Biopsych: Hemispheric Lateralisation Flashcards
What is lateralisation?
The idea that the 2 halves of the brain are functionally different and that each hemi has functional specialisations, e.g. the left is dominant for language and the right excels at visual motor tasks
- the 2 hemis are connected through nerve fibres called the corpus callosum, which facilitates inter-hemispheric communications: allowing the left and right hemis to ‘talk to each other’
- split Brian patients have the corpus callosum cut, severing the link between the hemis
What was Sperry and Gazzanigas split brain research?
- study the capabilities of the separated hemis, they were able to send visual info to just one hemi at a time to study hemi lateralisation.
- they took advantage of the fact info from the left visual field goes to the right hemi and vice versa, and as the corpus callosum is cut in split brain patients, the info presented in one hemi has no way of travelling to the other- and can be processed only in the hemi it is received in.
What’s an example of a Sperry and Gazzingas study?
- e.g. if a picture of a cat flashed to the right visual field and was asked what they saw, would reply with cat. Yet if a picture of a dog flashed to the left visual field is the answer would be nothing. This is because the info from the left visual field is processed by the right hemi, which can see the picture, but as it has no language centre, cannot respond verbally. The left hemi, which does have a language centre, does not receive info about seeing the picture, therefore cannot say they have seen it.
What did this research conclude?
That the left hemi is dominant for speech and language and the right hemi is dominant for visual motor tasks
How did Rogers study the idea HL increases neural processing capacity (the ability to perform multiple tasks simultaneously)?
Rogers found that in a domestic chicken, brain lateralisation is associated with an enhanced ability to perform two tasks simultaneously (finding food whilst being vigilant for predators). Using only one hemi to engage in a task leaves the other hemi free for other functions. Therefore enhancing the efficiency in cognitive tasks.
What did Turk et al find about language not being restricted to the left hemi and this being a weakness for HL?
Turk discovered a patient who suffered damage to the left hemi but developed the capacity to speak in the right hemi, eventually leading to the ability to speak about the info presented to either side of the brain. This suggests that perhaps lateralisation is not fixed and that the brain can adapt following damage to areas.
What’s one problem with Sperrys research?
The split brain procedure is hardly carried out anymore, so split brain patients are hard to come by. Such studies often include few ptps and the research takes an idiographic approach. So any conclusions drawn are only representative to those who had a confounding physical disorder that made the procedure necessary. Results cannot be generalised to the wider population.
What’s a positive of Sperrys research?
Good controls (as a in a lab) and his method of presenting visual info to one hemi at a time was ingenious. Ptps stared at a fixed point and images were shown for 1/10th of a second, so the eye wouldn’t have time to move over the image and spread info across both visual fields and subsequently both sides of the brain, ensuring only one hemi received info at any one time. This standardised procedure meant that it had good internal validity and has produced a study was replicable.
