Localisation of the brain Flashcards
what is localisation??
the theory that specific areas of the brain are associated with particular physical and psychological functions
what is the brain divided into.
left hemisphere and right hemisphere
Each hemisphere (side of the brain) is arguably responsible for specific functions.
what is hemispheric lateralisation??
Hemispheric Lateralisation: The dominance of one hemisphere of the brain for particular physical and psychological functions
what are the different lobes of the brain??
frontal lobe - Awareness of what we’re doing within our environment (consciousness) and motor movement
temporal lobe - auditory ability
Parietal lobe - sensory perception
Occipital lobe - vision
what does it mean if the area of the brain is contralateral??
situated on or affecting the opposite side of the body. For example, motor paralysis occurs on the side of the body contralateral to the side on which a brain lesion is found. So if you damage the motor cortex in the left hemisphere, the right side of your body will be affected.
what does it mean if the area of the brain is somatotopically organised??
is the point-for-point correspondence of an area of the body to a specific point on the central nervous system. Areas which are finely controlled (e.g. the hands) have larger portions of the cortex whereas coarsely controlled areas (e.g., the trunk) have smaller portions.
what are the localised areas of the brain??
motor cortex
somatosensory cortex
visual cortex
auditory cortex
where is the motor cortex??
Where is it?
Both hemispheres of the brain have a motor cortex.
It is located in the frontal lobe.
what does the motor cortex do??
What does it do?
The primary motor cortex is responsible for the generation of voluntary motor movements.
The process of motor movements is contralateral.
This means that the primary motor cortex on the right frontal lobe controls movement on the left side of the body and vice versa.
This means that any damage to one side of the brain in this area (e.g. through a
stroke) will affect the control of movement on the opposite side of the body.
how is the motor cortex organised??
Somatotopically
This is the point-for-point correspondence of an area of the body to a specific point on the central nervous system.
Areas which are finely controlled (e.g. the hands)
have larger portions of the cortex whereas
coarsely controlled areas (e.g., the trunk) have
smaller portions.
where is the somatosensory cortex?
Both hemispheres of the brain have a somatosensory cortex, with the cortex on one side of the brain receiving sensory information from the opposite side of the body. This means that, like the primary motor cortex, it is contralateral.
It is located in the parietal lobe.
what does the somatosensory cortex do?
The primary somatosensory cortex detects sensory events arising from receptors in the different areas of the body.
Using sensory information from the skin, the somatosensory cortex produces sensations of touch, pressure, pain and temperature, which it then localises to specific body regions.
how is the somatosensory cortex organised??
Somatotopically
This is the point-for-point correspondence of an area of the body to a specific point on the central nervous system.
Areas which have more sensory receptors (e.g.
the hands) have larger portions of the cortex
whereas areas with less sensory receptors
(e.g., the legs) have smaller portions.
where is the visual cortex??
The primary visual centre in the brain is located in the visual cortex.
This is in both hemispheres within the occipital lobe of the brain.
what does the visual cortex do??
Visual processing 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 brain via the optic nerve.
The right hemisphere receives its input from the left-hand side of the visual field and vice versa.
how is the visual cortex organised??
The visual cortex contains several different areas, with each of these areas processing different types of visual information, such as colour, shape or movement.
what happens if the visual cortex is damaged??
Damage to the visual cortex can cause loss of vision (called cortical blindness).
However, visual perception also requires additional input from neighbouring cortical areas (secondary visual areas) and damage to these areas can lead to loss of specific areas of visual perception.
E.g. prosopagnosia – loss of the ability to recognise familiar faces or identify faces at all.
Hurovitz et al. (1999) found that damage to Area VI (a specific area within the visual cortex) leads to a complete loss of ALL vision including visual imagery in dreams.
where is the auditory cortex??
Most of this area lies in the auditory cortex within the temporal lobes in both hemispheres of the brain.
Like the other areas, the auditory process is contralateral with information from the right ear travelling primarily to the left auditory cortex and vice versa
what does the auditory cortex do??
The auditory centre in the brain is concerned with hearing.
The auditory pathways begin in the cochlea in the inner ear, where sound waves are converted to nerve impulses. These travel to the brain stem where a basic decoding takes place (e.g. the duration and intensity of a sound) before moving on to the thalamus and the finally the auditory cortex where the sound is recognised and interpreted.
what is the auditory cortex do??
Damage to the auditory cortex produces difficulties in processing and understanding sounds rather than total deafness (e.g. there may be an inability to perceive a certain pitch).
what are the strengths of localisation??
- supporting research x2
what are the weaknesses of localisation??
- contradictory evidence
- research into plasicity
- over-generalised conclusions
what is the strength of supporting research #1
There is research support from human clinical case studies of the loss of specific abilities after restricted brain damage.
E: For example, receptive aphasia following damage to Wernicke’s area and amnesia following damage to specific areas of the hippocampus.
E: HM damaged his hippocampus during surgery for epilepsy and created irreversible damage to memory.
L: This suggests that localisation of functioning is supported by real life evidence.
what the supporting research #2
There is also supporting evidence for localisation of function from brain scans.
E: For instance, Buckner
and Peterson (1996) used brain scans to reveal that semantic and episodic long term memories reside in different parts of the prefrontal cortex. Similarly, research by Maguire et al. (2000) suggests navigational skills reside in the posterior hippocampal regions.
E: These studies confirm localised areas for everyday behaviours.
L: Therefore, these objective methods for measuring brain activity have provided sound scientific evidence that many brain functions are localised to specific areas.
