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Dissertation
Lumbar spinal interneuron activity as it relates to rhythmic motor output in the adult, spinal, air-stepping cat
Doctor of Philosophy (Ph.D.), Drexel University
30 May 2014
DOI:
https://doi.org/10.17918/etd-6043
Abstract
Interneurons of the lumbar spinal cord inherently maintain and modulate stepping. In order to advance therapeutic interventions for spinal cord injury, it is necessary to clearly understand both the localized locomotor spinal circuitry as well as the activation patterns within the spinal cord. In this study, the structural organization of interneurons regulating antagonistic motor pools and the neural activation patterns driving behavior were investigated. In-vivo extracellularly recorded neurons of the intermediate zone and ventral horn of the lumbar spinal cord were concurrently measured with hindlimb EMGs in the adult, air-stepping, spinal cat. Our results demonstrate that spinal interneurons participate in one of two ensembles which are highly correlated to opposing muscle bursts during stepping. Furthermore, the interneurons' firing phases were independent of their rostrocaudal locations. These findings suggest that spinal interneurons act within networks tuned to opposing phases of stepping which are heterogeneously mixed throughout the lumbar enlargement. Spectral power of extracellularly recorded continuous multiunit signals was found to be greater in mid-lumbar segments L3-L5 during stepping, supportive of previous lesioning studies isolating lumbar rhythmic generating centers to these segments in the cat. There was also greater multiunit power during the flexion phase of stepping than the extension phase of stepping in all lumbar segments. Finally, the multiunit power showed no phase lag at coherent frequencies throughout the lumbar enlargement indicative of a longitudinal standing wave of neural activation. Together, these results support that the spinal multiunit activity behaves as a synchronously active distributed network of caudally decreasing rhythmogenic potential, with greater power during the flexion phase of stepping. Furthermore, the results are unique in that it verifies and extends previous findings from the isolated, neonatal spinal cord to the in-vivo, mature and behaving system.
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Details
- Title
- Lumbar spinal interneuron activity as it relates to rhythmic motor output in the adult, spinal, air-stepping cat
- Creators
- Chantal Marie McMahon - DU
- Contributors
- Michel A. Lemay (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- School of Biomedical Engineering, Science, and Health Systems (1997-2026); Drexel University
- Other Identifier
- 6043; 991014632730104721