Non-spatial attentional effects on P1

Objective: It has been suggested that P1, the earliest endogenous visual potential, is influenced primarily by spatial location. However, we have found that attention to non-spatial visual features can affect both the latency and amplitude of this component. Methods: A series of studies are reviewed, starting with 4 using simple geometric forms, and either serial presentation of single stimuli or presentation of stimulus arrays followed by two studies using natural complex images. Results: With simple stimuli, latency and amplitude effects are seen on the P1, but differ among the paradigms, depending on the demands of the task. The data further showed a facilitation effect and that binding occurs in parallel with single feature processing. For complex stimuli we found P1 shorter to faces than inverted faces, eyes or non-face stimuli, and larger to animal than non-animal pictures. The above effects were present in children as well as in adults. Conclusions: These findings demonstrate that very early stages of processing can be modified by top-down attentional influences across a range of ages and experimental paradigms, concordant with visual processing models showing very rapid and dispersed activation with feedback at early cortical levels.