Optokinetic and vestibulo-ocular reflex responses to an unpredictable stimulus

Area of Science:

• Neuroscience
• Ophthalmology
• Vestibular System

Background:

• The vestibulo-ocular reflex (VOR) stabilizes gaze during head movements.
• The optokinetic reflex (OKR) uses visual stimuli to stabilize gaze.
• Understanding the interplay between VOR and OKR is crucial for gaze control.

Purpose of the Study:

• To investigate horizontal plane optokinetic (OKR) and vestibulo-ocular reflex (VOR) eye movements.
• To characterize OKR gain and phase across a range of frequencies.
• To explore interactions between visual and vestibular motion information and their effect on eye movements.

Main Methods:

• Collected OKR and VOR data from normal subjects using pseudorandom rotational stimulation.
• Analyzed eye movement responses across frequencies from 0.02 Hz to 1.5 Hz.
• Assessed incidence of motion sickness induced by optokinetic and vestibular stimulation.

Main Results:

• Large intersubject variability was observed in OKR responses.
• OKR gain remained relatively constant (mean 0.65) from 0.02-1.5 Hz.
• Phase lags increased with frequency, indicating time delays (mean 180 ms).
• Visual motion information significantly influenced eye movements up to 6.1 Hz.
• Optokinetic stimulation induced motion sickness in ~20% of subjects, while vestibular stimulation did not.

Conclusions:

• Visual motion information plays a significant role in eye movement control.
• The OKR exhibits frequency-dependent phase lags, suggesting neural processing delays.
• Optokinetic stimulation, but not vestibular stimulation, can induce motion sickness.