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. 2017 Jan 1;117(1):36-46.
doi: 10.1152/jn.00169.2016. Epub 2016 Oct 12.

Sensorimotor Integration of Vision and Proprioception for Obstacle Crossing in Ambulatory Individuals With Spinal Cord Injury

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Free PMC article

Sensorimotor Integration of Vision and Proprioception for Obstacle Crossing in Ambulatory Individuals With Spinal Cord Injury

Raza Naseem Malik et al. J Neurophysiol. .
Free PMC article

Abstract

Skilled walking, such as obstacle crossing, is an essential component of functional mobility. Sensorimotor integration of visual and proprioceptive inputs is important for successful obstacle crossing. The objective of this study was to understand how proprioceptive deficits affect obstacle-crossing strategies when controlling for variations in motor deficits in ambulatory individuals with spinal cord injury (SCI). Fifteen ambulatory individuals with SCI and 15 able-bodied controls were asked to step over an obstacle scaled to their motor abilities under full and obstructed vision conditions. An eye tracker was used to determine gaze behaviour and motion capture analysis was used to determine toe kinematics relative to the obstacle. Combined, bilateral hip and knee proprioceptive sense (joint position sense and movement detection sense) was assessed using the Lokomat and customized software controls. Combined, bilateral hip and knee proprioceptive sense in subjects with SCI varied and was significantly different from able-bodied subjects. Subjects with greater proprioceptive deficits stepped higher over the obstacle with their lead and trail limbs in the obstructed vision condition compared with full vision. Subjects with SCI also glanced at the obstacle more frequently and with longer fixation times compared with controls, but this was not related to proprioceptive sense. This study indicates that ambulatory individuals with SCI rely more heavily on vision to cross obstacles and show impairments in key gait parameters required for successful obstacle crossing. Our data suggest that proprioceptive deficits need to be considered in rehabilitation programs aimed at improving functional mobility in ambulatory individuals with SCI.

New & noteworthy: This work is unique since it examines the contribution of combined, bilateral hip and knee proprioceptive sense on the recovery of skilled walking function, in addition to characterizing gaze behavior during a skilled walking task in people with motor-incomplete spinal cord injury.

Keywords: functional mobility; gaze behavior; obstacle crossing; proprioception; spinal cord injury.

Figures

Fig. 1.
Fig. 1.
Experimental setup. Participants walked between parallel bars and were asked to step over an obstacle positioned between a doorframe (indicating its spatial location) under full and obstructed vision conditions. Obstacle height for each subject was set at a level corresponding to average peak toe height during usual stepping plus 25% of the difference in peak toe height between maximum and usual stepping of the stronger limb [subjects with spinal cord inujry (SCI)] or dominant limb [ able-bodied (AB) subjects].
Fig. 2.
Fig. 2.
Gaze behavior. Total number of saccades (A) and total fixation time (B) in the second (Step-2) and (Step-1) step before crossing the obstacle are plotted for both able-bodied (white boxes) and spinal cord injured (black boxes) subjects.
Fig. 3.
Fig. 3.
Toe kinematics. Changes in lead (L) and trail (T) horizontal distance [ΔHORZ-L (A); ΔHORZ-T (B)] and vertical toe clearance [ΔVERT-L (C); ΔVERT-T (D)] between obstructed and full vision conditions are plotted for both able-bodied (white boxes) and spinal cord injured (black boxes) subjects. Horizontal line at 1 represents no change between conditions. Values greater than 1 represent a greater horizontal distance and higher toe clearance in the obstructed vision (OV) condition compared with the full vision (FV) condition. Values less than 1 represent a shorter horizontal distance and lower toe clearance in the OV condition compared with the FV condition.
Fig. 4.
Fig. 4.
Relationship between proprioceptive sense and the changes in vertical toe clearance between conditions. Changes in lead (L) and trail (T) vertical toe clearance (ΔVERT-L; A and B; ΔVERT-T, C and D) between obstructed and full vision conditions are plotted against overall joint position sense (A and C) and overall movement detection sense (B and D) for subjects with SCI.

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