Temporal dynamics of saccades explained by a self-paced process

Sci Rep. 2017 Apr 20;7(1):886. doi: 10.1038/s41598-017-00881-7.

Abstract

Sensory organs are thought to sample the environment rhythmically thereby providing periodic perceptual input. Whisking and sniffing are governed by oscillators which impose rhythms on the motor-control of sensory acquisition and consequently on sensory input. Saccadic eye movements are the main visual sampling mechanism in primates, and were suggested to constitute part of such a rhythmic exploration system. In this study we characterized saccadic rhythmicity, and examined whether it is consistent with autonomous oscillatory generator or with self-paced generation. Eye movements were tracked while observers were either free-viewing a movie or fixating a static stimulus. We inspected the temporal dynamics of exploratory and fixational saccades and quantified their first-order and high-order dependencies. Data were analyzed using methods derived from spike-train analysis, and tested against mathematical models and simulations. The findings show that saccade timings are explained by first-order dependencies, specifically by their refractory period. Saccade-timings are inconsistent with an autonomous pace-maker but are consistent with a "self-paced" generator, where each saccade is a link in a chain of neural processes that depend on the outcome of the saccade itself. We propose a mathematical model parsimoniously capturing various facets of saccade-timings, and suggest a possible neural mechanism producing the observed dynamics.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Central Pattern Generators / physiology*
  • Female
  • Fixation, Ocular
  • Humans
  • Male
  • Models, Neurological*
  • Refractory Period, Electrophysiological
  • Saccades*