Abstract
Spinal cord injury (SCI) disrupts neuronal networks of ascending and descending tracts at the site of injury, leading to a loss of motor function. Restoration and new circuit formation are important components of the recovery process, which involves collateral sprouting of injured and uninjured fibers. The present study was conducted to determine cortical responses to antidromic stimulation of the corticospinal tracts, to compare changes in the reorganization of neural pathways within normal and spinal cord-injured rats, and to elucidate differences in spatiotemporal activity patterns of the natural progression and reorganization of neural pathways in normal and SCI animals using optical imaging. Optical signals were recorded from the motor cortex in response to electrical stimulation of the ventral horn of the L1 spinal cord. Motor evoked potentials (MEPs) were evaluated to demonstrate endogenous recovery of physiological functions after SCI. A significantly shorter N1 peak latency and broader activation in the MEP optical recordings were observed at 4 weeks after SCI, compared to 1 week after SCI. Spatiotemporal patterns in the cerebral cortex differed depending on functional recovery. In the present study, optical imaging was found to be useful in revealing functional changes and may reflect conditions of reorganization and/or changes in surviving neurons after SCI.
Highlights
Spinal cord injury (SCI) is a debilitating and devastating condition for most mammalian organisms
Representative spatiotemporal activity patterns were recorded from the motor cortex antidromically activated by 6-mA stimulation of the ventral horn at L1 spinal cord below the injury in the 1-W control and SCI rats (Figure 2A)
At 1 week after SCI, the distribution of the activation area was diminished, and optical responses were delayed in the Motor evoked potentials (MEPs) recording (Figure 2B)
Summary
Spinal cord injury (SCI) is a debilitating and devastating condition for most mammalian organisms. SCI causes disruption of networks of damaged axons and neural pathways, which is followed by restoration of plasticity and reorganization of neural networks in the spinal cord (Onifer et al, 2011). Neuroplasticity is the dynamic potential of the CNS to reorganize neural pathways and/or rehabilitate neuronal circuits (Nardone et al, 2013). Electrophysiology studies have shown evidence of network plasticity, Optical Imaging of Motor Cortex after SCI such as endogenous compensation and recovery mechanisms of the spinal cord and brain, after SCI (Nardone et al, 2013). Notwithstanding, the mechanisms of plastic restoration and neural reorganization in functional adaptation after SCI remained unclear
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