Biopsychology - Localisation of function in the brain and hemispheric lateralisation

Question 1

What is localisation of function?

Answer 1

Belief that specific areas of the brain are associated with specific cognitive processes

Question 2

Broca’s Area

Answer 2

Function: Responsible for converting thought into speech

Location: Frontal lobe - left hemisphere

Question 3

Wernicke’s Area

Answer 3

Function: Understanding speech

Location: Temporal lobe - left hemisphere

Question 4

Aphasia

Answer 4

inability (or impaired ability) to understand or produce speech

occurs when there is damage to either the broca’s or wernicke’s area

Question 5

Three concentric layers of the brain

Answer 5

The central core
The limbic system
The cerebrum

Question 6

The central core

Answer 6

Involuntary movements such as breathing/sleeping

Regulates eating and drinking + endocrine system

Homoeostasis: the process by which the body maintains a constant physiological state

Question 7

The limbic system

Answer 7

Controls emotions

Around the central core

Key roles in memory

Question 8

The cerebrum

Answer 8

Regulates higher intellectual processes

Contains neuronal cell bodies that are responsible for muscle control and sensory perception

Made up of right and left hemispheres connected by corpus callosum (bundle of fibres) that enable messages exchange between left and right hemispheres

Question 9

Motor Cortex

Answer 9

Function: Voluntary motor movements

Location: Frontal lobe

Question 10

Somatosensory Cortex

Answer 10

Function: receiving and processing sensory information

Location: Parietal lobe

Question 11

Visual Cortex

Answer 11

Function: Processes visual information such as colour shape or movement

Location: Parietal lobe

Question 12

Auditory Cortex

Answer 12

Function: Concerned with hearing

Location: Temporal lobe

Question 13

Petersen et al

Answer 13

Petersen et al used brain scans to demonstrate how Wernicke’s area was active during a listening task and Broca’s area was active during reading task showing they have different functions

Question 14

Phineas Gage

Answer 14

Phineas Gage - unique case of neurological damage that supports localisation theory
Gage was involved in an accident where a pole went through the left side of his head damaging his frontal lobe and this affected his personality - went from calm/reserved to quick tempered/rude. This change in personality supports the idea that the frontal lobe is responsible for regulating mood
C: difficult to generalise findings

Case study evidence of
localisation

Question 15

Plasticity as a criticism of localisation of function

Answer 15

When the brain gets damaged through illness/accident and a particular function is lost, the rest of the brain is able to reorganise itself to recover the loss of function. This suggests that localisation is not fixed to specific areas and the brain is working as a whole unit rather than specific areas for specific functions.

Question 16

Lashley

Answer 16

Karl Lashley removed (between 10-50% of) area in the cortex of rats placed in a learning maze and found no area was found to be more important than any other in terms of the rats’ ability to learn the maze as learning appeared to require every part of the cortex rather than one area. This suggests learning is too complex to be localised and requires the whole of the brain

Counter evidence of localisation of function

Question 17

Brain plasticity (Cortical remapping)

Answer 17

refers to the brain’s ability to change and adapt as a result of experience …

Question 18

Synaptic pruning

Answer 18

frequently used connections are strengthened and rarely used connections are deleted

Question 19

Research into plasticity

Answer 19

Maguire et al studies the brains of London taxi driver and found significantly more greymatter in the hippocampus than a matched control group

The hippocampus is associated with the development of spatial and navigational skills in humans and other animals

Question 20

Functional recovery of the brain after trauma

Answer 20

Following physical injury (or a stroke), unaffected areas of the brain are able to adapt and compensate for those areas that are damaged

This functional recovery is another example of neural plasticity

Question 21

What happens in the brain during recovery?

Answer 21

The brain is able to rewire and reorganise itself by forming new synaptic connections close to the area of the damage

Involves:

1. Axon sprouting: the growth of new nerve endings which connect with other damaged nerve cells to form new neural pathways
2. Reformation of blood vessels
3. Recruitment of homologous areas on the opposite side of to perform specific task e.g. of the Broca’s area was damaged on the left, the right side equivalent would carry out its function

Question 22

Lieperta et a

Answer 22

the brain can only ‘repair’ itself up to a specific point, after which motor therapy or electrical stimulation is needed

Lieperta et al (1998) found that after constraint-induced movement therapy, the motor performance of stroke patients improved significantly.

This shows although the brain has the ability to ‘fix itself’ to a point, this process requires further intervention to be completely successful

limitation of plasticity

Question 23

Negative plasticity

Answer 23

The brain’s ability to rewire itself can sometimes have maladaptive behavioural consequences. 60-80% of amputees have been known to develop phantom limb syndrome (the continued experience of sensations of the missing limb as it were still there) Ramachandran and Hirsterin found these unpleasant/painful symptoms are due to cortical reorganisation in the somatosensory cortex that occurs as a result of limb loss

Question 24

Hubel and Wiesel’

Answer 24

Hubel and Wiesel’s study involved sewing one eye of a kitten shut and analysing the brain’s cortical responses. It was found that the area of the visual cortex associated with the shut eye was not idle (as predicted) but continued to process information from the open eye however human behaviour is very different from animal behaviour, so may not be generalisable to humans

Support from animal studies for plasticity

Question 25

Kühn et al

Answer 25

Kühn et al recruited 48 people who had not played any computer games for the previous 6 months and randomised them into 2 groups: 23 played Super Mario for at least 30 mins everyday + 25 were just asked not to play any computer games during the study. They found a significant increase in grey matter in various regions of the brain which supports the idea of plasticity and the brain’s ability to adapt as a result of new experience,

Research support for plasticity

Question 26

Criticism of Maguire’s study

Answer 26

A clear cause and effect relationship between changes in the brain cannot be established as taxi drivers were not tested before becoming taxi drivers so a clear change in the structures of the brain as a result of their experiences cannot be concluded

Question 27

Hemispheric lateralisation

Answer 27

idea that the two halves of the brain are functionally different and that each hemisphere has functional specialisations,

For example: specialised areas areas associated with language are found in one of the brain;s left hemisphere rather rather than both

Question 28

What is split-brain research?

Answer 28

A series of studies which began in the 1960s involving epileptic people what had experienced surgical separation of the hemispheres of the brain which allowed researchers to investigate the extent to which brain function is lateralized

Question 29

Reason for using split brain studies to research hemispheric lateralisation

Answer 29

Communication line between the two hemispheres was removed demonstrated the extent hemispheres were specialised for certain functions and whether the hemispheres performed tasks independently

Question 30

Procedure of split brain studies

Answer 30

An image would be projected into the individual’s right visual field (processed by the left hemisphere) and vice versa

Question 31

Findings of split brain studies

Answer 31

When patients were shown a word in their right visual field, they were able to describe what they saw; nevertheless, when they were shown aword in their left visual area, they were unable to describe what they saw.

Conclusion: language functions are exclusively found in the left hemisphere; otherwise, the patient would be able to communicate what they observed in their left visual field (which goes to the right hemisphere)

Question 32

Strength of the Sperry’s research - methodology

Answer 32

The experiments made use of highly specialised and standardised procedures. Sperry asked participants to stare at a given point - (the fixation point) and the image projected would be flashed for one-tenth of a second so the split brain individual would not have time to move their eye across the images and spread the information across both sides of the visual field and subsequently both sides of the brain. This ensured that only one hemisphere was receiving information

Question 33

Issues of generalisation with split brain research

Answer 33

There were only 11 people who took part in all variations of the procedure. All had a history eplipetic seizures so it could be argued that this may have caused unique changes in the brain that may have influenced the findings thus the results are not generalisable to wider population

Question 34

Turk et al

Answer 34

Lateralisation is not fixed…
Turk et al discovered a patient (J.W) who suffered damage to the left hemisphere but developed the capacity to speak in the right hemisphere, eventually leading to the ability to speak about the information presented to either side of the brain. This suggests that language may not be restricted to the left hemisphere and perhaps lateralisation is not fixed and that the brain can adapt following damage to certain areas.