Three methods to elicit sigma-optokinetic nystagmus in Java monkeys.

Area of Science:

• Neuroscience
• Ophthalmology
• Primate Vision

Background:

• Sigma-optokinetic nystagmus (sigma-OKN) is a visually induced eye movement.
• Understanding sigma-OKN in non-human primates can provide insights into human visual-motor control.

Purpose of the Study:

• To investigate the elicitation and properties of sigma-optokinetic nystagmus (sigma-OKN) in awake Java monkeys (Macaca fascicularis).
• To compare sigma-OKN characteristics between monkeys and humans.

Main Methods:

• Eliciting sigma-OKN using stroboscopic illumination of stationary visual patterns (stripes, dots).
• Employing postrotatory nystagmus, optokinetic afternystagmus (OKAN), and phi-movement transitions to induce sigma-OKN.
• Quantifying the average angular speed (Ve) of sigma-OKN slow phases in relation to flash frequency (fs) and spatial pattern period (Ps).

Main Results:

• Sigma-OKN was successfully elicited in Java monkeys using various methods.
• Monkey sigma-OKN shares properties with human sigma-OKN.
• A notable difference is the presence of a long-lasting sigma-OKAN in darkness in monkeys, absent in humans.
• The average angular speed (Ve) followed the equation Ve = k.Ps.fs, with k approximately 1.

Conclusions:

• Java monkeys exhibit sigma-OKN with characteristics similar to humans, particularly regarding the relationship between eye speed, spatial pattern, and flash frequency.
• The long-lasting dark sigma-OKAN in monkeys represents a significant interspecies difference in post-stimulus visual-vestibular processing.
• These findings contribute to comparative neurophysiology and our understanding of visual-motor systems.