Saccades improve postural control: a developmental study in normal children

Abstract

Introduction: Dual-task performance is known to affect postural stability in children. This study focused on the effect of oculomotor tasks like saccadic eye movements on postural stability, studied in a large population of children by recording simultaneously their eye movements and posture.

Materials and methods: Ninety-five healthy children from 5.8 to 17.6 years old were examined. All children were free of any vestibular, neurological, ophtalmologic and orthoptic abnormalities. Postural control was measured with a force platform TechnoConcept®, and eye movements with video oculography (MobilEBT®). Children performed two oculomotor tasks: fixation of a stable central target and horizontal saccades. We measured the saccade latency and the number of saccades during fixation as well as the surface, length and mean velocity of the center of pressure.

Results: During postural measurement, we observed a correlation between the age on the one hand and a decrease in saccade latency as well as an improvement in the quality of fixation on the other. Postural sway decreases with age and is reduced in the dual task (saccades) in comparison with a simple task of fixation.

Discussion - conclusion: These results suggest a maturation of neural circuits controlling posture and eye movements during childhood. This study also shows the presence of an interaction between the oculomotor system and the postural system. Engaging in oculomotor tasks results in a reduction of postural sway.

Figure 1. Eye movements executed during postural task for the five groups of subjects.

Figure 1A: Mean values of latency of saccades (in milliseconds) during postural task. Vertical bars indicate the standard error. Asterisks indicate that the value is significantly different (p<0.003). Figure 1B: Mean values of number of saccades during fixation during postural task. Vertical bars indicate the standard error. Asterisks indicate that the value is significantly different (p<0.02).

Figure 2. Postural parameters recorded during fixation and saccades for the five groups of subjects.

Figure 2A: Mean values of the surface of the CoP (in mm²) during fixation and saccades. Vertical bars indicate the standard error. Asterisks indicate that the value is significantly different (p<0.05). Figure 2B: Mean values of the length of the CoP (in mm) during fixation and saccades. Vertical bars indicate the standard error. Asterisks indicate that the value is significantly different (p<0.02). Figure 2C: Mean values of the mean speed of the CoP (in mm/s) during fixation and saccades. Vertical bars indicate the standard error. Asterisks indicate that the value is significantly different (p<0.03).