Localisation of function in the brain Flashcards
Holistic theory replaced by localisation theory.
In the early 19th century holistic theory suggested that all parts of the brain were involved in processing thought and action.
AO1: Localisation of function
Specific areas of the brain were later linked with specific physical and psychological functions.
If an area of the brain is damaged through illness or injury, the function associated with that area is also affected.
The brain is lateralised and divided into 2 hemispheres.
What is laterisation?
AO1: Localisation of function
Laterisation describes some physical and psychological functions being controlled by a particular hemisphere.
Generally, the left side of the body is controlled by the right hemisphere and the right side of the body by the left hemisphere.
The cerebral cortex is the outer layer of the brain (both hemispheres).
The cerebral cortex of both hemispheres is divided into 4 centres called the lobes.
What is a lobe?
What lobes is the cerebral cortex divided into?
AO1: Localisation of function
A lobe is part of an organ that is separate in some way from the rest, with a specific function.
- Frontal,
- temporal (sides),
- parietal (top) and
- occipital (back).
Cerebral cortex divided into 4 lobes;
- Motor cortex
Where is it located?
What is its purpose?
What happens if it’s damaged?
AO1: Localisation of function
- Found at the back of the frontal lobe (of both hemispheres).
- Controls voluntary movement.
- Damage to motor area may cause loss of control over fine movements.
Cerebral cortex divided into 4 lobes;
- Somatosensory area
Where is it located?
What is its purpose?
What happens if it’s damaged?
AO1: Localisation of function
- At the front of the of the parietal lobes, separated from the motor area by a ‘valley’ called the central sulcus.
- Processes sensory information from the skin (touch, heat, pressure, etc.)
- The amount of somatosensory area deoted to a particular body part denotes its sensitivity.
Cerebral cortex divided into 4 lobes;
- Occipital lobe
Where is it located?
What is its purpose?
What happens if it’s damaged?
AO1: Localisation of function
- This is at the back of the brain (visual cortex).
- Each eye sends information from the right visual field to the left visual cortex, and from the left visual vield to the right visual cortex.
- Damage to either hemisphere can produce blindness in part of their assigned visual field of both eyes.
Cerebral cortex divided into 4 lobes;
- Auditory area
Where is it located?
What is its purpose?
What happens if it’s damaged?
AO1: Localisation of function
- In the temporal lobe.
- Analyses speech based information.
- Damage may produce partial hearing loss - the more extensive the damage, the more serious the loss.
Broca’s area, speech production.
Broca identified a small area in the left frontal lobe responsible for speech production.
Damage to this area causes ____
What is this characterised by and what difficulties may patients suffer?
AO1: Language centres
‘Broca’s aphasia.’
This characterised by speech that is slow, laborious and lacking in fluency.
People with this have difficulty with prepositions and conjunctions.
Broca’s most famous patient was ‘Tan’ - so called because that was the only word he could say.
Language centres; Wernicke’s area, language understanding.
Identified by Wernicke in the 1880s, it is responsible for langauge understanding, found in the ____
People with Wernicke’s aphasia produce language but ____
AO1: Language centres
‘left temporal lobe.’
Have problems understanding it, so they produce fluent but meaningless speech.
They will often produce nonsense words (neologisms) as part of the content of their speech.
A strength of localisation theory is support from neurosurgery.
Neurosurgery is used to treat mental disorders, e.g. cingulotomy involves isolating the cingulate gyrus - dysfunction of this area may be a cause of OCD.
What did Dougherty et al. study and find?
What did these this suggest?
AO3
Dougherty et al. (2002) studied 44 people with OCD who had a cingulotomy.
At follow-up, 30% met the crieria for successful response and 14% for partial response.
The success of such procedures strongly suggests that behaviours associated with serious mental disorders may be localised.
A strength of localisation theory is brain scan evidence to support it.
Petersen et al. (1988) used brain scans to show activity in Wernicke’s area during a listening task and in Broca’s area during a reading task.
What did Tulving et al. reveal?
What do these studies suggest?
A03
Also, a study of long-term memory by Tulving et al. (1994) revealed semantic and episodic memories are located in different parts of the prefrontal cortex.
There now exists a number of sophisticated and objective methods for measuring activity in the brain, providing sound scientific evidence if localisation of function.
A counterpoint to brain scan evidence used as support.
Lashley removed areas of the cortex (up to 50%) in rats learning the route through a maze.
Learning required ____
Suggesting?
AO3
‘all of the cortex rather than being confined to a particular area.’
This suggests that higher cognitive processes (e.g. learning) are not localised but distributed in a more holistic way in the brain.
A limitation is the language localisation model has been questioned.
Dick and Tremblay (2016) found that very few researchers still believe language is only in Broca’s area and Wernicke’s area.
Advanced techniques (e.g. fMRI) have identified regions in the ____
Suggesting?
A03
‘right hemisphere and the thalamus.’
This suggests that rather than being confined to a couple of key areas , language may be organised more holistically in the brain, which contradicts localisation theory.
Case study evidence.
Unique cases of neurological damage support localisation theory, e.g. Phineas Gage who lost some of his brain in an explosion and his personality changed.
However it is difficult to make meaningful generalisations based on a ____
Suggesting?
AO3
‘single individual and conclusions may depend on the subjective interpretation of the researcher.’
This suggests that some evidence supporting localisation may lack validity, oversimplifying brain processes, and undermining the theory.
