Vestibular-somatosensory convergence in head movement control during locomotion after long-duration space flight¹

Issue title: 8th Symposium on the Role of the Vestibular Organs in Space Exploration April 8–10, 2011, Houston, TX, USA

Guest editors: Charles M. Oman

Article type: Research Article

Authors: Mulavara, A.P.^{a; *} | Ruttley, T.^b | Cohen, H.S.^c | Peters, B.T.^d | Miller, C.^d | Brady, R.^d | Merkle, L.^d | Bloomberg, J.J.^b

Affiliations: [a] Universities Space Research Association, Houston, TX, USA | [b] NASA Johnson Space Center, Houston, TX, USA | [c] Baylor College of Medicine, Houston, TX, USA | [d] Wyle Integrated Science and Engineering Group, Houston, TX, USA | Man Vehicle Laboratory, Massachusetts Institute of Technology, Cambridge, MA, USA

Correspondence: [*] Address for correspondence: Ajitkumar P. Mulavara, PhD, 2101 NASA parkway, MC-SK/B272, Universities Space Research Association, Houston, TX, USA. E-mail: ajitkumar.p.mulavara@nasa.gov

Note: [1] This paper was presented at the Session: Adaptation and Rehabilitation at the 8th Symposium on the Role of the Vestibular Organs in Space Exploration, April 8–10, 2011, Houston, TX, USA

Abstract: Space flight causes astronauts to be exposed to adaptation in both the vestibular and body load-sensing somatosensory systems. The goal of these studies was to examine the contributions of vestibular and body load-sensing somatosensory influences on vestibular mediated head movement control during locomotion after long-duration space flight. Subjects walked on a motor driven treadmill while performing a gaze stabilization task. Data were collected from three independent subject groups that included bilateral labyrinthine deficient (LD) patients, normal subjects before and after 30 minutes of 40% bodyweight unloaded treadmill walking, and astronauts before and after long-duration space flight. Motion data from the head and trunk segments were used to calculate the amplitude of angular head pitch and trunk vertical translation movement while subjects performed a gaze stabilization task, to estimate the contributions of vestibular reflexive mechanisms in head pitch movements. Exposure to unloaded locomotion caused a significant increase in head pitch movements in normal subjects, whereas the head pitch movements of LD patients were significantly decreased. This is the first evidence of adaptation of vestibular mediated head movement responses to unloaded treadmill walking. Astronaut subjects showed a heterogeneous response of both increases and decreases in the amplitude of head pitch movement. We infer that body load-sensing somatosensory input centrally modulates vestibular input and can adaptively modify vestibularly mediated head-movement control during locomotion. Thus, space flight may cause central adaptation of the converging vestibular and body load-sensing somatosensory systems leading to alterations in head movement control.

Keywords: Space flight, vestibular, somatosensory, convergence, head movement control, locomotion

DOI: 10.3233/VES-2011-0435

Journal: Journal of Vestibular Research, vol. 22, no. 2-3, pp. 153-166, 2012