for localisation of the brain?
Phineas Gage
How does Phineas Gage show support for localisation of function in the brain?
The change in his personality and temperament following the accident suggests that part of the brain that is responsible for regulating temperament is in the frontal lobe
What is the location and function of Moter?
Locaction: Back of frontal lobe
Function: Controls voluntary movement in the opposite side of the body
What is the location and function of Somatosensory?
Locaction: Parietal lobe
Function: Processes sensory information related to touch, pressure, pain and temperature which i then localises to specific body regions
What is the location and function of visual?
Locaction: the occipital lobe
Function: each eye sends information from the right visual field to the left visual cortex and the left visual field to the right visual cortex
What is the location and function of Auditory?
Locaction: Temporal lobe
Function: Analyses speech-based information
What is the location and function of Broca’s?
Locaction: Frontal lobe in the left hemisphere
Function: Responsible for speech function
What is the location and function of Wernicke’s
Locaction: Temporal lobe in the left hemisphere
Function: Responsible for speech comprehension
What are the three strengths for localisation of function in the brain?
Brain scan evidence of localisation- Petersen et al. (1988) used brain scans to demonstrate how Wernicke’s area was active during a listening task and Broca’s area was active during a reading task, suggesting that these areas of the brain have different functions.
Plenty of objective methods for measuring activity in the brain provides sound scientific evidence of localisation of brain function.
Case study evidence of localisation- The case study of Phineas Gage: Whilst working on the railroad in 1848, 25-year-old Phineas Gage was preparing to blast a section of rock with explosives to create a new railway line. During the process, Gage dropped his tamping iron onto the rock causing the explosive to ignite. The explosion hurled the metre-length pole through Gage’s left cheek, passing behind his left eye, and exiting his skull from the top of his head taking a portion of his brain with at - most of his left frontal lobe Incredibly, Gage survived but the damage to his brain had left a mark on his personality - by all accounts he had turned from someone who was calm and reserved to someone who was quick-tempered rude and no longer Gage. Gage is seen as a landmark case in science as the change in his temperament following the accident suggested that the frontal lobe may be responsible for regulating mood.
Counter- This is a case study and is unique to the individual. As a result it is hard to draw general conclusions from these results as it may not be the case for everyone.
Support for language centres from aphasia studies- There has been evidence which has revealed that damage to either Broca’s or Wernicke’s area has led to different types of language difficulty (aphasia).
Expressive aphasia (Broca’s aphasia)= an impaired ability to produce language. In most cases caused by brain damage in Broca’s area. E.g. Patient Tan. Paul Broca treated a man who could understand speech but couldn’t produce any coherent words (could only say the word ‘Tan’). When he died a post-mortem revealed that Tan had a lesion in the left frontal lobe= area responsible for speech production.
Receptive aphasia (Wernicke’s aphasia)= an impaired ability to understand language- usually the result of damage in Wernicke’s area. This suggests that the role of speech production and speech comprehension is localised in the brain.
Counter- Dronkers et al. (2007)- MRI of 2 Broca’s patients- found other areas other than Broca’s area which had been damaged suggests that language and cognition are far more complicated and involve networks of brain regions rather than being localised to specific areas.
What are the two limitations of localisation of brain function?
Law of equipotentiality- It has been found that when the brain is damaged and a function is lost, the rest of the brain can reorganise itself in an attempt to recover the lost function.
Lashley described this as the law of equipotentiality= surviving brain circuits ‘chip in’ so the same neurological action can be achieved.
E.g. there are a few cases of stroke victims being able to recover abilities that were lost as a result of the stroke.
Evidence for holistic theory- Lashley (1950)- suggested that higher cognitive functions, are not localised but distributed in a more holistic way in the brain.
He removed areas of the cortex (between 10 and 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. The process of learning appeared to require every part of the cortex, rather than being confined to a particular area.
This evidence seems to suggest that learning is too complex to be localised and requires the involvement of the whole brain.
