title: Effects and after-effects of voluntary intermittent light finger touch on body sway.
abstract: Effects of light touch on body sway have usually been investigated with some form of constant contact. Only two studies investigated transient sway dynamics following the addition or withdrawal of light touch. This study adopted a paradigm of intermittent touch and assessed body sway during as well as following short periods of touch of varying durations to investigate whether effects and after-effects of touch differ as a function of touch duration. In a modified heel-to-toe posture, 15 blindfolded participants alternated their index finger position between no-touching and touching on a strain gauge in response to low- and high-pitched auditory cues. Five trials of 46 s duration were segmented into 11 sections: a 6-s no-touching period was followed by five pseudo-randomly ordered touching periods of 0.5-, 1-, 1.5-, 2-, and 5-s duration, each of which was followed by another 6-s no-touching interval. Consistent with previous research, compared to no-touching intervals sway was reduced during touch periods with touch durations greater than 2 s. Progressive reductions in sway were evident after touch onset. After touch withdrawal in the 2-s touch condition, postural sway increased and returned to baseline level nearly immediately. Interestingly, in the 5-s touch condition, reductions in sway persisted even after touch withdrawal in the medio-lateral and antero-posterior plane for around 2.5 s and 5.5 s, respectively. Our intermittent touch paradigm resulted in duration-dependent touch effects and after-effects; the latter is a novel finding and may result from a more persistent postural set involved in proactive sway control.
authors.affiliation: Department of Sport and Health Sciences, Technical University Munich, Munich, Germany; Behavioural Brain Sciences Centre, School of Psychology, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Leif
authors.initials: L
authors.lastname: Johannsen
authors.affiliation: School of Occupational Therapy, Chung Shan Medical University, Taichung, Taiwan.
authors.forename: Shu-Zon
authors.initials: SZ
authors.lastname: Lou
authors.affiliation: Physical Therapy Room, Chung Shan Medical University Hospital, Taichung, Taiwan; School of Physical Therapy, Chung Shan Medical University, Taichung, Taiwan. Electronic address: hychen@csmu.edu.tw.
authors.forename: Hui-Ya
authors.initials: HY
authors.lastname: Chen
mesh_terms: D003463:Cues; D005260:Female; D005385:Fingers; D006801:Humans; D008297:Male; D004856:Postural Balance / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors; D014110:Touch; D055815:Young Adult
keywords: After-effects; Intermittent; Light touch; Postural sway; Standing balance