PURPOSE: Microsaccades have been associated with a variety of functions such as eliminating visual fading, supporting detailed visual search, indicating covert attention and in?uencing motor preparation. Although the direction of microsaccades could be modulated by the spatial location of covert attention, there is no elaborate study about the change of microsaccades direction along time.
METHODS: Two monkeys were trained to perform two spatial choice tasks in which the monkeys needed to ?gure out one from two stimuli as saccadic goal based either on the spatial location of a visual cue or the color of stimuli.
RESULTS: The direction of microsaccades of two monkeys began to rotate shortly after the onset of the cue (spatial or color) and continued until a response saccade was allowed in both tasks. The speed of the rotation of microsaccades direction di?ered between two di?erent saccade choices. In contrast, no rotation of microsaccades direction was observed in a memory guided saccade task in which no competing choice was provided.
CONCLUSIONS: The rotation of microsaccades direction in spatial choice tasks represents the motor choice of monkeys. In addition, this rotation phenomenon of microsaccades might indicate that the mental process conducting a saccade response from a saccade choice is continuous rather than saltatory.