Optic flow dominates visual scene polarity in causing adaptive modification of locomotor trajectory

Abstract

Locomotion and posture are influenced and controlled by vestibular, visual and somatosensory information. Optic flow and scene polarity are two characteristics of a visual scene that have been identified as being critical in how they affect perceived body orientation and self-motion. The goal of this study was to determine the role of optic flow and visual scene polarity on adaptive modification in locomotor trajectory. Two computer-generated virtual reality scenes were shown to subjects during 20 minutes of treadmill walking. One scene was a highly polarized scene while the other was composed of objects displayed in a non-polarized fashion. Both virtual scenes depicted constant rate self-motion equivalent to walking counterclockwise around the perimeter of a room.Subjects performed Stepping Tests blindfolded before and after scene exposure to assess adaptive changes in locomotor trajectory. Subjects showed a significant difference in heading direction, between pre and post adaptation stepping tests, when exposed to either scene during treadmill walking. However, there was no significant difference in the subjects' heading direction between the two visual scene polarity conditions. Therefore, it was inferred from these data that optic flow has a greater role than visual polarity in influencing adaptive locomotor hnction. 2

Age-related deficits of dual-task walking: The role of foot vision

“…The crucial role of visual demand for ARD could be related to the fact that already single-task walking requires substantial visual processing, since we need to navigate through visually defined space [10][11][12]. Thus, ARD seem to reflect seniors' problems to concurrently process two streams of visuo-spatial information, one related to walking and the other to a visual non-walking task.…”

Strategies of healthy adults walking on a laterally oscillating treadmill

“…Human ability to adjust gait patterns has been explored with manipulations of optic flow, body loading, and the support surface, and each modality has been successful in inducing adaptive locomotor changes [1][2][3][4][5][6][7][8][9]. Subjects who walked on a treadmill while viewing immersive, rotating visual scenes showed adaptive changes both during their exposure and during post-exposure testing [5,6,8].…”

“…Subjects who walked on a treadmill while viewing immersive, rotating visual scenes showed adaptive changes both during their exposure and during post-exposure testing [5,6,8]. Prokop et al showed that optic flow modulates a selfselected walking velocity and suggested that an individual's strategy to stabilize walking velocity depends on the way information is weighted from different afferent sources [7].…”

Effects of a dual-task training on dynamic and static balance control of pre-frail elderly: a pilot study

“…With increasing age, individuals seem to rely more on exteroceptive information and prioritize the use of vision to control the balance (4), so a de icit would directly affect the movement, since the stability and body position are constantly adjusted by optical low and positioning cues (5).…”