Hemisperic Laterlisation and Split-Brain Research

Hemispheric lateralisation

The idea that the two halves (hemispheres) of the brain are functionally different and control specific mental processes and behaviours.

Split-brain research

Studies examining individuals who had their corpus callosum surgically severed to treat severe epilepsy

Corpus callosum

The main bundle of nerve fibres connecting the left and right hemispheres of the brain.

Left hemisphere (LH) specialization

Acts as the "analyser" and controls speech

Right hemisphere (RH) specialization

Acts as the "synthesiser" and handles visual-spatial processing

Contralateral wiring

The neural setup where each hemisphere controls movement and receives sensory data from the opposite side of the body.

Visual field processing

Left visual field (LVF) of both eyes connects to the right hemisphere; Right visual field (RVF) of both eyes connects to the left hemisphere.

Sperry’s procedure (1968)

Projected images or words to a participant's RVF or LVF for 1/10th of a second while they focused on a central point.

RVF visual finding

When an image was presented to the RVF (processed by the LH)

LVF visual finding

When presented to the LVF (processed by the RH)

Tactile recognition task

Split-brain patients could physically select matching objects or associated items (e.g.

Emotional reaction task

Presenting a pin-up picture to the LVF caused emotional responses (like a giggle)

Fink et al. (1996) support

PET scans showed the RH is active during global visual processing (e.g.

Szaflarski et al. (2006) limitation

fMRI study showing LH dominance for language increases from ages 5–20

Rogers et al. (2004) adaptive value

Showed lateralisation allows animals (e.g.

Luck et al. (1989) research support

Found split-brain participants performed faster than connected controls at finding odd objects

Control group confound

Sperry’s neurotypical control group lacked epilepsy

Ethical considerations in Sperry's research

Participants gave informed consent and were not intentionally harmed

Kim Peek exception

A natural split-brain individual born without a corpus callosum who developed bilateral language centers