Visuomotor mental rotation of saccade direction

This investigation studied the latencies of saccadic eye movements that were directed away from a target by a variable angular distance, which was given by instruction. Such a movement presumably requires an intentional, visuomotor mental rotation of the saccade vector, resulting in prolonged reaction times. From a study on the control of directed hand movements, it has been hypothesized that all visuomotor and visual mental rotation tasks share a common processing stage. We tested this hypothesis with a saccade task in which subjects shifted their gaze either towards (0 degrees, pro-saccade), or 30, 60, 90, 120, 150, or 180 degrees(anti-saccade) away from a randomly cued position on an imaginary clock face. With four different cueing conditions, latencies increased monotonically with required gaze shift from 0-150 degrees, thus exhibiting a mental rotation latency pattern. However, we also found anti-saccades faster than 150 degrees gaze shift and slower rotation speeds with peripheral cues than with central cues. Together with the overall shallower latency increase compared with previous findings with mental rotation tasks, these results cast doubt on the notion of a common, central processing mechanism for the different types of tasks.