Effects of selective attention on the C1 ERP component: A systematic review and meta‐analysis

Abstract The C1 event‐related potential (ERP) captures the earliest stage of feedforward processing in the primary visual cortex (V1). An ongoing debate is whether top‐down selective attention can modulate the C1. One side of the debate pointed out that null findings appear to outnumber positive findings; thus, selective attention does not seem to influence the C1. However, this suggestion is not based on a valid approach to summarizing evidence across studies. Therefore, we conducted a systematic review and meta‐analysis investigating the effects of selective attention on the C1, involving 47 experiments and 794 subjects in total. Despite heterogeneity across studies, results suggested that attention has a moderate effect on the C1 (Cohen's = 0.33, p < .0001); that is, C1 amplitude is larger for visual stimuli that are attended than unattended. These results suggest that C1 is affected by top‐down selective attention.