Mental extrapolation of motion modulates responsiveness to visual stimuli

Mental imagery is often considered to be an attentional state. We investigated whether imagining a stimulus in motion involves a corresponding movement of attention. Subjects fixating a central target extrapolated in imagery the motion of a spot that moved along a circular trajectory and then vanished. During imagery, a flash was presented with various backward and forward displacements relative to the direction of the imagined spot. Subjects had to make a saccade to the flash. Saccades were delayed by as much as 50 ms when the flash appeared displaced from the imagined spot, compared to when the flash was presented in its proximity. A similar delay in latency was obtained when subjects responded with a button press. In an "Observation" condition, in which the spot did not disappear, saccade latencies were similarly delayed, although mainly for backward flash displacements. These findings suggest that motion imagery is associated with a movement of visuospatial attention.