Localisation of Function in the Brain

Question 1

What is localisation?

Answer 1

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

Question 2

What is the frontal lobe responsible for?

Answer 2

The motor cortex, responsible for awareness of what we are doing in our environment

Question 3

What is the parietal lobe responsible for?

Answer 3

The somatosensory cortex, sensory and motor movements

Question 4

What is the temporal lobe responsible for?

Answer 4

The auditory cortex

Question 5

What is the occipital lobe responsible for?

Answer 5

The visual cortex

Question 6

What is hemispheric lateralisation?

Answer 6

the dominance of one hemisphere of the brain for physical and psychological functions. The two halves of the brain are functionally different.

Question 7

What is the motor cortex?

Answer 7

• The primary motor cortex is responsible for the generation of voluntary motor movements and is in the frontal lobe
• Both hemispheres of the brain have a motor cortex
• The process of motor movements is contralateral
• Somatopically organised

Question 8

What does contralateral mean?

Answer 8

the primary motor cortex on the right frontal lobe controls movement on the left side of the body and the primary motor cortex on the left frontal lobe controls movement on the right side of the body

Question 9

What is the somatosensory cortex?

Answer 9

• The primary somatosensory cortex detects sensory events arising from receptors in the different areas of the body and is in the parietal lobe
• Using sensory information the somatosensory cortex produces sensations of touch, pressure, pain and temperature which is then localized to specific body regions
• Both hemispheres have a somatosensory cortex and control opposite sides of the body, it is contralateral
• It is also somatotopically organized

Question 10

What is the visual cortex?

Answer 10

• The primary visual center in the brain is in the visual cortex and is in the occipital lobe
• Visual processing begins in the retina at the back of the eye where light enters and strikes photoreceptors
• Nerve impulses from the retina are then transmitted to the brain via the optic nerve
• The visual cortex spans both hemispheres and it is largely contralateral
• The visual cortex contains several different areas with each one processing different types of visual information e.g., color, shape or movement
• Damage to the visual cortex can cause loss of vision known as corticol blindness
• Visual perception also requires additional input from secondary visual areas and damage to these can lead to loss of specific areas of visual perception e.g., prosopagnosia – loss of ability to recognize familiar faces or identify faces at all

Question 11

What is the auditory cortex?

Answer 11

• Concerned with hearing, lies within the temporal lobe in both hemispheres of the brain
• Auditory process is contralateral
• Auditory pathways begin in the cochlea in the inner ear where sound waves are connected to nerve impulses that travel to the brain stem where basic decoding takes place
• Moves to the thalamus and then the auditory cortex where sound is recognized and interpreted
• Damage to the auditory cortex produces difficulties in processing and understanding sounds rather than total deafness

Question 12

Positive evaluation of localisation of brain function - research to support

Answer 12

There is research to suggest vision is localized. For example, 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. This does therefore support the idea that the visual cortex has localized function for vision because when this was damaged this function was completely lost. Therefore, this research adds validity to the claim

Question 13

Positive evaluation of localisation of brain function - case studies to support

Answer 13

There is a wealth of case studies on patients with damage to Broca’s area (such as a case study of Patient Tan who could only say the word ‘tan’ as the area for language production was damaged) and case studies on the Wernicke’s area that have demonstrated their different functions in language. For example, Broca’s aphasia is an impaired ability to produce language, in most cases this is caused by brain damage to the Broca’s area. Wernicke’s aphasia is an impairment of language perception, demonstrating the important role played by the brain region in comprehension of language. This demonstrates that certain areas of language production and comprehension are indeed localized in these areas

Question 14

Negative evaluation of localisation of brain function - research that doesn’t support

Answer 14

However, other research questions the idea of localization of brain function. Lashley made lesions in different areas of the brains of rats who were put into a maze, found large lesions on visual areas impaired maze learning, but smaller lesions covering the same brain areas had no effect. Concluded that functions such as learning were spread widely across brain areas and were not localized to specific regions. He called this ‘Law of mass action’ and this reduces validity of the theory.
COUNTERARGUMENT: Rats, biological continuity???

Question 15

Negative evaluation of localisation of brain function - need to look in a more holistic manner

Answer 15

Other factors presented by Lashley also questioned the concept of localization as he proposed the idea of equipotentiality. When the brain is damaged and a particular function affected, the rest of the brain seems to recognize itself to recover the lost function. It shows plasticity, this is where surviving brain circuits ‘chip in’ so the same neural action can be achieved. This has been shown in certain documented cases of stroke victims who have recovered their abilities originally lost. This means that it may be better to look at the brain in a more holistic way rather than in parts to fully understand functionality