title: Modulating Arm Swing Symmetry with Cognitive Load: A Window on Rhythmic Spinal Locomotor Networks in Humans?
abstract: In healthy subjects, changes in arm swing symmetry while walking are observed when a cognitive dual task is added, with a tendency toward left-dominant arm swing as cognitive load increases. We applied a modified Stroop word/color naming paradigm to investigate this effect in spinal cord injured (SCI) patients. Six patients with cervical SCI (cSCI), 6 with thoracic injuries (tSCI; all 12 patients American Spinal Injury Association [ASIA] Injury Score [AIS]D), and 12 healthy, matched controls underwent three-dimensional 3D gait analysis while walking normally at a comfortable speed (NW) and when performing an additional congruent (CS) and incongruent (IS) Stroop task. An arm swing symmetry index (ASI)-in which positive values indicate proportionally more movement on the left and vice versa-was calculated. Even in the baseline NW condition, all three subject groups showed larger arm movements on the left. In controls, ASI increased (NW, 13.7 ± 6.3; CS, 16.6 ± 6.4; IS, 19.6 ± 7.8) as the task became more demanding. A larger shift in tSCI patients (NW, 15.8 ± 6.0; CS, 23.4 ± 3.8; IS, 30.7 ± 4.4) was driven by a significant reduction in right wrist trajectory (p = 0.014), whereas cSCI patients showed a small reduction in mean ASI with high variability (NW, 14.2 ± 10.7; CS, 9.3 ± 13.5; IS, 6.0 ± 12.9). The effect of the IS task on ASI compared to baseline (NW) was significantly different between tSCI (+12.5 ± 6.3) and cSCI (-8.2 ± 6.0) patients (p = 0.011). Disruption of the long propriospinal connections coordinating arm and leg movements during walking may explain the heightened sensitivity to manipulation of cognitive load in tSCI, whereas the more robust automaticity in cSCI may be attributed to impaired supraspinal inputs in the context of preserved intraspinal pathways.
authors: 1 Spinal Cord Injury Center, University Hospital Balgrist , Zurich, Switzerland .
authors: Tim
authors: T
authors: Killeen
authors: 1 Spinal Cord Injury Center, University Hospital Balgrist , Zurich, Switzerland .
authors: Christopher S
authors: CS
authors: Easthope
authors: 2 Department of Neurology, University Hospital Zurich , Zurich, Switzerland .
authors: Linard
authors: L
authors: Filli
authors: 2 Department of Neurology, University Hospital Zurich , Zurich, Switzerland .|3 Department of Neurology, Helios-Klinik Hagen-Ambrock , Hagen, Germany .
authors: Michael
authors: M
authors: Linnebank
authors: 1 Spinal Cord Injury Center, University Hospital Balgrist , Zurich, Switzerland .
authors: Armin
authors: A
authors: Curt
authors: 1 Spinal Cord Injury Center, University Hospital Balgrist , Zurich, Switzerland .
authors: Marc
authors: M
authors: Bolliger
authors: 1 Spinal Cord Injury Center, University Hospital Balgrist , Zurich, Switzerland .
authors: Björn
authors: B
authors: Zörner
mesh_terms: D000328:Adult; D000368:Aged; D001132:Arm / Q000502:physiology*; D001696:Biomechanical Phenomena / Q000502:physiology; D003071:Cognition / Q000502:physiology*; D005080:Exercise Test / Q000379:methods; D005260:Female; D006801:Humans; D008124:Locomotion / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology*; D013119:Spinal Cord Injuries / Q000503:physiopathology* / Q000534:rehabilitation; D016138:Walking / Q000502:physiology / Q000523:psychology
keywords: arm swing; dual-task; motor control; spinal cord injury; symmetry