Visual transients, such as a bright flash, reduce the proportion of saccades executed around 60-125 ms after flash onset, a phenomenon known as saccadic inhibition. Across three experiments, we apply a similar time-course analysis to the amplitudes and velocities of saccades. Alongside the expected reduction of saccade frequency in the key time period, we report two perturbations of the “main sequence”, one before and one after the period of saccadic inhibition. First, saccades launched between 30 to 70 ms following the flash were hypometric, with peak speed exceeding that expected for a saccade of similar amplitude. This finding was in contrast to the common idea that saccades have passed a “point-of-no-return” around 60 ms prior to launching, escaping interference from distractors. The early hypometric saccades observed were not a consequence of spatial averaging between target and distractor locations, as they were found not only following a localized central flash (Experiment 1), but also following a spatially generalized flash (Experiment 2). Second, across experiments, saccades launched at 110 ms post-flash, toward the end of saccadic inhibition, had normal amplitude but a peak speed higher than expected for that amplitude suggesting increased collicular excitation at the time of launching. Overall, the results show that saccades that escape inhibition following a visual transient are not necessarily unaffected, but instead can reveal interference in spatial and kinematic measures.
- eye movements
- main sequence
- saccadic inhibition
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- School of Philosophy, Psychology and Language Sciences - Personal Chair of Experimental Neuropsychology
- Edinburgh Neuroscience
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