Eyes on hold: motion task difficulty jointly delays microsaccade and pupil responses

Area of Science:

• Neuroscience
• Cognitive Psychology
• Vision Science

Background:

• Microsaccades and pupil dynamics show consistent temporal patterns related to perception and cognition.
• Microsaccades are usually inhibited before expected stimuli and then rebound.

Purpose of the Study:

• To examine how task difficulty influences the timing of microsaccades and pupil dilation during a motion perception task.
• To test if difficulty jointly delays microsaccade rebound and peak pupil dilation.

Main Methods:

• Human participants discriminated motion direction under varying difficulty levels (cardinal vs. oblique motion, large vs. small tilt offsets).
• Recorded and analyzed microsaccade rates and pupil dilation responses.

Main Results:

• Higher task difficulty intensified and extended microsaccade inhibition, delaying rebound.
• More difficult conditions showed larger amplitude and delayed peak pupil dilation.
• Response times correlated with microsaccade rebound and peak pupil dilation timing.

Conclusions:

• Delayed microsaccade rebound and pupil responses indicate prolonged sensory evidence accumulation.
• The synchronized temporal dynamics suggest a shared neural basis for pupil and microsaccade control.