Characteristics of motion perception in infantile nystagmus syndrome

- An examination of a horizontal INS patient-

Abstract

Perception of coherent motion is important for understanding the direction of everyday motion, but how coherent motion sensitivity changes with direction and velocity in Infantile Nystagmus Syndrome (INS) remains unclear. This study aimed to clarify the effects of direction and velocity on coherence thresholds using RDK in one INS patient and 10 healthy controls. Results showed a horizontal advantage in the healthy control group, with no effect of velocity. In contrast, in INS, a vertical advantage was consistent across all velocity, with thresholds decreasing with increasing velocity, and the decrease was greater in the horizontal direction. This result suggests that horizontal motion cues, unique to INS, are obscured by retinal image fluctuations. Although this study does not represent the overall INS population because N = 1, the results support the idea that direction discrimination sensitivity differs between INS and healthy controls.