PT  - JOURNAL ARTICLE
AU  - Naveed Ejaz
AU  - Jing Xu
AU  - Meret Branscheidt
AU  - Benjamin Hertler
AU  - Heidi Schambra
AU  - Mario Widmer
AU  - Andreia V. Faria
AU  - Michelle Harran
AU  - Juan C. Cortes
AU  - Nathan Kim
AU  - Tomoko Kitago
AU  - Pablo A. Celnik
AU  - Andreas Luft
AU  - John W. Krakauer
AU  - Jörn Diedrichsen
TI  - Finger recruitment patterns during mirror movements suggest two systems for hand recovery after stroke
AID  - 10.1101/129510
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 129510
4099  - http://biorxiv.org/content/early/2017/04/22/129510.short
4100  - http://biorxiv.org/content/early/2017/04/22/129510.full
AB  - Accumulating behavioural and neurophysiological evidence suggests that upper-limb control relies on contributions from both cortical and subcortical motor circuits, with cortical inputs providing fine-finger function and subcortical inputs providing the ability for gross movements, respectively. During recovery of function after stroke, the relative contributions from these pathways may shift. Here we propose that mirror movements that appear after stroke provide a non-invasive assay through which relative contributions from cortical and subcortical pathways towards hand recovery can be studied. We hypothesized that mirror movements, like hand function, are generated by summed contributions from cortical and subcortical pathways, and suggest that subcortical contributions should be characterized by a broad recruitment of fingers, while cortical contributions primarily recruit the homologous finger in the passive hand. In a longitudinal stroke recovery study (Xu et al., 2016), we quantified mirror movements and paretic hand function in 53 stroke patients in the year following unilateral stroke. Mirror movements in the non-paretic hand were exaggerated early after damage (week 2), with paretic finger presses broadly recruiting multiple fingers in the non-paretic hand. On average, however, mirroring in homologous fingers was 1.76 times larger than in non-homologous fingers. Over the year, mirroring in the non-paretic hand progressively normalized with a time-course that mimicked that for the fine-finger deficits in the paretic hand. In comparison, during non-paretic finger presses, the homologous component of mirroring in the paretic hand was reduced early after stroke (week 2) but progressively normalized. Altogether, we conclude that the pattern of mirror movements across homologous and non-homologous fingers reflect the summed contributions of both cortical and subcortical systems, and we discuss the implications of our results towards hand recovery after stroke.