Time Course and Magnitude of Movement-Related Gating of Tactile Detection in Humans. III. Effect of Motor Tasks

• Published in: Journal of neurophysiology 2002-10, Vol.88 (4), p.1968-1979
• Main Authors: Williams, Stephan R, Chapman, C. Elaine
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Electric Stimulation; Electromyography; Female; Humans; Isometric Contraction - physiology; Isotonic Contraction - physiology; Male; Motor Activity - physiology; Movement - physiology; Touch - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.2002.88.4.1968

Centre de Recherche en Sciences Neurologiques,   1 Département de Physiologie, and   2 École de Réadaptation, Faculté de Médecine, Université de Montréal, Montreal, Quebec H3T 1J4, Canada Williams, Stephan R. and C. Elaine Chapman. Time Course and Magnitude of Movement-Related Gating of Tactile Detection in Humans. III. Effect of Motor Tasks. J. Neurophysiol. 88: 1968-1979, 2002. This study investigated the relative importance of central and peripheral signals for movement-related gating by comparing the time course and magnitude of movement-related decreases in tactile detection during a reference motor task, active isotonic digit 2 (D2) abduction, with that seen during three test tasks: a comparison with active isometric D2 abduction (movement vs. no movement) evaluated the contribution of peripheral reafference generated by the movement to gating; a comparison with passive D2 abduction (motor command vs. no motor command; movement generated by an external agent) allowed us to evaluate the contribution of the central motor command to tactile gating; and finally, the inclusion of an active "no apparatus," or freehand, D2 abduction task allowed us to evaluate the potential contribution of incidental peripheral reafference generated by the position detecting apparatus to the results (apparatus vs. no apparatus). Weak electrical stimuli (2-ms pulse; intensity, 90% detected at rest) were applied to D2 at different delays before and after movement onset or electromyographic (EMG) activity onset. Significant time-dependent movement-related decreases in detection were obtained with all tasks. When the results obtained during the active isotonic movement task were compared with those obtained in the three test tasks, no significant differences in the functions describing detection performance over time were seen. The results obtained with the isometric D2 abduction task show that actual movement of a body part is not necessary to diminish detection of tactile stimuli in a manner similar to the decrease produced by isotonic, active movement. In the passive test task, the peak decrease in detection clearly preceded the onset of passive movement (by 38 ms) despite the lack of a motor command and, presumably, no movement-related peripheral reafference. A slightly but not significantly earlier decrease was obtained with active movement (49 ms before movement onset). Expectation of movement likely did not contribute to the results because stimulus detection during sham