Lateralisation and split - brain research Flashcards
What is the hemispheric lateralisation?
Refers to the fact that the two halves of the human brain aren’t exactly alike.
Mental processes in the brain are mainly specialised to either the left or right hemisphere.
How is info collected in the left hemisphere transferred to the right hemisphere?
The two hemispheres are connected through the corpus callosum.
This allows info received by one hemisphere to be sent to the other.
How was the corpus callosum investigated?
Treatment for severe epilepsy - surgeons cut the bundle of nerve fibres that formed the corpus callosum.
The aim of the procedure was to prevent the violent electrical activity that accompanies epileptic seizures form crossing from one hemisphere to the other.
AO3 Laterisation - increases neural processing capacity
Strength
By only using one hemisphere to engage in a particular task (e.g. language or mathematical ability) this leaves another hemisphere free to engage in another function.
Very little empirical evidence has been provided to show that lateralisation confers any advantage to the functioning of the brain in humans.
Rogers et al. (2004) found that in domestic chicken, brain lateralisation is associated with an enhanced ability to preform two tasks simultaneously - finding food + being vigilant for predators.
AO3 - Lateralisation changes with age
Lateralisation of function doesn’t appear exactly the same throughout an individual’s life, but changes with normal ageing.
Lateralised patterns found in younger individuals tends to switch to bilateral patterns in healthy older adults.
Why this is is unknown nut one possibility is that using the extra processing resources of the other hemisphere may in some way compensate for age related declines in function.
What is split brain research?
Research that studies individuals who have been subjected to the surgical separation of the two hemispheres of the brain as a result of severing the corpus collosum.
Who were the first psychologists to study split - brain research + in what year?
Sperry + Gazzaniga
1967
What was the study into split - brain research called and what was the aim of the research?
Hemispheric lateralisation
To test the capabilities of the separated hemispheres.
How did split - brain research work?
Info. from the left visual field goes to the right hemisphere + info. from the right visual field goes to the left hemisphere because the corpus collosum is severed there’s no way for info to travel from one hemisphere to another + info. can only be processed in the hemisphere that received it.
Give an example of split - brain research.
Patient flashed a pic of a dog to the right visual field+ were asked what they had seen.
They would answer ‘dog.’
However if a pic of a cat was was flashed to the left visual field the patient would say that they didn’t see anything.
This is because the info. from the left visual field is processed by the right hemisphere but has no language centre, so can’t respond verbally .
The left hemisphere does have a language centre + doesn’t receive info, about seeing the pic of the cat + therefore, can’t say that they’ve seen it.
What did Sperry + Gazzinga (1967) discover?
They ere able to send visual info. to just one hemisphere at a time.
What were the findings of split - brain research?
There’s a no. of differences between the two hemispheres.
The brain isn’t organised into discrete regions with specific sections responsible for specific tasks but suggests that the connectivity between the different regions is as important as the operation of the different parts.
AO3 - Limitations of split brain research
Andrewes (2001)
Split - brain research is rarely carried out with some procedures having as few as 3 ppts and some using only 1.
Andrewes claims that in some instances conclusions have been drawn from the individuals who either have a confounding physical disorder which made the split - brain procedure necessary or have had a less complete sectioning of the two hemispheres that was originally believed.
Patients who’ve had this procedure without these confounding factors are rarely encountered for in sufficient numbers to be useful for the research.
