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Colas Authié, Alain Berthoz, José-Alain Sahel, Avinoam B Safran; Locomotor reproduction of memorized trajectories: where peripheral vision matters. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5033.
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© ARVO (1962-2015); The Authors (2016-present)
During locomotion, we spontaneously anticipate our locomotor trajectory by head and gaze direction. This behavior is important to select visual information, simulate the future trajectory and stabilize the perception of space. However, in retinitis pigmentosa (RP), the loss of peripheral visual field (VF) leads to adaptive changes in sensory-motor coordination. Our objective is to determine whether theses adaptations can alter the usual gaze anticipation behavior, and therefore the trajectory execution.
Eight RP subjects presenting a VF limited to central 10-22° (diam.) and eight control subjects were asked to walk along two trajectories, previously shown on a sheet of paper (see Fig1.A). Whole body kinematics (Vicon, 120 Hz) and eye movements (Mocaplab eye-tracker, 60 Hz) were captured. Dependent variables include trajectory geometry (Fig1.C), walking speed, stepping parameters (Fig1.D), head and gaze anticipation (Fig1.B) and percentage of reverse-saccades (quick eye movements in the direction opposite to the path).
Although no significant difference between groups was found in trajectory size, closing error was larger in RPs than in controls (Tab1). The walking speed was also reduced in RP group. No difference between groups was observed in all stepping parameters. On average, anticipatory eye and head movements in RP subjects were similar to those of controls. However, affected subjects demonstrated a larger proportion of reverse-saccades, leading to a sequence of back and forth gaze movements around future trajectory.
Loss of peripheral VF did not change usual anticipation behavior. However, RP patients occasionally interrupted their consistent anticipation by performing opposite rapid eye movements (reverse-saccades), presumably to update their postural reference frame and the egocentric distance to the planned trajectory. This behavior could be related to larger error in trajectory completion.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Fig1 A. Proposed trajectories presented to tested subjects. B. Gaze and head anticipation from pelvis heading. C. Top view of trajectory variables. D. Step parameters.
Table 1. Mean values (±SD) and statistical results. Anovas F values, significance level (p) and effect size (eta2) for each comparison are reported.
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