Where action impairs visual encoding: an event-related fMRI study.

Behavioral experiments revealed an impairment in a perceptual task when a motor task has to be planned in parallel. In two event-related fMRI experiments healthy participants performed a GO-NOGO motor task and a visual identification task. Thus, we were able to investigate the influence of a motor task on visual identification. The paradigm allowed to compare visually identical trials with and without a concurrently performed motor response. In Experiment 1, the visual task focused on shape identification, whereas in Experiment 2, the visual task focused on color identification. We found an action-dependent BOLD response modulation in extrastriate visual areas (V3, V3A in Experiment 1 and additionally V4 in Experiment 2). Thus, results demonstrate that the planning of an action has modulatory effects in brain areas concerned with early processes in visual encoding.