Localisation of brain function

• Localisation is the theory that specific brain areas are associated with their own specific brain function
• Localisation states that if an area of the brain is damaged so is the function associated with it
• Prior to the 19th century studies of the brain followed a holistic theory in which it was assumed that all parts of the brain were involved in all psychological functioning
• 4 brain lobes; frontal, parietal, temporal, and occipital
• the frontal lobe is responsible for higher level function such as thinking and logic
• The parietal lobe is responsible for spatial awareness and touch based sensory processing
• The temporal lobe is responsible for processing acoustic information
• The occipital lobe is responsible for processing visual information
• Broca's area is located in the bottom of the frontal lobe in the left hemisphere and is responsible for speech production
• When Broca's area is damaged it causes Broca's aphasia which is associated with slow, laboured speaking and difficulty using conjunctions in language
• Wernicke's area is located in the left temporal lobe and is responsible for language comprehension
• When Wernicke's area is damaged it causes Wernicke's aphasia which is characterised by neologisms (nonsense sentences) as words can still be produced but not understood
• The motor area is located in the back of the frontal lobe in both hemispheres
• damage to the motor area leads to loss of control over fine movements
• The somatosensory area is located at the front of the parietal lobe in both hemispheres
• The somatosensory area is separated from the motor area by the central suculus
• the somatosensory area processes touch related sensory information
• The amount of the somatosensory area dedicated to a particular body part determines how sensitive it is
• The visual area takes up the entirety of the occipital lobe
• Each eye sends information from the right visual field to the left visual cortex and vice versa
• Damage to the right side of the visual area causes issues with the left visual field and vice versa
• the auditory area is located in the temporal lobe
• Localisation strength; Case study of Phineas Gage supports this as after an accident he experienced a huge change in temperament becoming aggressive and short tempered following an injury to his frontal lobe supporting localisation as no other internal mental processes were impacted; HOWEVER case studies are rejected by a nomothetic approach for not being scientific as they cannot be easily generalised to create general laws of psychology as they only look into extremely rare cases
• Localisation weakness; conflicting studies as Lashley (1950) found that removing different areas of the cortex in rats did not impact their ability to learn a maze showing no brain area as more influential than another in learning suggesting a holistic theory; HOWEVER this study has severe ethical and extrapolation issues
• Localisation weakness; Biologically reductionist as it reduces complex brain functions that may use multiple areas of the brain at once to one simple function suggesting it does not provide enough understanding of the brain HOWEVER many psychologists favour this as it offers a simple level of scientific explanation that can be studied further to be expanded upon by later research
• Localisation weakness; theory of plasticity goes against this as it states when one brain area is damaged another can take over for it showing that other brain areas can carry out specific functions
• Localisation strength; Research support from Broca's patient Tan who was examined using post mortem examination and found that issues with speech production in his life was due to a damaged Broca's area; however there are many issues with post mortem examination including ethical issues as well as low temporal and spatial resolution