Rapid stimulus-driven modulation of slow ocular position drifts

Area of Science:

• Neuroscience
• Ophthalmology
• Visual Perception

Background:

• During gaze fixation, eye movements include microsaccades and slow drifts.
• Ocular drifts were largely considered random, with limited understanding of their control.
• The rapid processing of visual information by the oculomotor system remains an area of active research.

Purpose of the Study:

• To investigate whether ocular position drifts are stimulus-driven and exhibit short latencies.
• To characterize the properties of stimulus-evoked ocular drift responses.
• To explore the relationship between visual stimuli and oculomotor control during fixation.

Main Methods:

• Utilized high-precision eye tracking in three macaque monkeys.
• Presented brief visual stimuli (duration ~8 ms) to assess responses.
• Analyzed ocular position changes, specifically drifts, in response to visual input.

Main Results:

• Ocular position drifts were found to be systematically stimulus-driven with latencies around 60 ms.
• Transient, stimulus-specific modulations of drifts were observed following brief visual presentations.
• Responses were binocular, favored large, low spatial frequency stimuli, and showed pattern selectivity.
• Exclusion of confounding factors like convergence, pupil size, head, or initial eye position.

Conclusions:

• Ocular position drifts are not random but can be rapidly modulated by visual stimuli.
• This demonstrates that ocular drifts have fast access to exogenous visual information.
• The findings challenge previous notions of drift randomness and highlight a rapid visual-to-oculomotor pathway.