Localisation And Laterisation Of Fucntion

Question 1

What is the localisation of function?

Answer 1

Localisation of function refers to the principle that function such as language, memory hearing etc have specific locations in the brain.
The brain is thought to made up of two hemispheres the right and left hemispheres, and four lobes the frontal lobe, pariental lobe, occipital lobe, and temporal lobe.

Question 2

Visual and auditory centres

Answer 2

Visual centres- the visual cortex is in the occipital lobe of both hemisphere, visual processing starts at the retina and through the optic nerve the impulses enter the brain and terminate near the thalamus which passes information into the visual cortex.

Auditory centres- the auditory cortex lies within the temporal lobe in both hemispheres, the auditory pathways begin in the Omer which travel to the auditory cortex via the auditory nerve. Basic decoding occurs in the brain stem and the thalamus carries out further processing.

Question 3

Motor and somatosensory areas

Answer 3

The motor cortex is responsible for the generation of voluntary motor movement, it is located in the frontal lobe of both hemispheres. Different parts of the motor cortex control different body parts and are arranged logically next to each other, damage to this area can lead to muscle paralysis on one or both sides of the buddy depending if one or both hemispheres where affected.

The somatosensory cortex- this area detects events arising from different regions of the body, it is located in the parietal lobe of both hemispheres and using sensory data from the skin the cortex produces sensations of touch, pressure, pain and temperature and localises it to a part of the body.

Question 4

Language centres

Answer 4

Broca’s area- this area is named after Paul Broca, it is found in the left hemisphere of the frontal lobe . Damage to it causes expressive aphasia which a language problem which affect language production but not understanding.speech lacks fluency and has trouble with certain words which help sentences function such as it and the.

Wernicke’s area is in the left hemisphere of the temporal lobe, named after Carl Wernicke. It is responsible for processing spoken language and is connected to Broca’s area by a neural loop. Damage to it causes receptive aphrasia, which impares language undertsjshf not production so they can speak fluently but often in gibberish and not understand what you are saying, those affected are often not aware of it.

Question 5

Evaluation of localised function

Answer 5

• ) some functions are more localised then others, motor and somatosensory are highly localised but other functions such as personality is widely distributed
• ) Equipoteniality theory (lashley, 1903) holds that higher mental functions are not localised and intact areas of the cortex take over responsibility for a specific function after injury of the normally responsible area.
• ) Dronkers (2007) re examined the preserved brains of two of Broca’s patients showed that several areas of the brain had been damage, lesions to the Broca’s area cause temporary speech disruption and do not cause a severe disruption of language which is more widely distributed then we thought.
• ) Bavelier (1997) found that there are individual differences in which brain areas are activated when a person is engaged in silent reading with activity in left frontal lobe, right temporal lobe and left occipital lobe.
• ) it may be how brain areas communicate being more important as is reported a patient who couldn’t read because of damage between the visual cortex and Wernickes area.

Question 6

What is lateralisation of function?

Answer 6

Lateralisation of function- this is the idea that two hemispheres of the brain have different specifications. The right hemisphere of the brain is responsible for the left hand side of the body while the left hemisphere is responsible for the right.
Studies show the left is dominant for language while the right is dominant for facial recognition, the two hemispheres are connected by a bundle of nerve fibres called the corpus callosum.

Question 7

Evaluation of lateralisation of function

Answer 7

+) An advantage of brain lateralisation is that it increases neural processing capacity which is adaptive. By using one hemisphere in one task the other can focus on another function. Rogers etc al (2004) found that lateralisation in chickens is associated with an ability to perform two tasks simultaneously.

-) JW developed the capacity to speak using his right hemisphere so he could speak about information presented to the left or right hemisphere suggesting there are individual differences in how the brain functions.

Question 8

Split brain research

Answer 8

Surgeons have cut the corpus callosum in the last to prevent epileptic seizures in people due to violent electrical activity crossing between hemispheres. These people are referred to as split brain patients as the hemispheres of their brain can’t communicate inside the brain.

Sperry and Gazzaniga (1968) investigate split brain patients and found that information in the left visual field goes to the right hemisphere and vice versa. This information cannot travel between one hemisphere and another, the patients where asked to stare at a dot in the centre of a screen information was shown in either the right or left visual fields. They are then asked to make responses with either their left hand (Right hemisphere), right hand ( left hemisphere) or verbally (left hemisphere) without seeing what their hand was doing.

There may have been an image if a dog in the right visual field and they will be able to answer dog verbally since the information went to the left hemisphere, if it is the left visual field they will not be able to say what they have seen and will probably deny they have seen anything. But they can draw a picture of a cat with their left hand as the right hemisphere controls that hand.

Question 9

Split brain research evaluation

Answer 9

• ) the disconnection between hemispheres is greater in some patients more then others and some patients have had drug therapy for epilepsy longer then others. This can effect the way their brain works, this means split brain research can’t be generalised to the general population.
• ) many split brain studies have as few as three participants making generalisation hard.
• ) in the real world a severed corpus callosum can be compensated for by the unrestricted use of both visual fields this means the research lacks ecological validity