Ipsi- and Contralateral Oligo- and Polysynaptic Reflexes in Humans Revealed by Low-Frequency Epidural Electrical Stimulation of the Lumbar Spinal Cord
Epidural electrical stimulation (EES) applied over the human lumbosacral spinal cord provides access to afferent fibers from virtually all lower-extremity nerves. These afferents connect to spinal networks that play a pivotal role in the control of locomotion. Studying EES-evoked responses mediated...
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MDPI AG
2021-01-01
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| Series: | Brain Sciences |
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| Online Access: | https://www.mdpi.com/2076-3425/11/1/112 |
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| author | Ursula S. Hofstoetter Simon M. Danner Brigitta Freundl Heinrich Binder Peter Lackner Karen Minassian |
| author_facet | Ursula S. Hofstoetter Simon M. Danner Brigitta Freundl Heinrich Binder Peter Lackner Karen Minassian |
| author_sort | Ursula S. Hofstoetter |
| collection | DOAJ |
| description | Epidural electrical stimulation (EES) applied over the human lumbosacral spinal cord provides access to afferent fibers from virtually all lower-extremity nerves. These afferents connect to spinal networks that play a pivotal role in the control of locomotion. Studying EES-evoked responses mediated through these networks can identify some of their functional components. We here analyzed electromyographic (EMG) responses evoked by low-frequency (2–6 Hz) EES derived from eight individuals with chronic, motor complete spinal cord injury. We identified and separately analyzed three previously undescribed response types: first, crossed reflexes with onset latencies of ~55 ms evoked in the hamstrings; second, oligosynaptic reflexes within 50 ms post-stimulus superimposed on the monosynaptic posterior root-muscle reflexes in the flexor muscle tibialis anterior, but with higher thresholds and no rate-sensitive depression; third, polysynaptic responses with variable EMG shapes within 50–450 ms post-stimulus evoked in the tibialis anterior and triceps surae, some of which demonstrated consistent changes in latencies with graded EES. Our observations suggest the activation of commissural neurons, lumbar propriospinal interneurons, and components of the late flexion reflex circuits through group I and II proprioceptive afferent inputs. These potential neural underpinnings have all been related to spinal locomotion in experimental studies. |
| first_indexed | 2024-03-09T04:35:25Z |
| format | Article |
| id | doaj.art-f19099e25b7a40e0a50ad2bf3d3ce35a |
| institution | Directory Open Access Journal |
| issn | 2076-3425 |
| language | English |
| last_indexed | 2024-03-09T04:35:25Z |
| publishDate | 2021-01-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Brain Sciences |
| spelling | doaj.art-f19099e25b7a40e0a50ad2bf3d3ce35a2023-12-03T13:29:04ZengMDPI AGBrain Sciences2076-34252021-01-0111111210.3390/brainsci11010112Ipsi- and Contralateral Oligo- and Polysynaptic Reflexes in Humans Revealed by Low-Frequency Epidural Electrical Stimulation of the Lumbar Spinal CordUrsula S. Hofstoetter0Simon M. Danner1Brigitta Freundl2Heinrich Binder3Peter Lackner4Karen Minassian5Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, 1090 Vienna, AustriaDepartment of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, PA 19129, USANeurological Center, Klinik Penzing—Wiener Gesundheitsverbund, 1140 Vienna, AustriaNeurological Center, Klinik Penzing—Wiener Gesundheitsverbund, 1140 Vienna, AustriaNeurological Center, Klinik Penzing—Wiener Gesundheitsverbund, 1140 Vienna, AustriaCenter for Medical Physics and Biomedical Engineering, Medical University of Vienna, 1090 Vienna, AustriaEpidural electrical stimulation (EES) applied over the human lumbosacral spinal cord provides access to afferent fibers from virtually all lower-extremity nerves. These afferents connect to spinal networks that play a pivotal role in the control of locomotion. Studying EES-evoked responses mediated through these networks can identify some of their functional components. We here analyzed electromyographic (EMG) responses evoked by low-frequency (2–6 Hz) EES derived from eight individuals with chronic, motor complete spinal cord injury. We identified and separately analyzed three previously undescribed response types: first, crossed reflexes with onset latencies of ~55 ms evoked in the hamstrings; second, oligosynaptic reflexes within 50 ms post-stimulus superimposed on the monosynaptic posterior root-muscle reflexes in the flexor muscle tibialis anterior, but with higher thresholds and no rate-sensitive depression; third, polysynaptic responses with variable EMG shapes within 50–450 ms post-stimulus evoked in the tibialis anterior and triceps surae, some of which demonstrated consistent changes in latencies with graded EES. Our observations suggest the activation of commissural neurons, lumbar propriospinal interneurons, and components of the late flexion reflex circuits through group I and II proprioceptive afferent inputs. These potential neural underpinnings have all been related to spinal locomotion in experimental studies.https://www.mdpi.com/2076-3425/11/1/112commissural neuronscrossed reflexesepidural electrical stimulationhumanlocomotionmotor control |
| spellingShingle | Ursula S. Hofstoetter Simon M. Danner Brigitta Freundl Heinrich Binder Peter Lackner Karen Minassian Ipsi- and Contralateral Oligo- and Polysynaptic Reflexes in Humans Revealed by Low-Frequency Epidural Electrical Stimulation of the Lumbar Spinal Cord Brain Sciences commissural neurons crossed reflexes epidural electrical stimulation human locomotion motor control |
| title | Ipsi- and Contralateral Oligo- and Polysynaptic Reflexes in Humans Revealed by Low-Frequency Epidural Electrical Stimulation of the Lumbar Spinal Cord |
| title_full | Ipsi- and Contralateral Oligo- and Polysynaptic Reflexes in Humans Revealed by Low-Frequency Epidural Electrical Stimulation of the Lumbar Spinal Cord |
| title_fullStr | Ipsi- and Contralateral Oligo- and Polysynaptic Reflexes in Humans Revealed by Low-Frequency Epidural Electrical Stimulation of the Lumbar Spinal Cord |
| title_full_unstemmed | Ipsi- and Contralateral Oligo- and Polysynaptic Reflexes in Humans Revealed by Low-Frequency Epidural Electrical Stimulation of the Lumbar Spinal Cord |
| title_short | Ipsi- and Contralateral Oligo- and Polysynaptic Reflexes in Humans Revealed by Low-Frequency Epidural Electrical Stimulation of the Lumbar Spinal Cord |
| title_sort | ipsi and contralateral oligo and polysynaptic reflexes in humans revealed by low frequency epidural electrical stimulation of the lumbar spinal cord |
| topic | commissural neurons crossed reflexes epidural electrical stimulation human locomotion motor control |
| url | https://www.mdpi.com/2076-3425/11/1/112 |
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