Lesson 6: Localisation Of Function

Question 1

What is the localisation of function

Answer 1

Localisation of function refers to the principle that functions (e.g. vision, hearing, memory, etc.) have specific locations within the brain. Research has shown that some functions are more localised than others. The motor and somatosensory functions are highly localised to particular areas of the cortex. Other functions are more widely distributed. The language system uses several parts of the brain, although some components, such as speech production, may be localised (Broca’s Area).

Question 2

How many hemispheres does the cerebrum have

Answer 2

2 - left hemisphere and right hemisphere

Question 3

How many lobes are there in the cerebrum

Answer 3

4 - frontal lobe, parietal lobe, occipital lobe and temporal lobe

Question 4

What do visual centres do

Answer 4

The visual cortex processes information such as colour and shape. It is in the occipital lobe of BOTH hemispheres of the brain. Visual processing starts in the retina where light enters and strikes the photoreceptors. Nerve impulses from the retina are transmitted to the brain via the optic nerve. The majority terminate in the thalamus, which acts as a relay station, passing the information onto the visual cortex.

Question 5

What do auditory centres do

Answer 5

The auditory cortex processes information such as pitch and volume. It lies within the temporal lobe in BOTH hemispheres of the brain. The auditory pathway begins in the cochlea in the inner ear, where sound waves are converted to nerve impulses, which travel via the auditory nerve to the auditory cortex. Basic decoding occurs in the brain stem, the thalamus carries out further processing before impulses reach the auditory cortex.

Question 6

What does the motor cortex do

Answer 6

The motor cortex is responsible for voluntary movements. It is located in the frontal lobe of BOTH brain hemispheres. Different parts of the motor cortex control different parts of the body. These areas are arranged logically next to one another. Damage to this area can cause a loss of muscle function/paralysis in one or both sides of the body (depending on which hemisphere/hemispheres have been affected).

Question 7

What does the Somatosensory Cortex do

Answer 7

The somatosensory cortex is responsible for processing sensations such as pain and pressure .It is located in the parietal lobe of BOTH hemispheres

Question 8

What are the two language centres

Answer 8

Broca’s area and Wernicke’s Area

Question 9

Broca’s Area

Answer 9

This area is named after Paul Broca who treated patients who had difficulty producing speech. He found that they had lesions to the LEFT hemisphere of the frontal lobe. Damage to the Broa’s Area causes Expressive Aphasia. This disorder affects language production but NOT understanding. Speech lacks fluency and patients have difficulty with certain words which help sentences function (e.g. ‘it’ and ‘the’).

Question 10

Wernicke’s Area

Answer 10

This area is in the LEFT hemisphere of the temporal lobe. Carl Wernicke found that patients with a lesion to this area could speak but were unable to understand language. Wernicke concluded that this area is responsible for the processing of spoken language. The Wernicke Area is connected to the Broca’s Area by a neural loop. Damage to the Wernicke’s Area causes Receptive Aphasia. This disorder leads to an impaired ability to understand language.

Question 11

Language is only in the …

Answer 11

Left hemisphere

Question 12

Disadvantages of Localisation of Function

Answer 12

• Some functions are more localised than others. Motor and somatosensory functions are highly localised to specific areas of the cortex. However, higher functions (e.g. personality and consciousness) are much more widely distributed. Functions such as language are too complex to be assigned to just one area and instead involve networks of brain regions.
• Equipoteniality theory (Lashley, 1930) holds that higher mental functions are not localised. The theory also claims that intact areas of the cortex take over responsibility for a specific cognitive function following injury to the area normally responsible.
• Dronkers et al. (2007) re-examined the preserved brains of two of Broca’s patients. MRI scans revealed that several areas of the brain had been damaged. Lesions to the Broca’s Area cause temporary speech disruption they do not usually result in severe disruption of language. Language is a more widely distributed (and less localised) skill than originally thought.
• It may be that how brain areas communicate with each other is more important than specific brain regions. Dejerine (1892) reported a patient who could not read because of damage between the visual cortex and Wernicke’s area.
• Bavelier et al. (1997) found that there are individual differences in which brain areas are responsible for certain functions. They found that different brain areas are activated when a person is engaged in silent reading. They observed activity in the right temporal lobe, left frontal lobe and occipital lobe. This means that the function of silent reading does not have a specific location within the brain