Task modulation of visual category selectivity at physical and conceptual levels: An ERP study

Visual perception emerges from dynamic interactions between bottom‑up sensory input and top‑down, task‑driven expectations. This study tested whether task‑related ERP modulations during object categorization depend on low‑level category‑specific features-specifically the amplitude spectrum (AS)-or whether they arise independent of these features. Participants viewed grayscale images of animals and vehicles with either intact or equalized AS, each paired with an "X" or "O." They performed either a category‑relevant task (animal vs. vehicle) or a category‑irrelevant task ("X" vs. "O"). Task demands influenced visual processing at multiple stages. P1 category selectivity emerged only for intact AS stimuli under category-relevant task demands, indicating sensitivity to low-level structure. In contrast, P2/N2 differences were present across AS and task conditions, although their magnitude was modulated, consistent with higher-level category representations. The lack of sustained early effects raises questions about how sensory evidence is transformed across processing stages. Manipulating category relevance revealed task modulation beyond response-format effects, showing how top-down goals shape both early sensory and later category-level processing as reflected in distinct visual ERP components.