Abstract: C1 is the first cortical component of visual evoked potentials (VEPs). C1 modulation effect refers to the phenomenon that attention and other factors could affect the amplitude of C1. Previous studies have mainly observed modulation of the P1 and N1 components due to attention, but not of C1 component, based on which researchers have brought forward the delayed feedback hypothesis. Recent studies, however, have observed conflicting evidence that C1 may be modulated by attention, suggesting that attention may impinge on the early stage of visual information processing. Future research should investigate the impact of attention and perceptual learning on the modulation of C1 component and clarify the roles of perceptual load, attentional load, and other contributory factors as well as their interactions in generating C1 modulation effect.

Key words: C1 modulation effect, Attention, Delayed feedback hypothesis, Perceptual learning, Load theory