The Journal of Neurophysiology Vol. 87 No. 2 February 2002, pp. 1138-1141
Copyright ©2002 by the American Physiological Society

RAPID COMMUNICATION

Podokinetic After-Rotation Following Unilateral and Bilateral Podokinetic Stimulation

 ¹Department of Clinical Neurosciences and Neuroscience Research Group, The University of Calgary, Calgary, Alberta T2N 2T9, Canada; and  ²Balance Disorders Laboratory, Oregon Health and Science University, Beaverton, Oregon 97006

Earhart, Gammon M., G. Melvill Jones, F. B. Horak, E. W. Block, K. D. Weber, and W. A. Fletcher. Podokinetic After-Rotation Following Unilateral and Bilateral Podokinetic Stimulation. J. Neurophysiol. 87: 1138-1141, 2002. Previous studies demonstrated an aftereffect of walking on a rotating treadmill, involving inadvertent circular navigation with eyes closed [podokinetic after-rotation (PKAR)]. We compared PKAR following unilateral and bilateral podokinetic (PK) stimulation to determine whether the left and right legs could be independently adapted. Each subject performed two sessions of PK stimulation, stepping in place with one foot on either side of the axis of a rotating disk. Subjects experienced bilateral stimulation (i.e., both left and right feet stepped on the rotating disk) in one session and unilateral stimulation (i.e., the left foot stepped on the rotating disk and the right foot stepped on a stationary surface) in the other. Following stimulation, we recorded foot lift-off and touchdown times and pelvic angular velocity while subjects stepped in place on a stationary surface. PKAR velocity following unilateral stimulation was lower than that following bilateral stimulation. Following bilateral stimulation, pelvic rotation was in the counterclockwise (CCW) direction during single-limb support on both the left and right sides. Immediately following left unilateral stimulation, subjects demonstrated CCW pelvic rotation during left single-limb support but not during right single-limb support. Across the first 13 strides, the difference between left and right sides diminished; pelvic angular velocity was then CCW during single-limb support on both sides. This suggests that both the adapted left and the unadapted right limb influenced the final PKAR response with information from the two limbs being integrated over the first few strides.