Motoneurone afterhyperpolarisation time-course following stroke |
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| Institution: | 1. Department of Physical Therapy, University of British Columbia, Vancouver, British Columbia, Canada;2. Graduate Program in Health and Rehabilitation Sciences, University of Western Ontario, London, Ontario, Canada;3. Spinal Cord Research Centre, Department of Physiology, University of Manitoba, Winnipeg, Manitoba, Canada;1. Groupement de Recherche Clinique et Technologique sur le Handicap (EA 4497), CIC-IT 805, Université de Versailles Saint Quentin, Garches, France;2. Laboratory of Human Motricity, Sport, Education and Health (EA 6309), University of Nice Sophia Antipolis, France;1. Institut für Physikalische Chemie, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany;2. Institut für Computerphysik, Universität Stuttgart, D-70569 Stuttgart, Germany;3. Institut für Theoretische Physik, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany |
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| Abstract: | ObjectiveOur aim was to investigate any changes in the estimated time-course of the afterhyperpolarisation (AHP) in motoneurones innervating the tibialis anterior following stroke, with a secondary objective to compare the results from two different AHP estimation techniques.MethodsMotor units from tibialis anterior on the paretic and non-paretic sides of 15 subjects with chronic stroke were recorded using intramuscular electrodes during voluntary isometric contraction. Participants varied the motor unit firing rate from its lowest rate to approximately 10 Hz. The AHP duration was estimated using the interval death rate (IDR) and transition point methods.ResultsThe AHP decay time-constant was significantly different between sides (paretic: 41.7 ± 8.5 ms, non-paretic: 36.2 ± 6.4 ms). Additionally, the paretic AHP time-constant was significantly longer in participants with low motor recovery (45.9 ± 9.1 ms) than with high motor recovery (39.3 ± 10.0 ms) as measured by CMSA score. The AHP estimates from the two techniques were correlated (r = 0.78).ConclusionsThe AHP time-course prolongation on the paretic side of people with chronic stroke is more pronounced in people with low motor recovery.SignificanceChanges in the motoneurone AHP time course post-stroke were related to muscle function and may play a role in the commonly-observed reduction of motor unit discharge rate during voluntary contractions following stroke. |
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| Keywords: | Afterhyperpolarisation Human Stroke |
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