Combined effects of attention and inversion on event-related potentials to human bodies and faces

We investigated effects of attentional load and inversion on event-related potentials to body or face distractors. Participants performed demanding (high load) or less demanding (low load) unrelated letter-search tasks. Bodies and faces were intact (Experiment 1) or without heads or eyes (Experiment 2). We measured prominent P100, N170, and late occipito-temporal negative (LNC) components. N170 to bodies had smaller and more anterior maxima than faces. N170 to intact bodies and faces was increased by inversion, relatively independently of load. Inversion effects were dramatically reduced for headless bodies, and even reversed for eyeless faces. Load effects were most prominent in LNC, with enhanced negativity under low load. We suggest that N170 reflects mandatory, category-specific initial distractor encoding in body- or face-sensitive cortical areas, a process which may depend on interactive encoding of hierarchical cues (bodies, heads, eyes). By contrast, LNC mainly reflects residual capacity allocated to extended processing of task-irrelevant distractors.