Localisation of Function Flashcards
Localisation of function:
This refers to the principle that specific functions (language, memory, hearing ect.) have specific locations within the brain.
Some functions are more localised than others, e.g vision is more localised than language
What are the four localised functions we need to know:
- Motor cortex
- Somatosensory cortex
- Visual centres
- Auditory centres
Motor Cortex
- Responsible for generation of voluntary motor movements
- Located in frontal lobe, along a bumpy region known as the precentral gyrus.
- Both hemispheres control muscles on the opposite sides of the body (contra-lateral functioning).
- Different areas of the motor cortex are responsible for the movement of different parts of the body.
- They are arranged logically next to one another, e.g. region controlling movement in the foot is next to the region controlling movement in the leg - homonculous layout
Somatosensory Cortex
- Detects sensory events arising from different regions in the body.
- Located in the parietal lobe in the post-central gyrus.
- Processes sensory information related to touch. It uses sensory information from the skin to produce sensations of touch, pressure, pain and temperature which it then localises to specific body regions.
- Both hemispheres have a somato-sensory cortex which processes information from opposite sides of the body - contra-lateral functioning.
Visual Centres
- Located in the visual cortex in the occipital lobe of the brain.
- However, visual processing actually begins in the retina, at the back of the eye, where light enters and strikes the photoreceptors (rods and cones).
- Nerve impulses from the retina are then transmitted to the visual area of the brain via the optic nerve.
- The visual centre spans across both hemispheres.
- The visual centre in the right hemisphere recieves input from the left visual field. - Left hemisphere - input from right visual field.
- The visual cortex contains several different areas, with each of these processing different types of visual information such as colour, shape, movement.
Auditory Centres
- Concerned with hearing.
- Based in auditory cortex - most of this area lies within the temporal lobes on both sides of the brain.
- The auditory pathways begin in the cochlea in the inner ear, where sound waves are converted to nerve impulses, which travel via the auditory nerve to the auditory cortex,
- This is the only cortex that works bilaterally, e.g. sound from right ear processed in right auditory cortex.
What is it called when both hemispheres control muscles on the opposite sides of the body?
Contra-lateral functioning
What are the two language centres:
- Broca’s area
- Wernicke’s area
Broca’s area
- ‘Language centre’ in the posterior portion of the frontal lobe of the left hemisphere.
- This area is believed to be critical for speech production.
- If damaged, effects like slurred speech or speak in broken sentences = Expressive aphasia (Broca’s aphasia)
Wernicke’s area
Located in the posterior portion of the left temporal lobe.
Responsible for speech perception.
Whereas Broca’s patients could understand language but struggled to speak, patients with a lesion in the Wernicke’s area could speak well but were unable to understand language (receptive aphasia)
What connects Broca’s area and Wernicke’s area?
Neural loop
Neural Loop
- Language involves seperate motor and sensory regions located in different corticol regions.
- Neural loop running between Broca’s area and Wernicke’s area connecting them both. On one side Broca, on other end Wernicke.
- Strong connection between Broca and Wernicke’s area allows both areas to communicate which ensures fluent production of language in response to the comprehension.
A strength of localisation of function is that there is supporting evidence for localisation of language centres from research into aphasia studies.
E.g damage to Broca’s region - difficulty in speech production (expressive aphasia) and damage to Wernicke’s area - difficulty with language understanding (receptive aphasia). This confirms our understanding of localisation- specific brain regions have specific functions + damage to those areas might deprive us of these functions - increases validity of LOF as a model of brain function
A strength of localisation of function as a model of functioning is that it is supported by brain scan studies.
Peterson et al used brain scans to demonstrate Wernicke’s area was active during a listening task and Broca’s area was active while reading out loud. As different areas have been active while the brain undertakes different set of functions - demonstrates that functionality is compartmentalized to specific brain regions. Moreover, since it is brain scan research - provides objective and empirical evidence in support of localisation. Increase in validity
Weakness of localisation of function as a model of functioning: oversimplistic
Research suggests that HOW brain areas communicate with each other is more important than WHICH regions control a specific function. Wernicke claimed that although different areas of the brain specialised in different functions, they are interdependant in the sense that in order to execute a function they must interact with eahc other. E.g. in speech production, you need Broca’s area alongside the motor area to move the tongue and the mouth. WB: this suggests that complex behaviours like language occur gradually as info is recieved by one part of the brain and then communicated to other parts. These areas work tg to execute the function. In order to truly understand function, we must consider how parts of the brain communicate with each other. Since localisation does not do this - decrease in validity
