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Shlomit Yuval-Greenberg, Roy Amit, Izhar Bar-Gad; An orchestra without a conductor: Saccadic visual exploration can be explained by a self-paced process. Journal of Vision 2017;17(10):902. doi: https://doi.org/10.1167/17.10.902.
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© ARVO (1962-2015); The Authors (2016-present)
Background: Sensory organs are thought to sample the environment rhythmically thereby providing periodic perceptual input. Some sensing behaviors, such as rodents' whisking, are governed by central oscillatory generators 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. The temporal dynamics of saccades determine the flow of visual input and so explaining what governs them is vital for understanding vision. The purpose of the present study was to examine whether saccade properties are consistent with an oscillatory generator or whether they can be more parsimoniously explained by a self-generating first-order process. Methods: 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 using methods derived from spike-train analysis. The first- and high-order dependencies within saccade sequences were examined through a statistical interval-shuffling procedure. We tested our data against a mathematical model to demonstrate that first-order dependencies can fully account for the observed saccade dynamics. Results: The findings show that saccade timings can be fully and parsimoniously explained by a self-generating mechanism. The temporal dynamics of saccadic events are explained by first-order dependency features, and mainly by the post-saccadic inhibition period. The proposed mathematical model contains only first-order dependencies and nevertheless captures the various facets of saccade timings. Conclusion: Saccades are different than other exploratory systems, such as whisking or sniffing. Unlike those exploratory systems, which were shown to be driven by central oscillations, saccades can be more parsimoniously explained as a self-driven process. This is a first step toward examining whether saccade dynamics could be a source rather than a consequence of rhythm injected into the visual cortex.
Meeting abstract presented at VSS 2017
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