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The Effects of Optic Flow Manipulations on Heading Direction and Gait Coordination During Over-ground Walking
Daniel Edward Young
出版
Boston University
, 2009
URL
http://books.google.com.hk/books?id=1eL2ZwEACAAJ&hl=&source=gbs_api
註釋
Abstract: Current research has revealed visual perceptual deficits among Parkinson's disease (PD) subjects. Study 1 of the current dissertation examined the effects of a compressed visual hemi-field and/or a shifted egocentric reference point (ECRP) on the perception of optic flow and gait coordination in healthy age-matched control adults (n = 17), individuals whose PD initiated on the left-body side (LPD; n = 14) and individuals with right-sided motor symptoms (RPD; n = 9). Subjects wore a head mounted display (HMD) and walked a virtual hallway at 0.8 m/s. During symmetric conditions, optic flow speeds of both walls were randomly set to 0.0, 0.4, 0.8, 1.2 and 1.6 m/s. During asymmetric conditions, one wall, selected randomly, remained at 0.8 m/s, while the opposite wall was randomly manipulated through the above speeds. Kinematic data of upper and lower extremities were collected via an OptoTrak 3020 system. Walking speed, stride frequency, stride length, relative phase and frequency relations between limb pairs and lateral drift were calculated. Results indicate PD subjects experience an ECRP that has shifted toward the side of the initial basal ganglia damage; when walking, LPD veer to the right and RPD to the left. PD subjects produce smaller step lengths on the initially affected body side and use the opposite side to control gait. Study 2 investigated optic flow speed, spatial frequency, and temporal frequency manipulations on heading direction and various gait parameters among young healthy adults (n = 11). Data collection and analysis was similar to Study 1. The speed and spatial frequency of the right or left wall, selected at random, remained constant with 0.8 m/s and 45 dots/m. The opposite wall was manipulated through three optic flow speeds (i.e., 0.8, 1.2 and 1.8 m/s), spatial frequencies (i.e., 20, 30 and 45 dots/m) and temporal frequency combinations (i.e., 0.8 m/s with 45 dots/m, 1.2 m/s with 30 dots/m and 1.8 m/s with 20 dots/m). During optic flow speed and temporal frequency manipulations subjects veer away from the faster moving wall. When asymmetries in spatial frequency were presented, subjects walked toward the wall with lower spatial frequency, increasing the field of view on that side.