Task effects on event-related potentials to single letters and pseudoletters

Abstract Previous event-related potentials (ERP) studies examining of orthographic processing have reported N1 results that are incompatible with one another, some reporting larger N1 responses to letters and some reporting larger and broader N1 responses to pseudoletters. Conflicting results may be due to different tasks, which required different cognitive demands and thus resulted in different ERPs. Our study compared the ERPs of 20 participants across three different tasks: mixed viewing of letters and pseudoletters, blocked viewing of letters and pseudoletters, and 1-back memory tasks. We evaluated the timing, amplitude, and hemispheric dominance/laterality of the early ERP components (e.g., N1) to letter and pseudoletter stimuli. Results showed the same significant ERP differences between letters and pseudoletters across all tasks. This indicated that letter processing may be independent of the tasks employed and that the early ERPs for orthographic processing appear not to be not altered by volitional control or task demands used in this study.