Background: In this study Roger Sperry investigated the functions of separated hemispheres of the human brain. The experiments were undertaken on people who had already had their corpus callosum severed as treatment for severe epilepsy. Human brains are divided into hemispheres – a left hemisphere and a right hemisphere. Although these halves look similar they have very different functions. This division of tasks between the hemispheres is called lateralisation of function. For example, the major functions of language are carried out in the left hemisphere (for right handed people). The table below gives a summary of some of the functions you need to know for this study. The hemispheres are joined at their base by commissural fibres, which allow the hemispheres to communicate internally. The commissural fibres are bundled into structures called commissures (these include the corpus callosum). These fibres are sometimes cut by surgeons to reduce the effects of epilepsy.