Hemispheric lateralisation and split-brain research

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not if object shown to LVF (RH) (said 'nothing there') :: messages from RH x relayed to language centres in LH Could select matching object out of sight using left hand (RH), able to select object most closely associated If a pinup picture was shown to LVF → emotional reaction (e.g. a giggle) but usually reported seeing nothing/just a flash of light →shows how certain functions are lateralised in brain, support view that LH is verbal and RH is 'silent' but emotional Left visual field Right visual field Visual cortex EVALUATION *LATERALISATION IN THE CONNECTED BRAIN: - Hemispheric lateralisation is a feature of both connected brain and split-brain Gereon Fink et al. (1996) used PET scans to identify active brain areas during visual processing task O When asked to attend to global elements of an image: more active regions of RH o When required to focus on finer detail: specific areas of LH dominate *ONE BRAIN: Research suggests people do not have a dominant side of brain which creates a different personality →x right- or left-brained people O Jared Nielsen et al. (2013) analysed brain scans from over 1000 people aged 7-29 ■ People used certain hemispheres for certain tasks (lateralisation), but no evidence of dominant side LATERALISATION VERSUS PLASTICITY: Lateralisation is first preference but plasticity is more important Lateralisation: adaptive, enables multitasking - Lesley Rogers et al. (2004): only chickens with lateralised brain could find food while watching for predators Neural plasticity could be seen as adaptive O Research: functions can be taken over by non-specialised areas in opposite hemisphere after damage Language can 'switch sides' as brain adapts (Holland et al. 1996) *RESEARCH SUPPORT: Research supports Sperry's earlier findings that 'left brain' and 'right brain' are distinct Michael Gazzaniga (Luck et al. 1989) showed split-brain participants perform better than connected controls on certain tasks o Faster at identifying odd object from similar ones Normal brain: LH's better cognitive strategies are interrupted by RH ETHICS: *GENERALISATION ISSUES: - Causal relationships are hard to establish Behaviour of Sperry's split-brain participants compared to neurotypical control group o X participants had epilepsy (confounding variable) O Differences between two groups may be result of epilepsy than split brain Operation not performed for purpose of research →x deliberately harmed O Participants not harmed, all procedures explained + full informed consent (voluntary) Possible that trauma of operation meant patients did not later fully understand implications of what they were agreeing to Subject to repeated testing over lengthy period, may be stressful Suggests negative consequences associated with patients' involvement → unethical?