Lateralisation and Split-brain Research

What is hemispheric lateralisation?

Some mental processes in the brain are mainly specialised to either the left or right hemisphere

How do we investigate the different abilities of the two hemispheres?

Split brain research which involves the surgical separation of the two hemispheres of the brain as a result of severing the corpus callosum

What are the left and right hemispheres dominant in?

*Left hemisphere* - language and speech *Right hemisphere* - visual motor tasks

Strengths of lateralisation

*Strengths* - Increases neural capacity by only using one hemisphere of the brain for certain tasks - Lateralisation has been shown to change with age as older adults have less lateralisation of function using both hemispheres. It's been found language lateralisation decreases after 25 suggesting both hemispheres are recruited to perhaps compensate for cognitive decline associated with age

What is an example of a typical outcome of split brain research?

- Normally, information that comes into the left visual field is processed in the right hemisphere and vice versa, however when the corpus callosum is split, the two hemispheres cannot connect - This means that all information coming into the right visual field, can easily be processed and spoken aloud etc, however when information comes into the left, the people couldn't say they had seen it, as the connecting tissue to the left hemisphere had be cut

Weakness of split brain research

- One case study named JW developed the ability to speak using the right hemisphere suggesting brain leteralisation is not exclusive - Split brain research is very uncommon and rarely uses more than 3 people per study meaning the conclusions could very easily be drawn from participants with confounding variables like physical disorders, affecting the validity of conclusions

What is the basis of split brain research?

- The fact that information from the left visual field goes into the right hemisphere and information from the right visual field goes into the left hemisphere - Sperry and Gazzaniga split the corpus callosum meaning all information presented to one hemisphere could only be processed in that same hemisphere

How do we use both hemispheres?

- They are connected i.e. we can use language to talk about things we see (left and right) - Connected through bundles of nerve fibres such as the corpus callosum

What did Broca establish in 1861?

Damage in a particular area of the left brain lead to language deficits yet in the same area on the right brain there were no language issues