LOCALISATION OF BRAIN FUNCTION

• What is localisation of brain function?


  The idea that certain function e.g. language, memory have certain locations or areas within the brain.

  This has been supported by recent neuroimaging studies, but was also examined much earlier, typically using case studies.
• What is the motor area?

  Located in the frontal lobe and is responsible for voluntary movements by sending signals to the muscles on the body.

  -Regions are arranged in logical order.
• Hitzig and Frisch (1870) - discovered that different muscles in the body are coordinated by different areas of the motor cortex by electrically stimulating the motor areas of dogs.

  -Results in muscular contractions in different areas of the body depending on where the probe was inserted.
• What is the somatosensory area?

  Located in the parietal lobe and receive incoming sensory information from the spine to produce sensations related to e.g. pressure, temperature.

  -Different parts of the area receive messages from different locations in the body.
• Robertson (1995) - Found that the area of the brain is highly adaptable e.g. braille readers have larger areas on the somatosensory area for their fingertips.
• What is the visual area?

  Found at the back of the brain in the occipital lobe , which receives and processes information.

  -Contains different parts that process different types of information e.g. colour, shape.

  -Information from the right hand side visual field is processed in the left hemisphere, and vice versa.
• What is the auditory area?


  Located in the temporal lobe and is responsible for analysing and processing acoustic information.

  -Contains different parts and the primary auditory area is involved in processing simple features of sound e.g. volume, pitch.

  -Information from the left ear goes primarily into the right hemisphere and vice versa.
• What is Broca's area?

  Named after Paul Broca, who discovered this region while treating a patient called Tan.

  -Tan could understand spoken language but was unable to produce any coherent words and could only say Tan.

  -After Tans death, Broca conducted a post mortem examination and discovered he had a lesion in his left frontal lobe - led Broca to conclude that the area was responsible for speech production.

  -People with damage to this area experience Broca's aphasia - results in slow and inarticulate speech.
• What is Wernicke's area?

  Found in the left temporal lobe and is involved in language processing/comprehension.

  -People with damage to this area struggle to comprehend language, nut can still produce sentences (Wernicke's aphasia).

  -Wernicke concluded that language involves a separate motor and sensory region.
• • Motor region - Broca's area
  • Sensory region- Wernicke's area.
• What is a weakness of localisation of brain function?

  Equipotentiality theory - the claim that functions are localised to certain areas of the brain has been criticised.

  Lashely - removed areas of the cortex in rats - no one area appeared to be more important.

  -Because the brain is so complex that not one part acts independently from the rest, so strict localisation is impossible

  -Biologically reductionist.

  -More important to investigate how they communicate with each other.
• What is a weakness of localisation of brain function?

  Biologically reductionist - Wernicke claimed that areas of the brain are independent but they must interact with each other in order to function.

  Damage to the connection between any two points can result in impairments that resemble damage to the localised brain region associated with that function.

  -Reduces the credibility of the theory.

  E.g. Dejerner - interactions between different areas produce complex behaviour e.g. language.
• What is a weakness of the localisation of brain function?

  Individual differences and beta bias - Herasty (1997) - women have larger Broca and Wernicke's areas than men - been observed through scanning techniques.

  -Suggests all men and women are the same - beta bias

  -Cannot apply ideas equally to men and women

  -Further research is needed.
• What is a strength of localisation of brain function?

  Evidence through case studies and scans - patient Tan had left frontal temporal lobe degeneration in the Broca area causing non fluent aphasia.

  Close to the motor region- controls mouth

  Damage causes motor aphasia; trouble with speech production and consists of short sentences.

  -Reading/writing not as affected

  Scanning techniques have shown damage to Broca's area in patients with motor aphasia.
• What is a weakness of localisation of brain function?

  Dronkers et al (2007) - conducted an MRI scan on Tan's brain to try and find Broca's findings. Although there may have been a lesion in Broca's area, they also found evidence suggesting other areas may have contributed to the failure in speech production.

  -This suggests that Broca's area may not be the only region responsible for speech production and the deficits found in patients with Broca's aphasia could be the result of damage to other neighbouring regions.