Effects of Optic Flow Speed and Lateral Flow Asymmetry on Locomotion in Younger and Older Adults: A Virtual Reality Study

Abstract

The purpose of the study is to investigate whether there are age-related differences in locomotion due to changes in presence of vision, optic flow speed, and lateral flow asymmetry using virtual reality technology. Gait kinematics and heading direction were measured using a three-dimensional motion analysis system. Although older and younger adults were affected differentially by the availability of vision, a greater dependence on optic flow information in older adults during walking was not found. Linear relations were observed between walking performance and flow speed as well as heading direction and flow asymmetry. The findings suggest that the ability to integrate optic flow information into the multimodal system for assessment of walking speed and heading direction is comparable in older and younger adults.

Effects of Parkinson’s disease on optic flow perception for heading direction during navigation

“…The observed effects of OS on lateral drift in YC and NC subjects are consistent with previous studies that found that honeybees (Srinivasan et al 1991) and humans (Chatziastros et al 1999; Chou et al 2009; Duchon and Warren 2002; Young et al 2010) steer down a hallway by equating the speed of optic flow between the left and right visual field. By contrast, in regard to DD, whereas Chatziastros et al (1999) reported veering toward the side with higher optical spatial frequency in order to equalize the number of stripes at a given optical angle during a simulated driving task, in the present study, we found a trend of veering toward the side with lower DD.…”

“…During asymmetric manipulation of the OS of the two walls, the bees flew toward the wall with slower OS, but no significant veering occurred when optical spatial frequencies of the gratings were different between walls. Veering toward the side with slower OS has also been observed in humans during treadmill walking, over-ground walking, and simulated driving (Chatziastros et al 1999; Chou et al 2009; Duchon and Warren 2002; Young et al 2010). …”

“…Optic flow contains information relevant to heading direction during navigation and influences the coordination of gait (Chatziastros et al 1999; Chou et al 2009; Duchon and Warren 2002; Srinivasan et al 1991; Young et al 2010). The effectiveness of using vision to improve parkinsonian gait has been consistently reported, and motor freezing, one of the debilitating symptoms of PD, has been found to be strongly influenced by visual input (Davidsdottir et al 2005; Ehgoetz Martens et al 2013a, b; Lewis et al 2000; Mestre et al 1992; Morris et al 1994, 1996).…”

“…It is possible that the unilateral compression of one visual field results in the perception of an asymmetric optic flow speed (OS) and texture between the left and right visual fields, which could influence heading direction during navigation. For example, an asymmetry of OS between two visual field affects veering direction in honeybees and humans (Chatziastros et al 1999; Duchon and Warren 2002; Chou et al 2009; Srinivasan et al 1991; Young et al 2010). In a study by Srinivasan et al (1991), honeybees were trained to fly down the middle of a tunnel consisting of two walls with vertical, black-and-white gratings.…”

A novel optic flow pattern speeds split-belt locomotor adaptation

“…motor learning; optic flow; locomotion; adaptation VISUAL INFORMATION informs us of how our bodies move with respect to objects in our environment and enables us to modify our walking pattern accordingly. Optic flow, which involves radial expansion of the visual scene (Gibson 1950), is naturally generated as we move through our environment and contributes to our perception of self-motion (Perrone and Stone 1994), helps us navigate toward targets in the environment (Berard et al 2011;Chou et al 2009;Sarre et al 2008;Warren et al 2001), and helps us to avoid obstacles (Sun et al 1992). These studies highlight the fact that visual information is naturally used to modify our walking pattern and represent a potential sensory pathway that could be targeted to selectively elicit changes in locomotor coordination.…”