Antagonistic Interactions Between Microsaccades and Evidence Accumulation Processes During Decision Formation
- Gerard M. Loughnane1,
- Daniel P. Newman2,
- Sarita Tamang3,
- Simon P. Kelly3,4, and
- Redmond G. O'Connell1
- 1Trinity College Institute of Neuroscience and School of Psychology, Trinity College Dublin, Dublin 2, Ireland,
- 2School of Psychological Sciences and Monash Institute for Cognitive and Clinical Neurosciences, Monash University, Melbourne, Victoria 3806, Australia,
- 3Department of Biomedical Engineering, City College of the City University of New York, New York, New York 10031, and
- 4School of Electrical and Electronic Engineering, University College Dublin, Dublin 4, Ireland
-
Author contributions: G.M.L., S.T., and S.P.K. designed research; G.M.L. and S.T. performed research; G.M.L., D.P.N., S.P.K., and R.G.O. analyzed data; G.M.L., D.P.N., S.P.K., and R.G.O. wrote the paper.
Abstract
Despite their small size, microsaccades can impede stimulus detections if executed at inopportune times. Although it has been shown that microsaccades evoke both inhibitory and excitatory responses across different visual regions, their impact on the higher-level neural decision processes that bridge sensory responses to action selection has yet to be examined. Here, we show that when human observers monitor stimuli for subtle feature changes, the occurrence of microsaccades long after (up to 800 ms) change onset predicts slower reaction times and this is accounted for by momentary suppression of neural signals at each key stage of decision formation: visual evidence encoding, evidence accumulation, and motor preparation. Our data further reveal that, independent of the timing of the change events, the onset of neural decision formation coincides with a systematic inhibition of microsaccade production, persisting until the perceptual report is executed. Our combined behavioral and neural measures highlight antagonistic interactions between microsaccade occurrence and evidence accumulation during visual decision-making tasks.
SIGNIFICANCE STATEMENT When fixating on a location in space, we frequently make tiny eye movements called microsaccades. In the present study, we show that these microsaccades impede our ability to make perceptual decisions about visual stimuli and this impediment specifically occurs via the disruption of several processing levels of the sensorimotor network: the encoding of visual evidence itself, the accumulation of visual evidence toward a response, and effector-selective motor preparation. Furthermore, we show that the production of microsaccades is inhibited during the perceptual decision, possibly as a counteractive measure to mitigate their negative effect on behavior in this context. The combined behavioral and neural measures used in this study provide strong and novel evidence for the interaction of fixational eye movements and the perceptual decision-making process.
- Received August 18, 2017.
- Revision received December 20, 2017.
- Accepted January 14, 2018.
- Copyright © 2018 the authors 0270-6474/18/382163-14$15.00/0
