Motor learning in the "podokinetic" system and its role in spatial orientation during locomotion

• Published in: Experimental brain research Vol. 120; no. 3; pp. 377 - 385
• Main Authors: Weber, K. D., Fletcher, W. A., Gordon, C. R., Jones, G. Melvill, Block, E. W.
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01.06.1998
• Subjects: Adaptation, Physiological; Adult; Aged; Biological and medical sciences; Female; Fundamental and applied biological sciences. Psychology; Humans; Male; Middle Aged; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Orientation - physiology; Psychomotor Performance - physiology; Reference Values; Rotation; Spatial Behavior - physiology; Vertebrates: nervous system and sense organs; Walking - physiology; Human; Locomotion; Sensorimotor coordination; Vection; Spatial orientation; Sensorial perception; Vestibular system; Motor control; Adaptation; Foot
• ISSN: 0014-4819; 1432-1106
• DOI: 10.1007/s002210050411

The present study characterizes a previously reported adaptive phenomenon in a somatosensory-motor system involved in directional control of locomotor trajectory through foot contact with the floor. We call this the "podokinetic" (PK) system. Podokinetic adaptation was induced in six subjects by stepping in-place over the axis of a horizontally rotating disc over a range of disc angular velocities (11.25-90 degrees/s) and durations (7.5-60 min). After adaptation, subjects were blindfolded and attempted to step in-place on the floor without turning. Instead they all rotated relative to space. The rate of the "podokinetic afterrotation" (PKAR) was linearly related to stimulus amplitude up to 45 degrees/s, and the ratio of initial PKAR velocity to that of the adaptive stimulus was approximately 1:3. PKAR exhibited exponential decay, which was composed of "short-" and "long-term" components with "discharging" time constants on the order of 6-12 min and 1-2 h, respectively. The effect of stimulus duration on PKAR revealed a "charging" time constant that approximated that of the short-term component. A significant suppression of PKAR occurred during the 1 st min of the postadaptive response, suggesting functional interaction between the PK and vestibular systems during the period of vestibular stimulation. During PKAR subjects perceived no self-rotation, indicating that perception as well as locomotor control of spatial orientation were remodeled by adaptation of the PK system.