Right hemisphere lateralization and holistic processing do not always go together: An ERP investigation of a training study

Holistic processing (HP) and right-hemispheric lateralization both mark expertise in visual object recognition such as face and sub-ordinate object perception. However, counterexamples have been found recently: Experiences of selective attention to parts such as writing experiences in Chinese characters reduced HP while increased right hemisphere lateralization. We investigated the association between HP and brain activities measured by event-related potentials (ERP) in participants trained to recognize artificially-created scripts using either whole-word or grapheme-to-phoneme approaches. Stronger N170 activities were found in both hemispheres in both training approaches. Though the type of training approaches induced opposite directions in correlations between HP and the ERP signals in the right hemisphere: In the whole-word condition, the HP effect increased with stronger right-hemispheric N170 activities; while the direction of this correlation was reversed in the grapheme-to-phoneme condition. This demonstrates that HP and right hemispheric lateralization are separate processes that are associated with different perceptual mechanisms.