Paper 2 - Biopsychology - Circadian Rhythms Flashcards
What process has split brain patients undergone?
commissurotomy
What was the aims of Sperry’s research?
To investigate the hemispheric functioning of split brain patients.
What type of experiment was Sperry’s experiment?
To investigate the hemispheric functioning of split brain patients.
Who were the participants in Sperry’s experiment?
11 individuals had their corpus collosum removed to treat epilepsy
What was the procedure in Sperry’s experiment?
Pps were asked to perform a range of tasks and their performance was compared with pps with no interhemispheric disconnection. The tasks involved presenting information to one hemisphere by sending it to only one visual field. They were blindfolded so that only one eye was receiving the information
In other tasks, their hands were screened from them so they could not see objects placed in front of them i.e. an object shown to the right visual field, or placed in the right hand will only be perceived by the left hemisphere.
What does hemispheric lateralisation mean?
This is when the 2 brain hemispheres are separated by removing part of or all of the Corpus Collosum
What joins the 2 hemispheres?
The Corpus Collosum
What impact was there on the split brain monkey?
No impact on the monkey. They were accepted back as king of the colony straight away. When the monkeys were given a task to push a button to receive to retrieve a treat, when it was presented in thier right visual field they could not push the button. But they could grab food with both hands
When was Sperry’s investigation?
1968
What were the results of Sperry’s investigations?
• Visual material shown to the left hemisphere right visual field) can be described in speech and writing. If it is shown to the right hemisphere (left visual field) participants will deny seeing anything, but they are able to pick out the correct object with their left hand;
• If two different figures are shown to the hemispheres then the participant will be able to draw what they have seen in the left visual field with their left hand (right hemisphere). However, if asked what they have drawn they will tell you the object they saw in the right visual field (left hemisphere).
• An object placed in the right hand (left hemisphere) can be described and named. An object placed in the left hand (right hemisphere) cannot be described or named, but can selected from other objects.
• Objects can only be selected again by the hand in which they were horiginally placed. The left hand will ignore objects that the right hand is looking for, and vice versa. As Sperry commented, it is like two different people are completing the same task.
What were the conclusions of Sperry’s experiments?
There is some lateralisation of function between the hemispheres
What are the strengths of Sperry’s experiments?
• High levels of control
• Clearly demonstrated the lateralisation of function between the left and right hemisphere;
• Although it was a small sample, it was probably representative of the people who have had this operation;
What are the weaknesses of Sperry;s study?
• The tasks are low in ecological validity- the problems participants faced in the task would probably not be a problem in real life;
• It may not be possible to compare the brains of severe epileptics who have undergone brain surgery to the brains of ‘normal’ people;
• There were only 11 participants which is a small sample to generalise from.
What may the case study of Tony and Joe show us?
Plasticity can’t fully repair the brain
What does the case studies of Joe and Tony suggest about quality of life?
It suggests that this surgery can be used to improve quality of life. But they should always try to take out as little as possible to allow some communication. But rehabilitation is sometimes required.
What are the positive evaluations for split brain research?
It demonstrated lateralised brain functions
The methodology is good
What are the negative evaluations of split brain research?
There is theoretical bias
Issues with generalisation
Differences in function may be overstated
Explain the positive evaluation of split brain research: demonstrated lateralised brain functions
The pioneering work into the split brain phenomenon has produced an impressive and sizeable body of research findings - the main conclusion of which appears to be that the left hemisphere is more geared towards analytics and verbal tasks, whilst the right is more adept at performing spacial tasks and music
The right hemisphere can only produce rudimentary words and phrases but contributes emotional and holistic content to language
Generally what do the left and right hemisphere do?
left hemisphere - analyser
right hemisphere - synthesiser
Explain the positive evaluation of split brain research: Good methadology
Experiments use highly specialised and standardised procedures
The method used was ingenious - typically participants would be asked to stare at a given point the “fixation point” whilst one eye is blindfolded
The image projected would appear for 0.1 seconds so the participant doesn’t have time to move their eye across the image and so spread the information across both sides of the visual field and both sides of the brain
Sperry was able to develop a useful and well controlled procedure based of the original research
Explain the negative evaluation of split brain research: Theoretical bias
Puncetti (1977) he said suggested that we are already 2 minds and by removing the hypothalamus we are only emphasising the difference
In contrast some researchers argue that the 2 hemispheres form a highly integrated system and are both involved in most everyday tasks
Explain the negative evaluation of split brain research: issues with generalisability
The sample of participants is unusual
Only 11 who all had a history of epileptic seizures
It has been argued that this may have caused unique changes in the brain that may have influenced the findings
Some of the patients had more of their corpus collosum removed (some had extra tissue removed removed than others
The control group was 11 people without epilepsy, this may not have been the best control group
Explain the negative evaluation of split brain research: Difference in function may be overstated
Sperry’s research lead to overemphasises and oversimplified talk about the different hemispheres
The verbal and non verbal labels can be usefully applied to summarise the difference between the 2 hemispheres
But modern day neuroscientists would argue that the actual distinction is less clear cut and much more messy
In a neurotypical brain the 2 hemispheres are in constant communication. Most of the time either hemisphere could effectively perform a task which is normally performed by the other hemisphere when required rather than the past thought of lateralisation.
What are circadian rhythms?
Circadian rhythms are biological rhythms that have a periodicity of 24 hours. Periodicity in relation to biological rhythms is the time between one peak or maximum value and the next peak or maximum value.
Give some examples of circadian rhythms?
• Sleep-waking cycle: one period of sleep and one period of waking every 24 hours
• Core body temperatures: one peak and trough every 24 hours
• Hormone production: melatonin levels peak in the dark and are at its lowest during daylight
