Beyond the point of no return: Effects of visual distractors on saccade amplitude and velocity

Antimo Buonocore, Robert D. McIntosh, David Melcher

Research output: Contribution to journalArticle

Abstract

Visual transients, such as a bright flash, reduce the proportion of saccades executed, ~60–125 ms after flash onset, a phenomenon known as saccadic inhibition (SI). 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 SI. First, saccades launched between 30 and 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,” ~60 ms before 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 postflash, toward the end of SI, 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.

Original languageEnglish (US)
Pages (from-to)752-762
Number of pages11
JournalJournal of neurophysiology
Volume115
Issue number2
DOIs
StatePublished - Feb 9 2016

Keywords

  • Eye movements
  • Main sequence
  • Saccadic inhibition

ASJC Scopus subject areas

  • Neuroscience(all)
  • Physiology

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