Biopsychology - A2 (Area's of the Brain (Visual Centres:
Biopsychology - A2
Area's of the Brain
Motor and Sensory Areas:
- The Motor Cortex:
- This is responsible for the generation of voluntary movements. It is located in the frontal lobe of the brain.
- Both hemispheres of the brain have motor cortex, with the motor cortex on one side of the brain controlling the muscles on the opposite side of the body.
- Different parts of the motor cortex control different muscles.
- The primary visual centre in the brain is located in the visual cortex, in the occipital lobe of the brain
- The visual cortex spans both hemispheres with the left hemisphere receiving its input from the right hand side of the visual field.
- The visual cortex contains several different areas, with each of these areas processing different types of visual information, such as colour, shape or movement
- The auditory centre is concerned with hearing. The primary auditory cortex in both hemispheres receives information from both ears via two pathways that transmit info about what the sound is and its location.
- The information from the right ear goes to the left hemisphere but some is transmitted to the right primary auditory cortex too.
- If this area is injured, an individual would have difficulty hearing complex sounds
- Meyer's research suggests it processes auditory imagery as well, e.g. the sounds imagined when watching a silent film
- Broca's Area:
- Speech production - people with damaged Broca's areas have difficulty speaking
- The Case Study of Leborgne: Leborgne had epilepsy and lost the ability to speak. Once he had died Broca performed an autopsy and found damage in only one part
- Wernicke's Area:
- Important for understanding language and accessing words
- The Somatosensory Cortex:
- This detects sensory events arising from different regions of the body. It is located in the parietal lobe of the brain.
- It perceives touch, so the amount of neuronal connections needed dictates the amount of somatosensory cortex needed for that area of the body.
- As with the motor cortex, both hemispheres have somatosensory cortex, with the cortex on on side of the brain receiving sensory information from the opposite side if the body
Split Brain Research
- In 'normal' brains it is difficult to study lateralisation of functions as the two hemispheres are connected and communication between the hemisphere is very rapid.
- However, Split-brain patients have had the corpus callosum cut to reduce the effects of epilepsy.
- Sperry & Gazzaniga were the first to study the capabilities of split-brain patients.
Findings from Split Brain Research:
- Unfamiliar tasks where the two hands are required to work together cannot be done- evidence of contralateral control of motor tasks
- At first the two hemispheres act independently but then the left hemisphere takes control and suppresses the right through smaller pathways connecting the two hemispheres - evidence that the left hemisphere is usually dominant.
- The split hemispheres may cooperate with each other through other external means - e.g. the right hemisphere causing a frown when the left causes a spoken wrong answer
- Sperry used the divided field technique with split-brain patients.
- He found that if split-brain patients were flashed a word or object to their right visual field they could correctly say or name the object. However, if they were flashed a word or object to their left visual field they could not say it or name the object.
- This research gives support for hemispheric lateralisation
- Stirling found that the right hemisphere is better at identifying the emotional aspects of language.
- Damage to an area in the right hemisphere equivalent to Broca's area causes words to be spoken without emotion.
- Damage to an area in the right hemisphere equivalent to Wernicke's area causes difficulty in interpreting emotional tone.
- However, Sperry also found that if split brain patients were flashed a word in their left visual field, although they could say it they could correctly pick out the corresponding object by feel with their left hand.
- Split brain research has been useful in understanding the role of each hemisphere and the extent to which they are lateralised
- It is problematic to assume evidence is not flawed.
- Lacks population validity - small number of patients to study
- Surgery may produce other side effects