Localisation Of Function In The Brain Flashcards
Holistic Theory Replaced By Localisation Theory
-In the early 19th centruy, holistic theory suggested that al parts of the brain were involved in processing thought and action.
-Specific areas of the brain were later linked with specific physical and psychological functions (localisation theory)
-If an area of the brain is damaged through illness or injury, the function associated with that area is also affected.
Lateralisation
-Some physical and psychological functions are controlled by a particular hemisphere. -Generally, the left side of the body is controlled by the right hemisphere, the right side of the body by the left hemisphere.
Cerebral Cortex
-The cerebral cortex covers the inner parts of the brain. It is about 3mm thick and is what separates us from lower animals as it is highly developed.
-The cortex appears grey due to the location of cell bodies- hence the phrase ‘grey matter’.
Four Lobes
Cerebral cortex of both hemispheres is divided into four lobes (frontal, parietal, occipital, and temporal.)
Motor Area
At the back of the frontal lobe (both hemispheres). Controls voluntary movement. Damage may result in loss of control over fine motor movements.
Somatosensory Area
At the back of the parietal lobe. Process sensory information from the skin (touch, heat, pressure etc). The amount of somatosensory area devoted to a particular body part denotes its sensitivity.
Visual Area
In the occipital love at the back of the brain. Each eye sends information from the right visual field to the left visual cortex, and from the left visual field to the right visual cortex.
Auditory Area
In the temporal lobe. Analyses speech based information. Damage may produce partial hearing loss- the more extensive the damage, the more serious the loss.
Language Centres - Broca’s Area
-Speech production
-Identified by Broca in the 1880’s, in the left frontal lobe.
-Damage to this area causes Broca’s aphasia which is characterised by speech that is slow, laborious, and lacking in fluency. Broca’s patients may have difficulty finding words and naming certain objects, also have difficulty with prepositions and conjunctions (e.g. ‘a’, ‘the’, ‘and’).
Language Centres - Wernicke’s Area
-Language understanding
-Identified by Wernicke in the 1880’s, in the left temporal lobe.
-People with Wernicke’s aphasia produce language but have problems understanding it, so they procure fluent but meaningless speech.
-They will often produce nonsense words (neologisms) as part of the content of their speech.
A03 (Support From Neurosurgery)
E- Neurosurgery is used to treat mental disorders. Dougherty et al. studied 44 people with OCD who had a cingulotomy. At follow-up, 30% met the criteria for successful response and 14% for partial response.
E- The success of such procedures strongly suggests that behaviours associated with serious mental disorders may be localised.
A03 (Support From Brain Scan Evidence)
E- Peterson et al. used brain scans to show activity in Wernicke’s area during a listening task and in Broca’s area during a reading task. Also, a study of long-term memory by Tulving et al. revealed semantic and episodic memories are located in different parts of the prefrontal cortex.
E- There now exists a number of sophisticated and objective methods for measuring activity in the brain, providing sound scientific evidence of localisation of function.
A03 (Counterpoint)
Lashley removed areas of the cortex (up to 50%) in rats learning the route through a maze. Learning required 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.
A03 (Language Localisation Model Has Been Questioned)
E- Dick and Tremblay found that very few researchers still believe language is only in Broca’s and Wernicke’s area. Advanced techniques have identified regions in the right hemisphere and the thalamus.
E- 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.
A03 (Case Study Evidence)
E- 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 single individual and conclusions may depend on the subjective interpretation of the researcher.
E- This suggests that some evidence supporting localisation may lack validly, oversimplifying brain processes, and undermining the theory.
