Research ReportDifferentiation of perceptual and semantic subsequent memory effects using an orthographic paradigm

This study aimed to differentiate perceptual and semantic encoding processes using subsequent memory effects (SMEs) elicited by the recognition of orthographs of single Chinese characters. Participants studied a series of Chinese characters perceptually (by inspecting orthographic components) or semantically (by determining the object making sounds), and then made studied or unstudied judgments during the recognition phase. Recognition performance in terms of d-prime measure in the semantic condition was higher, though not significant, than that of the perceptual condition. The between perceptual-semantic condition differences in SMEs at P550 and late positive component latencies (700-1000 ms) were not significant in the frontal area. An additional analysis identified larger SME in the semantic condition during 600-1000 ms in the frontal pole regions. These results indicate that coordination and incorporation of orthographic information into mental representation is essential to both task conditions. The differentiation was also revealed in earlier SMEs (perceptual>semantic) at N3 (240-360 ms) latency, which is a novel finding. The left-distributed N3 was interpreted as more efficient processing of meaning with semantically learned characters. Frontal pole SMEs indicated strategic processing by executive functions, which would further enhance memory.

► We report perceptual and semantic encoding using same stimuli with comparable tasks. ► Differential P2 indicated attention allocated for encoding of perceptual features. ► Differential N3 indicated more efficient processing of meaning. ► Coordination and incorporation into mental representation were essential to tasks. ► Strategic processing shown by frontal pole SMEs further enhanced memory.