Localisation of Function

Question 1

What is Localisation of function?

Answer 1

Localisation of function is the idea that certain functions (language, memory etc) have certain locations or areas within the brain.

Question 2

What is hemispheric lateralisation?

Answer 2

Some of our functions are controlled or dominated by one hemisphere

Question 3

What is the cerebral cortex?

Answer 3

The outer layer of both hemispheres is the cerebral cortex ‘grey matter’ (like a tea cosy covering the inner parts of the brain).

Question 4

What is the corpus callosum?

Answer 4

There is a bridge in between the two hemispheres called the ‘corpus callosum’. It is essentially a bundle of fibres so that the 2 hemispheres can communicate.

Question 5

What are the four lobes found in the brain?

Answer 5

Fontal lobe: motor area/cortex

Parietal lobe: somatosensory area/cortex

Occipital lobe: visual area/cortex

Temporal lobe: auditory area/cortex

Question 6

Characteristics of Motor area (frontal lobes)

Answer 6

Responsible for voluntary movements by sending signals to the muscles in the body

e.g. arranged in a logical way - the part of the motor area that control finger movements is located near the area that controls the hand.

First discovered by Hitzig & Fritsch (1870) in dogs.

Question 7

Characteristics of Somatosensory area (parietal lobes)

Answer 7

Receives incoming sensory information from the skin to produce sensations related to pain, pressure, temperature etc.

Different parts of the somatosensory area
receive messages from different locations in the body.

Robertson (1995) found that this area of the brain was highly adaptable; braille readers have larger areas in the somatosensory area for their fingertips compared to those who do not have visual impairments.

Question 8

What are the characteristics of the Visual area (occipital lobes)

Answer 8

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

So damage to the LEFT hemisphere can produce blindness in the RIGHT visual field of both eyes for example.

Different parts process different things such as colour/shape/movement

Question 9

What are the characteristics of the Auditory area (temporal lobes)

Answer 9

Analyses and processes acoustic information.

The auditory area contains different parts

The primary auditory area is involved in processing simple features of sound such as pitch, loudness, and tempo (beat).

Question 10

What are the characteristics of Broca’s Area (restricted to left hemisphere)

Answer 10

Paul Broca identified a small area of the left frontal lobe responsible for speech production. He did this whilst treating a patient who could understand spoken language but was unable to produce any coherent words.

After the patients death, Broca conducted a post-mortem examination on the brain and discovered he had a lesion in the left frontal lobe.

Damage to this area of the brain causes ‘Broca’s aphasia’:

Slow, in-fluent speech.

Issues with prepositions and conjunctions (connecting sentences ‘and/but/then’).

Question 11

What are the characteristics of Wernicke’s Area (restricted to left hemisphere)

Answer 11

Carl Wernicke identified a region in the left temporal lobe as being responsible for language comprehension.

Damage to this area of the brain causes ‘Wernicke’s aphasia’:

Difficulties understanding speech

Speech is fluent but meaningless

Anomia – not being able to find the word they need.

However, researchers have found that some patients who have displayed Wernicke’s aphasia without any damage to the left temporal lobe.

This suggests that language comprehension is more complex than originally thought. Further
evidence suggests some left-handed people process language in their right hemisphere.

Question 12

Limitation of localization of function with regards to individual differences.

Answer 12

P: Some psychologists argue that the idea of localization has individual differences.

E: Heratsy (1997) found that women have proportionality larger Broca’s and Wernicke’s areas than men, which can explain the greater use of language amongst women.

I&D: This suggests a level of beta bias in the theory: the differences between males and females have been ignored and the variations in the patterns of language have not been considered.

C: Therefore, we are unable to generalise research examining localisation of function in the brain to males and females equally, as the different brain structures suggest that different considerations are required when
considering the different sexes.

Question 13

Limitation of localization of function with regards to biological reductionism.

Answer 13

P: The claim that functions of the brain are localised has been criticised.

E: Lashley proposed equipotentiality theory which suggests that basic motor and sensory functions are localised but that higher order functions are not. He claimed that intact areas of the brain can take over responsibility for specific brain functions after brain injury.

I&D: Lashley is essentially arguing that the theory of localisation is biologically reductionist as it tries to reduce very complex human behaviour and cognitive processes to one specific brain region. A more thorough understanding of the brain is required to truly understand the complex nature of processes like language.

C: This therefore casts doubt on theories about the localisation of functions if other brain regions can take over their functions.

Question 14

Strength of localization of function: Research Support

Answer 14

P: There are a wealth of case studies on patients with damage to Broca’s and
Wernicke’s areas that have demonstrated their localised functions.

E: For example, Broca’s aphasia is an impaired ability to produce language, in most cases, this is caused by brain damage to Broca’s area.

I&D: Using case studies is an idiographic approach to research and therefore the results of these case studies are difficult to generalise to wider populations as these cases are very unique.

C: Nevertheless, case studies do provide evidence to support the idea that certain elements of language production and comprehension are localised to Broca’s and Wernicke’s regions in the brain.