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Journal article
Periodic modulation of repetitively elicited monosynaptic reflexes of the human lumbosacral spinal cord
Journal of neurophysiology, v 114(1), pp 400-410
01 Jul 2015
PMID: 25904708
Featured in Collection : UN Sustainable Development Goals @ Drexel
Abstract
In individuals with motor-complete spinal cord injury, epidural stimulation of the lumbosacral spinal cord at 2 Hz evokes unmodulated reflexes in the lower limbs, while stimulation at 22-60 Hz can generate rhythmic burstlike activity. Here we elaborated on an output pattern emerging at transitional stimulation frequencies with consecutively elicited reflexes alternating between large and small. We analyzed responses concomitantly elicited in thigh and leg muscle groups bilaterally by epidural stimulation in eight motor-complete spinal cord-injured individuals. Periodic amplitude modulation of at least 20 successive responses occurred in 31.4% of all available data sets with stimulation frequency set at 5-26 Hz, with highest prevalence at 16 Hz. It could be evoked in a single muscle group only but was more strongly expressed and consistent when occurring in pairs of antagonists or in the same muscle group bilaterally. Latencies and waveforms of the modulated reflexes corresponded to those of the unmodulated, monosynaptic responses to 2-Hz stimulation. We suggest that the cyclical changes of reflex excitability resulted from the interaction of facilitatory and inhibitory mechanisms emerging after specific delays and with distinct durations, including postactivation depression, recurrent inhibition and facilitation, as well as reafferent feedback activation. The emergence of large responses within the patterns at a rate of 5.5/s or 8/s may further suggest the entrainment of spinal mechanisms as involved in clonus. The study demonstrates that the human lumbosacral spinal cord can organize a simple form of rhythmicity through the repetitive activation of spinal reflex circuits.
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Details
- Title
- Periodic modulation of repetitively elicited monosynaptic reflexes of the human lumbosacral spinal cord
- Creators
- Ursula S. Hofstoetter - Medical University of ViennaSimon M. Danner - Medical University of ViennaBrigitta Freundl - Otto Wagner HospitalHeinrich Binder - Otto Wagner HospitalWinfried Mayr - Medical University of ViennaFrank Rattay - TU WienKaren Minassian - Medical University of Vienna
- Publication Details
- Journal of neurophysiology, v 114(1), pp 400-410
- Publisher
- Amer Physiological Soc
- Number of pages
- 11
- Grant note
- L512-N13 / Austrian Science Fund (FWF) LS11-057 / Vienna Science and Technology Fund (WWTF) WFL-AT-007/11 / Wings for Life Spinal Cord Research Foundation
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Neurobiology and Anatomy; College of Medicine; Drexel University
- Web of Science ID
- WOS:000358010600036
- Scopus ID
- 2-s2.0-84937677587
- Other Identifier
- 991020100061904721
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- Collaboration types
- Domestic collaboration
- Web of Science research areas
- Neurosciences
- Physiology