Localisation of function Flashcards
Definition of localisation
The theory that specific areas of the brain are associated with particular physical and psychological functions
Brain diagram
https://neuroscienceeducation.files.wordpress.com/2015/03/brain-2.png
Motor and somatosensory areas
Both hemispheres of the brain have a motor cortex and a somatosensory cortex, with the left side of the brain responsible for information from the right side of the body, and vice-versa
Motor and somatosensory areas
- the motor cortex
This is responsible for generating and controlling voluntary motor movements
It is located in the rear portion of the frontal lobe, next to the parietal lobe
Different parts of the motor cortex control different parts of the body
Motor and somatosensory areas
- the somatosensory cortex
This responds to sensory information from different parts of the body
It is found in the parietal lobe, next to the motor cortex
This part of the brain detects sensory events such as heat, cold, or pain, and is able to localise these feelings to different body regions
Visual and auditory centres
Visual information travels from the retina in the eye via the optic nerve to the thalamus, which then relays the information to the visual cortex
Visual and auditory centres
- the visual cortex
This is the primary visual centre in the brain
It is responsible for processing visual information, and has different areas for processing different types of information, such as colour, shape and movement areas
It can be found in the occipital lobe of the brain
Auditory information is relayed from the cochlea in the ear, via the brain stem and the thalamus, before arriving in the auditory cortex. Each part of the brain is responsible for decoding some of the information. For example, the brain stem works out the duration and intensity of the sound
Visual and auditory centres
- the auditory cortex
This has the responsibility of recognising and responding to sounds
It is found in the temporal lobes on both sides of the brain
Language centres
- Broca’s area
This is an area of the left frontal hemisphere concerned with the production of speech
Broca, the neurosurgeon, found that patients with a lesion in this area had similar difficulties with language
He found patients including “Tan”, who could understand language but was unable to produce his own speech, other than saying the word ‘tan’
More recently, researchers have found that Broca’s area is also responsible for some cognitive tasks (such as solving math problems)
Language centres
- Wernicke’s area
Wernicke discovered that patients with brain injuries in the posterior portion of the left temporal lobe had difficulties understanding language, even though they could speak
Given that this was the opposite issue to those with lesions in Broca’s area, Wernicke proposed that language required a sensory region (to help with understanding) and a motor region (to allow speech production)
Wernicke’s area is found near the parts of the brain responsible for auditory and visual input. Therefore, sensory input from these regions is transferred to Wernicke’s area where it is decoded
AO3 - research evidence
Harasty et al
Studied 10 men and 11 women post-mortem
Found that women have proportionally larger Broca’s (20.4% larger) and Wernicke’s areas than men, which correlates with superior language skills demonstrated by women
Suggests that there are individual difference in the anatomy of male and female brains
Also suggests language is localised - only 1 area
AO3 - research evidence
Dronkers et al
Conducted post-mortems on the brains of two of Broca’s patients using MRI imaging
Concluded that other area were also lesioned in these patients and so it was not just Broca’s area that was implicated in speech production. While lesions to Broca’s area alone can cause temporary speech disruption, it is usually not a long term issue
However, the damage in Broca’s subjects extended to the superior longitudinal fasciculus, suggesting that this may have caused the persistent nature of the patient’s problems
This suggests that language is not localised to one area of the brain
AO3 - Lashley
His work suggests that the basic motor and sensory functions were localised but that higher mental functions (e.g. consciousness) were not
Lashley claimed that intact areas of the cortex could take over responsibility for specific functions following injury to the area normally responsible for that function
According to this point of view, the effects of damage to the brain would be determined by the extent rather than the location of the damage
This view received some support from the discovery that humans were able to regain some of their cognitive abilities following damage to specific areas of the brain
