Functional similarities between the P1 component and alpha oscillations.

The present study attempts to demonstrate functional similarities between the P1 component of event-related potentials and alpha oscillations that are predicted by the 'alpha inhibition-timing' hypothesis. On the basis of findings showing that the frequency characteristic of the P1 component lies in the alpha range and that alpha oscillation is functionally associated with inhibition, we predict that the P1 component also reflects inhibitory processes. This hypothesis is tested in two experiments, a spatial-cuing task and a visual-semantic categorization task. The results of the cuing task demonstrate that in a similar way as alpha power, the P1 component is larger over task-irrelevant ipsilateral sites. For the categorization task, we found that the P1 component, in a similar way to alpha oscillations, is larger for task-irrelevant, distorted pictures. We conclude that the P1 component may be generated at least in part by evoked alpha oscillations and reflects inhibition in the sense of suppressing task-irrelevant processes.