Sensory and motor involvement in the enhanced redundant target effect: a study comparing anterior- and totally split-brain individuals.

This study investigated the redundant target effect (RTE) in partial split-brain (anterior section sparing the splenium), total split-brain, and neurologically intact individuals. All completed an RTE protocol in which targets were presented on the midline or in an inter- or intrahemispheric manner. Stimuli of different nature (luminance, equiluminant colour, and global motion) were used separately in three experiments in order to investigate the contribution of subcortical versus cortical pathways. Despite the preservation of the splenium (the portion of the corpus callosum assumed to transfer visual information), partial split-brain individuals showed an enhanced RTE pattern as compared to neurologically intact individuals. Total split-brain individuals showed a tendency toward larger RTEs with the luminance stimuli than with the colour and motion stimuli, whereas this was not the case for partial split-brain individuals, suggesting a contribution of the posterior portion of the corpus callosum in the RTE. It is therefore likely that both sensory and motor processes contribute to the enhanced RTE in split-brain individuals.