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 (MICCN), Monash University, Melbourne, VIC 3806, Australia.
- 3Department of Biomedical Engineering, City College of the City University of New York.
- 4School of Electrical and Electronic Engineering, University College Dublin, Dublin 4, Ireland.
- Corresponding author: Gerard Loughnane, Address: Trinity College Institute of Neuroscience and School of Psychology, Trinity College Dublin, Dublin 2, Ireland, Email: loughnag{at}tcd.ie; Phone: +3531 896 4543
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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 800ms) change onset predicts slower reaction times, and that 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 that 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 towards 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 behaviour 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.
Footnotes
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The authors declare no competing financial interests.
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This study was supported by grants from the United States National Science Foundation (BCS-1358955 to S.P.K. and R.G.O.), European Research Council (63829 to R.G.O.), and the International Research Staff Exchange Scheme (612681) of the EU 7th Framework Programme to R.G.O. The authors also thank Ana Carina Pamplona, Rafael Abe, and Marco Tulio Ramalho Zoratti for help with data collection.
- Received August 18, 2017.
- Revision received December 20, 2017.
- Accepted January 14, 2018.
- Copyright © 2018 the authors
