TY - JOUR
T1 - Spasticity may obscure motor learning ability after stroke
AU - Subramanian, Sandeep K.
AU - Feldman, Anatol G.
AU - Levin, Mindy F.
N1 - Funding Information:
The project was supported by Collaborative Health Research Program Grant CHRP-337296-2007 (joint initiative between the Natural Sciences and Engineering Research Council of Canada and the Canadian Institutes of Health Research; to A. G. Feldman and M. F. Levin. M. F. Levin holds a Canada Research Chair in Motor Recovery and Rehabilitation. S. K. Subramanian was supported by a postdoctoral award from the Heart and Stroke Foundation of Canada and the Elaine Belanger and Ester Cushing Fellowship, McGill University.
Publisher Copyright:
© 2018 American Physiological Society. All rights reserved.
PY - 2018/1
Y1 - 2018/1
N2 - Previous motor learning studies based on adapting movements of the hemiparetic arm in stroke subjects have not accounted for spasticity occurring in specific joint ranges (spasticity zones), resulting in equivocal conclusions about learning capacity. We compared the ability of participants with stroke to rapidly adapt elbow extension movements to changing external load conditions outside and inside spasticity zones. Participants with stroke (n = 12, aged 57.8 ± 9.6 yr) and healthy age-matched controls (n = 8, 63.5 ± 9.1 yr) made rapid 40°–50° horizontal elbow extension movements from an initial (3°) to a final (6°) target. Sixteen blocks (6–10 trials/block) consisting of alternating loaded (30% maximal voluntary contraction) and non-loaded trials were made in one (controls) or two sessions (stroke; 1 wk apart). For the stroke group, the tonic stretch reflex threshold angle at which elbow flexors began to be activated during passive elbow extension was used to identify the beginning of the spasticity zone. The task was repeated in joint ranges that did or did not include the spasticity zone. Error correction strategies were identified by the angular positions before correction and compared between groups and sessions. Changes in load condition from no load to load and vice versa resulted in undershoot and overshoot errors, respectively. Stroke subjects corrected errors in 1–4 trials compared with 1–2 trials in controls. When movements did not include the spasticity zone, there was an immediate decrease in the number of trials needed to restore accuracy, suggesting that the capacity to learn may be preserved after stroke but masked by the presence of spasticity. NEW & NOTEWORTHY When arm movements were made outside, instead of inside, the range affected by spasticity, there was an immediate decrease in the number of trials needed to restore accuracy in response to a change in the external load. This suggests that motor learning processes may be preserved in patients with stroke but masked by the presence of spasticity in specific joint ranges. This has important implications for designing rehabilitation interventions predicated on motor learning principles.
AB - Previous motor learning studies based on adapting movements of the hemiparetic arm in stroke subjects have not accounted for spasticity occurring in specific joint ranges (spasticity zones), resulting in equivocal conclusions about learning capacity. We compared the ability of participants with stroke to rapidly adapt elbow extension movements to changing external load conditions outside and inside spasticity zones. Participants with stroke (n = 12, aged 57.8 ± 9.6 yr) and healthy age-matched controls (n = 8, 63.5 ± 9.1 yr) made rapid 40°–50° horizontal elbow extension movements from an initial (3°) to a final (6°) target. Sixteen blocks (6–10 trials/block) consisting of alternating loaded (30% maximal voluntary contraction) and non-loaded trials were made in one (controls) or two sessions (stroke; 1 wk apart). For the stroke group, the tonic stretch reflex threshold angle at which elbow flexors began to be activated during passive elbow extension was used to identify the beginning of the spasticity zone. The task was repeated in joint ranges that did or did not include the spasticity zone. Error correction strategies were identified by the angular positions before correction and compared between groups and sessions. Changes in load condition from no load to load and vice versa resulted in undershoot and overshoot errors, respectively. Stroke subjects corrected errors in 1–4 trials compared with 1–2 trials in controls. When movements did not include the spasticity zone, there was an immediate decrease in the number of trials needed to restore accuracy, suggesting that the capacity to learn may be preserved after stroke but masked by the presence of spasticity. NEW & NOTEWORTHY When arm movements were made outside, instead of inside, the range affected by spasticity, there was an immediate decrease in the number of trials needed to restore accuracy in response to a change in the external load. This suggests that motor learning processes may be preserved in patients with stroke but masked by the presence of spasticity in specific joint ranges. This has important implications for designing rehabilitation interventions predicated on motor learning principles.
KW - Goal-directed behavior
KW - Motor control
KW - Motor learning
KW - Spasticity
KW - Stroke rehabilitation
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U2 - 10.1152/jn.00362.2017
DO - 10.1152/jn.00362.2017
M3 - Article
C2 - 28904099
AN - SCOPUS:85043486316
VL - 119
SP - 5
EP - 20
JO - Journal of Neurophysiology
JF - Journal of Neurophysiology
SN - 0022-3077
IS - 1
ER -