Saccades to mentally rotated targets.

In order to investigate the role of mental rotation in the directional control of eye movements, we instructed subjects to make saccades in directions different from that of a visual stimulus (rotated saccades). Saccadic latency increased linearly with the amount of directional transformation imposed between the stimulus and the response. This supports the hypothesis that reorienting a saccade is accomplished through a mental rotation process. No differences were found in amplitude, duration, velocity, and curvature between rotated and visually guided saccades. Analogous to mental rotation tasks involving reaching arm movements, it is surmised that frontal/prefrontal cortical structures participate in rotated saccades by reorienting the intended saccadic direction. A linear increase in response time with the imposed directional transformation was also found in an analogous mental task not requiring a directed motor response, namely, mentally localizing a point in space at a certain angle from a stimulus direction. However, the speed of mental rotation was systematically lower than in the rotated saccade task. These findings indicate that mental rotation is a rather general mechanism through which directional transformations are achieved.