Podokinetic after-rotation in Parkinson disease

Abstract

Walking on a rotating platform for 15 min causes healthy subjects to involuntarily turn when walking without vision. This adaptive response, called podokinetic after-rotation (PKAR), uses the same kinematic patterns as voluntary turning suggesting that PKAR and voluntary turning share common mechanisms. The purpose of this study is to determine whether people with Parkinson disease (PD), a condition that produces substantial disability from turning difficulties, can adapt to the rotating platform. Initial testing of people with PD revealed that most were unable to step on the rotating platform for 15 continuous minutes. We thus tested a less intense version of the paradigm in eight healthy people. On one day, subjects walked on the platform for 15 continuous minutes; on another day, they walked on the platform for three 5-minute intervals separated by 5-minute rests. After both sessions, subjects rested for 5 min then walked in place for 30 min without vision, while we recorded rotational velocity of PKAR. Continuous and interval protocols effectively elicited robust PKAR. We then tested eight subjects with PD and matched controls using the 5-minute interval protocol and recorded PKAR responses for 10 min. There were no significant differences between the PD and control groups. We conclude that PD subjects can adapt to the rotating platform and develop PKAR from interval training. Future studies are needed to determine whether the rotating platform may act as a rehabilitative tool to reinforce motor patterns for turning and alleviate turning difficulties in people with PD.

Figure 1

A. Illustration of individual plots of a young control subject’s trunk angular velocities during 30 minutes of PKAR after long continuous PK stimulation (filled circles) versus PK stimulation in short intervals (open triangles). Note the similarities between the two plots. B. Illustration of group plots of mean trunk angular velocities during 30 minutes of PKAR after long continuous PK stimulation (filled circles) versus PK stimulation is short intervals (open triangles). Standard deviation (SD) is marked at every minute. Note the overlap of the curves for the two conditions. Both protocols elicited robust PKAR responses.

Figure 2

A. Illustration of individual plots of trunk angular velocities from a subject with PD (black triangles) and a matched control subject (gray triangles) during 10 minutes of PKAR after PK stimulation in short intervals. Note the similarities of the two curves. B. Illustration of group plots of mean trunk angular velocities during 10 minutes of PKAR in PD (black triangles) versus control (gray triangles) groups after PK stimulation in short intervals. SD is marked at every minute. The shape of the curves are very similar and there is substantial overlap of the error bars. Both groups showed robust PKAR responses.

Figure 3

A. Illustration of individual plots of trunk angular velocities during 10 minutes of PKAR in a young (open triangles) and an old (gray triangles) control subjects after PK stimulation in intervals. Note the similarities of the two curves. B. Illustration of group plots of mean trunk angular velocities during 10 minutes of PKAR in young (open triangles) versus old (gray triangles) controls after PK stimulation in short intervals. SD is marked at every minute. There is substantial amount of overlap in the two curves. PKAR does not appear to be age-dependent.

Figure 4

Example of experiment setup. Twelve reflective markers were placed on each participant; three on the head (center of forehead, occipital protuberance and top of head), three on the trunk (left acromion, right acromion and left scapula) and three on each foot (heel, 2^nd metatarsal and lateral malleolus). The subjects stepped in the middle of the rotating platform counteracting the circular motion of the platform. They held a low-friction wheel overhead and subjects in study 2 wore a modified parachute harness for added safety.