Abstract
Microsaccade inhibition has been researched extensively as indicator for the employment of attention to an eccentric target location. But, it has been found that microsaccade inhibition occurs in response to task-unrelated visual transients as well, indicating a rather low level origin of the micro-saccade rate reduction. The current study evaluates microsaccade inhibition in response to periodically occurring short-term visual transients of a fixational target. 13 subjects fixated a target for a duration of 300 seconds. Short target-off phases were applied as visual transients in sequences within defined time-intervals. After 10 seconds of steady target presentation, target-off phases of 10 ms were applied within a 3 second time interval. This sequence was applied repeatedly, summing up to an extended fixation of 300 seconds. Three different conditions were measured, in which target-off phases were applied to the fixation target at different repetition rates. In the first two conditions, target-off phases occurred regularly with repetition rates of 50 Hz and 5 Hz, respectively. In the third condition, target-off phases were applied repeatedly with random delays. After each target-off phase micro-saccade rate has been analyzed as a measure of microsaccade inhibition. Microsaccade rates dropped in response to the first visual transient but did not in the following visual transients. Only after an extended period of time, microsaccade inhibition occurred again in response to a visual transient. Differential effects were found depending on the repetition rate of the target-off phases. After microsaccade rate inhibition occurring to an initial visual transient in the fovea, microsaccade rate was “blind” to visual transients for an extended period of time, indicating higher level processing in response to exogenous visual transients at the target location.