Original Research ARTICLE
Fingertip-coupled spindle signaling does not contribute to reduce postural sway under light touch
- 1University of São Paulo, Brazil
- 2School of Arts, Sciences and Humanities, University of São Paulo, Brazil
The details of how light touch (LT) of a stable surface reduces postural sway are still not well known. We hypothesized that removal of feedback provided by muscle afferents of the touching fingertip would increase postural sway in standing subjects. Eleven participants stood upright on a force plate with eyes closed and on an unstable surface. The experimental conditions involved two different finger positions: PMA [with partial muscle afferents], which includes sensory information from the fingertip flexor muscles; and NMA [no muscle afferents], without information from either fingertip flexor or extensor muscles. In the control condition, the participants kept the same posture, but with no finger touch (NT). Postural sway in both anteroposterior (AP) and mediolateral (ML) axes were recorded. Results showed that LT decreased all sway quantifiers as compared with the NT condition. The withdrawal of information from the touch finger muscle afferents (NMA condition) did not increase postural sway. Actually, there was a small, albeit statistically significant, decrease in the variability of center of pressure displacement in the AP direction. These results indicate that in some cases muscle afferent input may either not contribute or even worsen the overall quality of sensory feedback from a given body segment, leading to no improvement or even a slightly decreased performance of the motor control system (evaluated by means of levels of postural sway in the present investigation). The results suggest that non-spindle fingertip afferents provide the bulk of the sensory feedback associated with the fingertip that is touching a ground-referenced object during quiet standing under LT.
Keywords: Postural control, Center of Pressure (COP), Muscle Spindles, fingertip touch, sensorimotor integration
Received: 18 Apr 2019;
Accepted: 05 Aug 2019.
Edited by:Taian M. Vieira, Polytechnic University of Turin, Italy
Reviewed by:Kei Masani, Toronto Rehabilitation Institute, University Health Network, Canada
KAZUSHIGE OSHITA, Kyushu Kyoritsu University, Japan
Copyright: © 2019 Silva, Magalhães and Kohn. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
PhD. Fernando H. Magalhães, University of São Paulo, São Paulo, 05508-010, São Paulo, Brazil, email@example.com
PhD. Andre F. Kohn, University of São Paulo, São Paulo, 05508-010, São Paulo, Brazil, firstname.lastname@example.org