Introduction to Special Thematic Issue, part 2 "Microsaccades: Empirical Research and Methodological Advances"

Area of Science:

• Oculomotor control and cognitive neuroscience
• Visual perception and psychophysics
• Clinical eye movement analysis

Background:

• Microsaccades bridge basic oculomotor control and complex cognition.
• Their role in sensory, perceptual, and cognitive processes is an active research area.
• Understanding microsaccades is challenged by experimental subtlety and statistical analysis.

Purpose of the Study:

• To investigate pupillary and microsaccadic responses during complex decision-making under affective priming.
• To examine microsaccade signatures under monocular and binocular stimulation for clinical applications.
• To analyze microsaccades during high-speed visual search and their perceptual functions.
• To explore the torsional component of microsaccades and their behavior during optokinetic stimulation.
• To determine the relationship between task difficulty (visual vs. mental load) and microsaccade rate.

Main Methods:

• Pupillometry and eye-tracking during multi-attribute decision-making with affective priming.
• Eye-tracking during fixation on Gabor patches under monocular and binocular conditions.
• High-speed eye-tracking during visual search for targets in cluttered and simple backgrounds.
• Three-dimensional eye-tracking during fixation and optokinetic stimulation.
• Eye-tracking and performance data collection during a continuous performance task (n-back) with manipulated visual and mental load.

Main Results:

• Microsaccadic rate inhibition and pupillary dilation occurred with cognitive effort, modulated by affective priming; aversive priming amplified responses.
• Microsaccadic rate signatures correlated between monocular and binocular stimulation, suggesting clinical utility.
• Microsaccade rate dropped to near zero during high-speed visual search, with some occurring post-saccade, suggesting perceptual roles.
• Torsional microsaccade components were recorded, correlating with horizontal components; optokinetic stimulation induced larger, more frequent torsional quick phases.
• Increased microsaccade rate was linked to high visual load (abstract figures) but not mental load (n-back level).

Conclusions:

• Pupillary responses are more sensitive to affective priming than microsaccadic rate.
• Microsaccade rate signatures are robust across different stimulation conditions, supporting clinical applications.
• Microsaccades can serve perceptual functions during continuous visual search.
• The torsional component of microsaccades is significant and behaves differently under stimulation.
• Microsaccade rate primarily reflects the visual load of a task, not its mental load.