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Grau JW, Baine RE, Bean PA, Davis JA, Fauss GN, Henwood MK, Hudson KE, Johnston DT, Tarbet MM, Strain MM. Learning to promote recovery after spinal cord injury. Exp Neurol 2020; 330:113334. [PMID: 32353465 PMCID: PMC7282951 DOI: 10.1016/j.expneurol.2020.113334] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 04/19/2020] [Accepted: 04/26/2020] [Indexed: 02/06/2023]
Abstract
The present review explores the concept of learning within the context of neurorehabilitation after spinal cord injury (SCI). The aim of physical therapy and neurorehabilitation is to bring about a lasting change in function-to encourage learning. Traditionally, it was assumed that the adult spinal cord is hardwired-immutable and incapable of learning. Research has shown that neurons within the lower (lumbosacral) spinal cord can support learning after communication with the brain has been disrupted by means of a thoracic transection. Noxious stimulation can sensitize nociceptive circuits within the spinal cord, engaging signal pathways analogous to those implicated in brain-dependent learning and memory. After a spinal contusion injury, pain input can fuel hemorrhage, increase the area of tissue loss (secondary injury), and undermine long-term recovery. Neurons within the spinal cord are sensitive to environmental relations. This learning has a metaplastic effect that counters neural over-excitation and promotes adaptive learning through an up-regulation of brain-derived neurotrophic factor (BDNF). Exposure to rhythmic stimulation, treadmill training, and cycling also enhances the expression of BDNF and counters the development of nociceptive sensitization. SCI appears to enable plastic potential within the spinal cord by down-regulating the Cl- co-transporter KCC2, which reduces GABAergic inhibition. This enables learning, but also fuels over-excitation and nociceptive sensitization. Pairing epidural stimulation with activation of motor pathways also promotes recovery after SCI. Stimulating motoneurons in response to activity within the motor cortex, or a targeted muscle, has a similar effect. It is suggested that a neurofunctionalist approach can foster the discovery of processes that impact spinal function and how they may be harnessed to foster recovery after SCI.
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Affiliation(s)
- James W Grau
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA.
| | - Rachel E Baine
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
| | - Paris A Bean
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
| | - Jacob A Davis
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
| | - Gizelle N Fauss
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
| | - Melissa K Henwood
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
| | - Kelsey E Hudson
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
| | - David T Johnston
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
| | - Megan M Tarbet
- Behavioral and Cellular Neuroscience, Department of Psychology, Texas A&M University, College Station, TX 77843, USA
| | - Misty M Strain
- Battlefield Pain Research, U.S. Army Institute of Surgical Research, 3698 Chambers Pass, BHT-1, BSA Fort Sam Houston, TX 78234, USA
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Brumley MR, Strain MM, Devine N, Bozeman AL. The Spinal Cord, Not to Be Forgotten: the Final Common Path for Development, Training and Recovery of Motor Function. Perspect Behav Sci 2018; 41:369-393. [PMID: 31976401 DOI: 10.1007/s40614-018-00177-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Research on learning, memory, and neural plasticity has long focused on the brain. However, the spinal cord also exhibits these phenomena to a remarkable degree. Following a spinal cord injury, the isolated spinal cord in vivo can adapt to the environment and benefit from training. The amount of plasticity or recovery of function following a spinal injury often depends on the age at which the injury occurs. In this overview, we discuss learning in the spinal cord, including associative conditioning, neural mechanisms, development, and applications to clinical populations. We take an integrated approach to the spinal cord, one that combines basic and experimental information about experience-dependent learning in animal models to clinical treatment of spinal cord injuries in humans. From such an approach, an important goal is to better inform therapeutic treatments for individuals with spinal cord injuries, as well as develop a more accurate and complete account of spinal cord and behavioral functioning.
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Affiliation(s)
- Michele R Brumley
- 1Department of Psychology, Idaho State University, 921 South 8th Avenue, Stop 8112, Pocatello, ID 83209-8112 USA
| | - Misty M Strain
- 2United States Army Institute of Surgical Research, JBSA-Fort Sam Houston, San Antonio, TX USA
| | - Nancy Devine
- 3Department of Physical and Occupational Therapy, Idaho State University, Pocatello, ID USA
| | - Aimee L Bozeman
- 1Department of Psychology, Idaho State University, 921 South 8th Avenue, Stop 8112, Pocatello, ID 83209-8112 USA
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