Localisation of Function

Question 1

Localisation of function

Answer 1

The theory that different areas of the brain are responsible for different behaviours, processes, or activities.

Question 2

During the 19th century, scientists discovered that…

Answer 2

specific areas of the brain are associated with particular physical and physiological functions.

Question 3

The holistic theory of the brain

Answer 3

All parts of the brain were involved in the processing of thought and action.

Question 4

What did Broca and Wernicke argue regarding localisation?

Answer 4

Different parts of the brain perform different tasks and are involved with different parts of the body. It follows then, that if a certain area of the brain becomes damaged through illness or injury, the function associated with that area will also be affected.

Question 5

The brain is divided into…

Answer 5

2 symmetrical hemispheres.

Question 6

Lateralisation

Answer 6

Some of our physical and psychological functions are controlled or dominated by a particular hemisphere.

Question 7

Right versus left.

Answer 7

Activity on the left-hand side of the body is controlled by the right hemisphere and activity on the right-hand side of the body is controlled by the left hemisphere.

Question 8

Cerebral cortex

Answer 8

Outer layer of both hemispheres covering the inner parts of the brain.
About 3mm thick.
This is what separates us from other animals because the human cortex is much more developed.

Question 9

Why does the cortex appear grey?

Answer 9

Due to the location of cell bodies.

Question 10

The cortex of both hemispheres is subdivided into…

Answer 10

4 Lobes.

Question 11

4 lobes

Answer 11

Frontal Lobe.
Parietal Lobe.
Temporal Lobe.
Occipital Lobe.

Question 12

Each lobe is associated with…

Answer 12

different functions.

Question 13

Motor area

Answer 13

Back of both frontal lobes.
Controls voluntary movement on the opposite side of the body.
Damage to the area results in loss of control over fine movements.

Question 14

Somatosensory area

Answer 14

Front of both parietal lobes.
Separates from the motor area by a valley - central sulcus.
Where sensory information from the skin is represented.
The amount of somatosensory area devoted to a particular body part denotes its sensitivity.

Question 15

Visual area

Answer 15

Occipital lobe.
Each eye sends information from the right visual field to the left visual cortex and from the left visual field to the right visual cortex.
Damage to the left hemisphere can produce blindness in the right visual field of both eyes.

Question 16

Auditory area

Answer 16

Temporal lobes.
Analyses speech-based information.
Damage may produce partial hearing loss; the more extensive the damage, the more extensive the loss.

Question 17

Which hemisphere are the language centres housed in?

Answer 17

Left.

Question 18

Broca’s area

Answer 18

Identified by Paul Broca in 1880s.
Left frontal lobe responsible for speech production.
Damage to area = Broca’s aphasia - slow, laborious, and lacking in fluency.

Question 19

Wernicke’s area

Answer 19

1880s - Karl Wernicke.
Left temporal lobe - responsible for language comprehension.
Damage - Wenicke’s aphasia - produce nonsense words as part of content of their speech.

Question 20

Strength - Brain scan evidence of localisation

Answer 20

A wealth of evidence supporting the idea that many neurological functions are localised, especially in relation to language and memory.
Petersen et al (1988) used brain scans to demonstrate how Wernicke’s area was active during a listening task and Broca’s area was active during a reading task, suggesting that these areas of the brain have different functions.
Similarly, a study of LTM by Tulving et al (1994) revealed semantic and episodic memories reside in different parts of prefrontal cortex. Now exists a number of highly sophisticated and objective methods for measuring activity in the brain providing sound scientific evidence of localisation of brain function.

Question 21

Strength and Limitation - Neurosurgical evidence

Answer 21

Practice of surgically removing or destroying brain areas to control aspects of behaviour developed in 1950s. Early attempts were brutal and imprecise and typically involved severing connections in the frontal lobe in an attempt to control aggressive behaviour.
Controversially, neurosurgery is still used today in extreme cases of OCD and depression.
E.g. Dougherty et al (2002) reported on 44 OCD patients who have undergone a cingulotomy.
Post-surgical follow-up at 32 weeks, a third met the criteria for a successful surgery and 14% for partial response.
Success of procedures strongly suggests that symptoms and behaviours associated with serious mental disorders are localised.

Question 22

Strength - Case study evidence

Answer 22

Unique cases of neurological damage support localisation theory such as Phineas Gage.

Question 23

Weakness - Lashley’s research

Answer 23

The work of Karl Lashley (1950) suggests that higher cognitive functions, such as the processes involved in learning, are not localised but distributed in a more holistic way in the brain.
Lashley removed areas of the cortex, between 10 and 50%, in rats that were learning a maze. No area was proven to be more important than any other area in terms of the rats’ ability to learn the maze.
The process of learning appeared to require every part of the cortex, rather than being confined to a particular area.
This seems to suggest that learning is too complex to be localised and requires the movement of the whole of the brain.

Question 24

Weakness - plasticity

Answer 24

A further and compelling argument against localisation of function is the notion of cortical remapping or plasticity. When the brain has become damaged, through illness or accident, and a particular function has been compromised or lost, the rest of the brain appears able to reorganise itself in an attempt to recover the lost function.
Lashley described this as the law of equipotentiality whereby surviving brain circuits ‘chip in’ so the same neurological action can be achieved.
Although this does not happen every time, there are several documented cases of stroke victims being able to recover those abilities that were seemingly lost as a result of the illness.

Question 25

IDA - Biologically Reductionist.

Answer 25

Critics argue that theories of localisation are biologically reductionist in nature and try to reduce very complex behaviours and cognitive processes to one specific brain region. Such critics suggest that a more thorough understanding of the brain is required to truly understand complex cognitive processes like language.

Question 26

IDA - Beta bias.

Answer 26

Some psychologists argue that the idea of localisation fails to take into account individual differences. Herasty (1997) found that women have proportionally larger Broca’s and Wernicke’s areas than men, which can perhaps explain the greater ease of language use amongst women. This, however, suggests a level of beta bias in the theory: the differences between men and women are ignored, and variations in the pattern of activation and the size of areas observed during various language activities are not considered.