Reflex wind-up in early chronic spinal injury: Plasticity of motor outputs

Michael D. Johnson*, Alain Frigon, Marie France Hurteau, Charlette Cain, C. J. Heckman

*Corresponding author for this work

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

In this study we evaluate temporal summation (wind-up) of reflexes in select distal and proximal hindlimb muscles in response to repeated stimuli of the distal tibial or superficial peroneal nerves in cats 1 mo after complete spinal transection. This report is a continuation of our previous paper on reflex wind-up in the intact and acutely spinalized cat. To evaluate reflex wind-up in both studies, we recorded electromyographic signals from the following left hindlimb muscles: lateral gastrocnemius (LG), tibialis anterior (TA), semitendinosus (ST), and sartorius (Srt), in response to 10 electrical pulses to the tibial or superficial peroneal nerves. Two distinct components of the reflex responses were considered, a short-latency compound action potential (CAP) and a longer duration bout of sustained activity (SA). These two response types were shown to be differentially modified by acute spinal injury in our previous work (Frigon A, Johnson MD, Heckman CJ. J Physiol 590: 973-989, 2012). We show that these responses exhibit continued plasticity during the 1-mo recovery period following acute spinalization. During this early chronic phase, wind-up of SA responses returned to preinjury levels in one muscle, the ST, but remained depressed in all other muscles tested. In contrast, CAP response amplitudes, which were initially potentiated following acute transection, returned to preinjury levels in all muscles except for Srt, which continued to show marked increase. These findings illustrate that spinal elements exhibit considerable plasticity during the recovery process following spinal injury and highlight the importance of considering SA and CAP responses as distinct phenomena with unique underlying neural mechanisms. NEW & NOTEWORTHY This research is the first to assess temporal summation, also called wind-up, of muscle reflexes during the 1-mo recovery period following spinal injury. Our results show that two types of muscle reflex activity are differentially modulated 1 mo after spinal cord injury (SCI) and that spinal reflexes are altered in a muscle-specific manner during this critical period. This postinjury plasticity likely plays an important role in spasticity experienced by individuals with SCI.

Original languageEnglish (US)
Pages (from-to)2065-2074
Number of pages10
JournalJournal of neurophysiology
Volume117
Issue number5
DOIs
StatePublished - May 16 2017

Fingerprint

Spinal Injuries
Reflex
Muscles
Action Potentials
Peroneal Nerve
Hindlimb
Spinal Cord Injuries
Cats
Skeletal Muscle
Research

Keywords

  • Motoneuron
  • Reflex
  • Spinal cord injury
  • Wind-up

ASJC Scopus subject areas

  • Neuroscience(all)
  • Physiology

Cite this

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title = "Reflex wind-up in early chronic spinal injury: Plasticity of motor outputs",
abstract = "In this study we evaluate temporal summation (wind-up) of reflexes in select distal and proximal hindlimb muscles in response to repeated stimuli of the distal tibial or superficial peroneal nerves in cats 1 mo after complete spinal transection. This report is a continuation of our previous paper on reflex wind-up in the intact and acutely spinalized cat. To evaluate reflex wind-up in both studies, we recorded electromyographic signals from the following left hindlimb muscles: lateral gastrocnemius (LG), tibialis anterior (TA), semitendinosus (ST), and sartorius (Srt), in response to 10 electrical pulses to the tibial or superficial peroneal nerves. Two distinct components of the reflex responses were considered, a short-latency compound action potential (CAP) and a longer duration bout of sustained activity (SA). These two response types were shown to be differentially modified by acute spinal injury in our previous work (Frigon A, Johnson MD, Heckman CJ. J Physiol 590: 973-989, 2012). We show that these responses exhibit continued plasticity during the 1-mo recovery period following acute spinalization. During this early chronic phase, wind-up of SA responses returned to preinjury levels in one muscle, the ST, but remained depressed in all other muscles tested. In contrast, CAP response amplitudes, which were initially potentiated following acute transection, returned to preinjury levels in all muscles except for Srt, which continued to show marked increase. These findings illustrate that spinal elements exhibit considerable plasticity during the recovery process following spinal injury and highlight the importance of considering SA and CAP responses as distinct phenomena with unique underlying neural mechanisms. NEW & NOTEWORTHY This research is the first to assess temporal summation, also called wind-up, of muscle reflexes during the 1-mo recovery period following spinal injury. Our results show that two types of muscle reflex activity are differentially modulated 1 mo after spinal cord injury (SCI) and that spinal reflexes are altered in a muscle-specific manner during this critical period. This postinjury plasticity likely plays an important role in spasticity experienced by individuals with SCI.",
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Reflex wind-up in early chronic spinal injury : Plasticity of motor outputs. / Johnson, Michael D.; Frigon, Alain; Hurteau, Marie France; Cain, Charlette; Heckman, C. J.

In: Journal of neurophysiology, Vol. 117, No. 5, 16.05.2017, p. 2065-2074.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Reflex wind-up in early chronic spinal injury

T2 - Plasticity of motor outputs

AU - Johnson, Michael D.

AU - Frigon, Alain

AU - Hurteau, Marie France

AU - Cain, Charlette

AU - Heckman, C. J.

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N2 - In this study we evaluate temporal summation (wind-up) of reflexes in select distal and proximal hindlimb muscles in response to repeated stimuli of the distal tibial or superficial peroneal nerves in cats 1 mo after complete spinal transection. This report is a continuation of our previous paper on reflex wind-up in the intact and acutely spinalized cat. To evaluate reflex wind-up in both studies, we recorded electromyographic signals from the following left hindlimb muscles: lateral gastrocnemius (LG), tibialis anterior (TA), semitendinosus (ST), and sartorius (Srt), in response to 10 electrical pulses to the tibial or superficial peroneal nerves. Two distinct components of the reflex responses were considered, a short-latency compound action potential (CAP) and a longer duration bout of sustained activity (SA). These two response types were shown to be differentially modified by acute spinal injury in our previous work (Frigon A, Johnson MD, Heckman CJ. J Physiol 590: 973-989, 2012). We show that these responses exhibit continued plasticity during the 1-mo recovery period following acute spinalization. During this early chronic phase, wind-up of SA responses returned to preinjury levels in one muscle, the ST, but remained depressed in all other muscles tested. In contrast, CAP response amplitudes, which were initially potentiated following acute transection, returned to preinjury levels in all muscles except for Srt, which continued to show marked increase. These findings illustrate that spinal elements exhibit considerable plasticity during the recovery process following spinal injury and highlight the importance of considering SA and CAP responses as distinct phenomena with unique underlying neural mechanisms. NEW & NOTEWORTHY This research is the first to assess temporal summation, also called wind-up, of muscle reflexes during the 1-mo recovery period following spinal injury. Our results show that two types of muscle reflex activity are differentially modulated 1 mo after spinal cord injury (SCI) and that spinal reflexes are altered in a muscle-specific manner during this critical period. This postinjury plasticity likely plays an important role in spasticity experienced by individuals with SCI.

AB - In this study we evaluate temporal summation (wind-up) of reflexes in select distal and proximal hindlimb muscles in response to repeated stimuli of the distal tibial or superficial peroneal nerves in cats 1 mo after complete spinal transection. This report is a continuation of our previous paper on reflex wind-up in the intact and acutely spinalized cat. To evaluate reflex wind-up in both studies, we recorded electromyographic signals from the following left hindlimb muscles: lateral gastrocnemius (LG), tibialis anterior (TA), semitendinosus (ST), and sartorius (Srt), in response to 10 electrical pulses to the tibial or superficial peroneal nerves. Two distinct components of the reflex responses were considered, a short-latency compound action potential (CAP) and a longer duration bout of sustained activity (SA). These two response types were shown to be differentially modified by acute spinal injury in our previous work (Frigon A, Johnson MD, Heckman CJ. J Physiol 590: 973-989, 2012). We show that these responses exhibit continued plasticity during the 1-mo recovery period following acute spinalization. During this early chronic phase, wind-up of SA responses returned to preinjury levels in one muscle, the ST, but remained depressed in all other muscles tested. In contrast, CAP response amplitudes, which were initially potentiated following acute transection, returned to preinjury levels in all muscles except for Srt, which continued to show marked increase. These findings illustrate that spinal elements exhibit considerable plasticity during the recovery process following spinal injury and highlight the importance of considering SA and CAP responses as distinct phenomena with unique underlying neural mechanisms. NEW & NOTEWORTHY This research is the first to assess temporal summation, also called wind-up, of muscle reflexes during the 1-mo recovery period following spinal injury. Our results show that two types of muscle reflex activity are differentially modulated 1 mo after spinal cord injury (SCI) and that spinal reflexes are altered in a muscle-specific manner during this critical period. This postinjury plasticity likely plays an important role in spasticity experienced by individuals with SCI.

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