Lateralisation and split-brain research

2 halves of brain not exactly alike. Each hemisphere functional specilisations.  Left language + speech, right visual-mtor tasks.

2 hemispheres connected. Allows info received by 1 hemisphere to be sent to other hemisphere through connecting bundles of nerve fibres eg corpus callosum

Chance to investigate diff abilities came about when in treatment for severe epilepsy, surgeons cut bundle of nerve fibres formed corpus callosum. Aim to prevent violent electrical activity accompanies epileptic seizures from 1 hemisphere to another. Patients underwent this surgery - split-brain research.

Split-brain research. Studies hemispheric lateralisation.

Took adv of fact info from left visual field goes to right hemisphere + opp. B/c corpus callosum cut in split-brain patients, info presented to 1 hemisphere no way of travelling to other hemisphere, only way of travelling to other hemisphere + can be processed only in hemisphere received it. Would fixate on dot in centre of screen while info presented to left/right visual field. Asked to make responses w/ left/right hand, or verbally (left hemisphere) w/o seeing what hands doing.

Info from left field processed by right hemusphere, but has no language centre, can't verbally respond. 

Discovered diffs b/ween hemispheres:
 - left responsible for speech + language
 - right responsible for visual-spatial processing + facial recognition.

Not shown that brain organised into regions w/ specific sections for specific tasks. Suggest connectivity b/ween diff regions as important as op of diff parts.

Main adv of laterlisation - increases neural procesing capacity. Leaves other hemisphere free to engage in another function.

Architects + mathematically gifted tend to have superior right-hemispheric skills, but also more likely to suffer higher rates allergies + problems w/ immune system - same genetic processes -> lateralisation may also effect development of immune system.

Split-brain rarely carried out now - Andrewes (2001) many studies w/ 3 patients or even only 1 - conclusions not necessarily valid.

Gazzaniga (1998) - discories from split-brain disconfirmed by more recent theories - eg JW developed capacity to speak out of right hemisphere, result JW can now speak about info present to left/right area of brain.

Lateralisation changes w/ age - found language becomes more lateralised to left hemisphere w/ increasing age in children, after 25, lateralisation decreased w/ each decade of life.