The use of auto-correlation function to quantify periodicity in smooth pursuit

Area of Science:

• Neuroscience
• Ophthalmology
• Biomedical Engineering

Background:

• Smooth pursuit eye movement is crucial for maintaining gaze on moving objects.
• Disruptions in smooth pursuit can indicate underlying neurological dysfunction.
• Quantifying eye movement periodicity is essential for assessing visual feedback control.

Purpose of the Study:

• To evaluate the utility of auto-correlation function in quantifying smooth pursuit eye movement periodicity.
• To compare smooth pursuit eye movement periodicity between healthy volunteers and patients with neurological disorders.
• To investigate potential impairments in the visual feedback mechanism of smooth pursuit in neurological conditions.

Main Methods:

• Smooth pursuit eye movements were recorded using a DC amplifier during horizontal sinusoidal target motion at frequencies from 0.3 to 1.2 Hz.
• Eye movement data were digitalized at 100 Hz with 12-bit accuracy.
• The auto-correlation function was applied to digitalized eye movements to calculate the auto-correlation coefficient, serving as a measure of periodicity.

Main Results:

• In healthy volunteers, the auto-correlation coefficient remained high (near 1.0) at 0.3 Hz and decreased with increasing target frequencies.
• Patients with neurological disorders exhibited significantly lower auto-correlation coefficients across all tested target frequencies compared to healthy controls.
• A reduced auto-correlation coefficient indicated diminished periodicity in smooth pursuit eye movements.

Conclusions:

• The auto-correlation coefficient effectively quantifies periodicity in smooth pursuit eye movements.
• Neurological disorders are associated with reduced smooth pursuit eye movement periodicity.
• Impaired visual feedback mechanisms in smooth pursuit control are suggested by decreased periodicity in patients with neurological disorders.