split brain

  • The corpus callosum is the communication pathway between the hemispheres

  • Ecliptics who aren’t finding success with using drugs to control their symptoms can have their CC cut so that epilepsy will be contained in one hemisphere

  • This reduces the number of fits suffered as hemispheres can rebound off each other to prompt seizures, it also reduces severity of seizures since they only happen in 1 side of the brain

  • However, severing communication between hemispheres has effects on behaviour and perception

sperry

  • Aim: investigate hemisphere de-connection and show how hemispheres have different functions

  • Procedure: 11 split brain patients, 11 in control group. Their performance in tasks were investigated

    • For example, participants blindfolded in one eye, asked to fixate on the centre of the screen where an image was projected on either the right or left side of the screen for 1/10 of a second that they were asked to name

  • Results: language is processed in LH, so when stimulus was presented in LVF (controlled by RH), they couldn’t name the stimulus since their brain could no longer transfer information to the other side. If image was presented in one visual field and then in the other, the participant responded like they’d never seen it

  • Conclusion: supported lateralisation

Sperry documented other effects of functioning in split brain patients:

  • Unfamiliar functions such as stringing beads on a thread could not be performed

  • Familiar situations like tying shoelaces could still be done

    • Suggests procedural memories are linked to both hemispheres

  • Some patients compensate lack of connectivity by turning their heads so both hemispheres can take in the environment

Evaluations:

  • Evidence for lateralisation/localisation

    • Experimental and control conditions establish cause and effect between CC connection and performance

    • High internal validity

  • Some extraneous variables not controlled

    • 11 split brain patients lumped together, some had experienced more de-connection than others and the amount of time they spent in drug therapy could have effects as well

    • Lowers internal validity

  • Further contradictory evidence suggests brain lateralisation doesn’t exist

    • If brain had completely task-specific areas, then plasticity wouldn’t be possible

    • EB case study who regained language abilities after LH removal

    • Implies there isn’t localisation like Sperry’s research suggests

  • Low ecological validity

    • Unlikely to be a real life situation as split brain patient would be able to compensate, unlike the research where they couldn’t switch visual fields

    • Not applicable