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Updated: Jul 31, 2025
Investigating the Deployment of Visual Attention Before Accurate and Averaging Saccades via Eye Tracking and Assessment of Visual Sensitivity
Published on: March 18, 2019
Microsaccades are directed toward the midpoint between targets in a variably cued attention task
Shawn M Willett1, J Patrick Mayo1,2
1Department of Ophthalmology, Center for the Neural Basis of Cognition, University of Pittsburgh, 15213 Pittsburgh, PA.
Abstract:
Reliable, noninvasive biomarkers that reveal the internal state of a subject are an invaluable tool for neurological diagnoses. Small fixational eye movements, called microsaccades, are a candidate biomarker thought to reflect a subject's focus of attention [Z. M. Hafed, J. J. Clark, VisionRes. 42, 2533-2545 (2002); R. Engbert, R. Kliegl, VisionRes. 43, 1035-1045 (2003)]. The linkage between the direction of microsaccades and attention has mainly been demonstrated using explicit and unambiguous attentional cues. However, the natural world is seldom predictable and rarely provides unambiguous information. Thus, a useful biomarker must be robust to such changes in environmental statistics. To determine how well microsaccades reveal visual-spatial attention across behavioral contexts, we analyzed these fixational eye movements in monkeys performing a conventional change detection task. The task included two stimulus locations and variable cue validities across blocks of trials. Subjects were adept at the task, showing precise and graded modulations of visual attention for subtle target changes and performing better and faster when the cue was more reliable [J. P. Mayo, J. H. R. Maunsell, J. Neurosci. 36, 5353 (2016)]. However, over tens of thousands of microsaccades, we found no difference in microsaccade direction between cued locations when cue variability was high nor between hit and miss trials. Instead, microsaccades were made toward the midpoint of the two target locations, not toward individual targets. Our results suggest that the direction of microsaccades should be interpreted with caution and may not be a reliable measure of covert spatial attention in more complex viewing conditions.
Insights
Microsaccades, small eye movements, may not reliably indicate spatial attention in complex environments. Their direction was not correlated with attention accuracy in monkeys, suggesting caution in using them as biomarkers.
Area of Science:
- Neuroscience
- Ophthalmology
- Cognitive Science
Background:
- Noninvasive biomarkers are crucial for neurological diagnoses.
- Microsaccades, small fixational eye movements, are proposed biomarkers for attention.
- Previous studies linked microsaccade direction to attention using clear cues.
Purpose of the Study:
- To investigate if microsaccade direction reflects visual-spatial attention under variable conditions.
- To assess the robustness of microsaccades as biomarkers in complex, unpredictable environments.
- To analyze microsaccade behavior in monkeys performing a change detection task with varying cue validity.
Main Methods:
- Monkeys performed a change detection task with two stimulus locations and variable cue validities.
- Tens of thousands of microsaccades were analyzed.
- Microsaccade directions were compared between cued locations and between successful/unsuccessful trials.
Main Results:
- Monkeys performed well, adjusting attention based on cue reliability.
- No significant difference in microsaccade direction was found between cued locations with high cue variability.
- Microsaccades were directed towards the midpoint between targets, not individual targets, irrespective of performance accuracy.
Conclusions:
- Microsaccade direction may not be a reliable indicator of covert spatial attention in complex viewing conditions.
- The utility of microsaccades as biomarkers for attention requires careful interpretation, especially outside controlled experimental settings.
- Future research should consider the limitations of microsaccade directionality in naturalistic or complex behavioral contexts.
