Localisation of the brain

Question 1

what is localisation??

Answer 1

the theory that specific areas of the brain are associated with particular physical and psychological functions

Question 2

what is the brain divided into.

Answer 2

left hemisphere and right hemisphere

Each hemisphere (side of the brain) is arguably responsible for specific functions.

Question 3

what is hemispheric lateralisation??

Answer 3

Hemispheric Lateralisation: The dominance of one hemisphere of the brain for particular physical and psychological functions

Question 4

what are the different lobes of the brain??

Answer 4

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

Question 5

what does it mean if the area of the brain is contralateral??

Answer 5

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.

Question 6

what does it mean if the area of the brain is somatotopically organised??

Answer 6

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.

Question 7

what are the localised areas of the brain??

Answer 7

motor cortex
somatosensory cortex
visual cortex
auditory cortex

Question 8

where is the motor cortex??

Answer 8

Where is it?
Both hemispheres of the brain have a motor cortex.
It is located in the frontal lobe.

Question 9

what does the motor cortex do??

Answer 9

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.

Question 10

how is the motor cortex organised??

Answer 10

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.

Question 11

where is the somatosensory cortex?

Answer 11

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.

Question 12

what does the somatosensory cortex do?

Answer 12

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.

Question 13

how is the somatosensory cortex organised??

Answer 13

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.

Question 14

where is the visual cortex??

Answer 14

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.

Question 15

what does the visual cortex do??

Answer 15

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.

Question 16

how is the visual cortex organised??

Answer 16

The visual cortex contains several different areas, with each of these areas processing different types of visual information, such as colour, shape or movement.

Question 17

what happens if the visual cortex is damaged??

Answer 17

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.

Question 18

where is the auditory cortex??

Answer 18

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

Question 19

what does the auditory cortex do??

Answer 19

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.

Question 20

what is the auditory cortex do??

Answer 20

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).

Question 21

what are the strengths of localisation??

Answer 21

• supporting research x2

Question 22

what are the weaknesses of localisation??

Answer 22

• contradictory evidence
• research into plasicity
• over-generalised conclusions

Question 23

what is the strength of supporting research #1

Answer 23

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.

Question 24

what the supporting research #2

Answer 24

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.

Question 25

what is the contradictory eveidence for localisation?/

Answer 25

However, a challenge to localisation theory comes from the work of Lashley (1950) contradicting these findings.
E: Lashley removed areas of the cortex (between 10%-50%) in rats that were learning the route through a maze. No area was proven to be more important than any other area in term of the rats’ ability to learn the route.
E: The process of learning seemed to require every part of the cortex rather than being confined to a particular area.
L: This suggests that higher cognitive processes, such as learning, are not localised, but distributed in a more holistic way in the brain.

Question 26

what is the research for plasticity??

Answer 26

The Plasticity of brain function argues that localisation of function is largely incorrect.
E: More recent research into the plasticity of the brain shows that key areas for key functions can be changed in the light of injury / functional recovery after brain injury.
E: It may be the case that simpler functions are likely to be more localised in the brain, eg motor control but more sophisticated aspects of the brain can swap and change if necessary.
L: This could mean suggestions that the brain is highly localised is overstated by research.

Question 27

what is the limitation of over generalised conclusions for localisation??

Answer 27

P: Research evidence has found that lateralisation patterns shift with age.
E: Some research has found clear differences between young children’s and adult brains with regards to lateralised abilities.
E: Szaflarski et al (2006), found most tasks generally become less lateralised in healthy adulthood eg they become less specific.
L: This suggests that conclusions on localised and lateralised functioning need to take into account the role of age and experience, because humans’ ability changes with experience, and some brain functions decay with age.