Localisation of Function of the Brain

Holism Theory - the historical view that all areas of the brain worked together to process thought and complete actions

Phrenology - proposed by Gall; the idea that bumps in areas of the skull reflect personalities - localisation

Localisation of Function - the theory that different areas of the brain are responsible for different behaviours, processes and activities

Lateralisation of Hemispheres - the theory that (of the 2 hemispheres) one hemisphere controls the functions of the opposite side of the body

Broca and Wernicke - discovered that specific areas of the brain are associated with specific physical and psychological functions, in the 19th century

Cortical Specialisation - another name for Localisation of Function

Cerebral Cortex

• outer layer of both hemispheres
• thin cover over the brain
• higher mental functions such as language
• referred to as 'grey matter' due to its appearance caused by the positioning of the neurons' cell bodies
• divided into 4 sub-lobes, each associated with different functions
  • frontal lobe
  • occipital lobe
  • temporal lobe
  • parietal lobe

Motor Area

• back of the frontal lobe
• controls voluntary movement
• damage could result in loss of control over fine movements
• includes Broca's Area

Somatosensory Area

• front of the parietal lobes
• separated from the motor region by Central Sulcus
• information is sent from the skin receptors (touch, pain, temperature, pressure)
• receives all of the sensory input from the body and processes it into sensations
• transported by neurons to the brain
• the amount of somatosensory area dedicated to a specific body part is proportionate to that body part's sensitivity (our hands and face occupy over half of the somatosensory area)

Visual Area

• occipital lobe
• back of the cerebral cortex (smallest lobe)
• eye sends info from one visual field to the opposite visual cortex
• damage could produce blindness

Auditory Area 

• temporal lobe
• front, bottom of the cerebral cortex
• analyses speed-based information
• speech comprehension
• damage may produce hearing loss
• includes Wernicke's Area

Language is restricted to the left side of the brain

Broca

• Broca, a surgeon, identified a small area in the frontal lobe that was responsible for speech production in the 1880s
• motor area (language production)
• damage to the area leads to Broca's aphasia
  • slow, laborous and non-fluent speech
  • Broca's patient 'Tan' could only say the word Tan

Wernicke

• studied patients who had a speech production problem, but could not recognise they had it themselves
• Wernicke's Area is in the left temporal lobe
• responsible for language comprehension
• leads to Wernicke's aphasia when damaged
• produce nonsense words (neologisms) as part of the content of their speech

P - Peterson did brain scans on the different areas of the brain
E - Wernicke's area was active during a listening task and Broca's during a reading task
E - Wernicke's is for speech comprehension and Broca's is for speech production (verbalisation)
L - scientific external application for localisation

P - Tulving did PET brain scans on left and right hemisphere
E - found that right side lit up during episodic tasks and the left side suring semantic tasks
E - supports localisation of the brain
L - scientific external application

P - Dougherty did lobotmies on 44 OCD patients
E - found success in 1/3 of patients and a further postitive results in 14%
E - specific areas of the brain affect mental processes
L - neurological evidence for localisation

P - Phineas Cage was preparing explosives on tracks; a metal pole blasted into his left cheek
E - pole took out much of his left frontal lobe, and he became blinded, short tempered and rude
E - frontal lobe is responsible for processing and regulating mood
L - supports that damage to specific areas leads to specific physical and psychological damage

P - Lashley did lobotomy research
E - removed between 10% and 50% of rats' brains and the rats then had to learn a maze route
E - found that there was no partiulcar area that hindered learning the maze
L - tackles locatisation of function

P - theory of plasticity 
E - brain can change and mould depending on the situation which can lead to full recovery (e.g stroke victims)
E - Lashley's law of equipotentiality - brain circuits can replace lost neurological functions
L - challenges idea of localisation with alternative theory and external evidence