Visuomotor mental rotation of saccade direction

This investigation studied the latencies of saccadic eye movements that wer e directed away from a target by a variable angular distance, which was giv en by instruction. Such a movement presumably requires an intentional, visu omotor mental rotation of the saccade vector, resulting in prolonged reacti on times. From a study on the control of directed hand movements, it has be en 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 randoml y cued position on an imaginary clock face. With four different cueing cond itions, latencies increased monotonically with required gaze shift from 0-1 50 degrees, thus exhibiting a mental rotation latency pattern. However, we also found anti-saccades faster than 150 degrees gaze shift and slower rota tion speeds with peripheral cues than with central cues. Together with the overall shallower latency increase compared with previous findings with men tal rotation tasks, these results cast doubt on the notion of a common, cen tral processing mechanism for the different types of tasks.