ERP components in category matching tasks.

The current experiment attempts to investigate (1) the effect of semantic information on the ERP correlate of visual short-term memory (VMP) and (2) the utilizing of the ERP as an objective investigative tool for the clinical observation of the existence of category-specific brain systems. Event-related potentials (ERPs) were recorded from 61 locations on the scalp of 39 healthy adults in a category (either animals or fruits/vegetables) match/non-match S1-S2 paradigm. The ERPs revealed a substantially smaller amplitude for the category matching than for non-matching pictures at the posterior brain regions, with greater activation of temporo-occipital brain regions changing from the right hemisphere at first to the left hemisphere later, as demonstrated by the current source density (CSD) maps. The ERPs elicited by the category of animal were larger than the vegetable category, similarly, the animal-animal matching condition elicited larger ERPs than did the vegetable-vegetable matching condition. In addition, the topographic distribution of the vegetable-elicited ERPs revealed additional involvement of the right frontal cortex which was absent in the topographic distribution of the animal-elicited ERPs. The spatial pattern of the VMP possesses features specific to semantic processing, and the ERPs differentiate the animal category from the vegetable category, suggesting an objective on-line method to investigate the category-specific information processing among brain-damaged patients.