The time course of visual categorization: Electrophysiological evidence from ERP

Visual categorization can be derived from interaction between inputting features set (IFS) from outside stimuli and anticipating features set (AFS) from concept, and such interaction can take two forms: match extraction and conflict control. Using ERP recording, we investigated the temporal course of visual categorization. The results indicated that the larger the AFS, the higher the amplitude of the N1 was generated, which demonstrated the effect of the AFS on the attention. When the size of the AFS was larger than or equal to 2, prominent N2 component was elicited, which demonstrated the effect of conflict when the feature of IFS mismatched with the feature of the AFS. The judgment of category was manifested on the LPC component, and this component was also sensitive to conflict control. Based on the results, we proposed that the temporal course of visual categorization was as follows: selective attention, feature perception, feature match/extraction and judgment of category/conflict control. Among those processes, the judgment of category is the core processing; however the former three sub-processes form the base of categorization. The results are in support of the idea that LPC is responsible for high-level categorization process.