Spasms after spinal cord injury show low-frequency intermuscular coherence

Abstract

Intermuscular coherence allows the investigation of common input to muscle groups. Although beta-band (15–30 Hz) intermuscular coherence is well understood as originating from the cortex, the source of intermuscular coherence at lower frequencies is still unclear. We used a wearable device that recorded electromyographic (EMG) signals during a 24-h period in four lower limb muscles of seven spinal cord injury patients (American Spinal Cord Injury Association impairment scale: A, 6 subjects; B, 1 subject) while they went about their normal daily life activities. We detected natural spasms occurring during these long-lasting recordings and calculated intermuscular coherence between all six possible combinations of muscle pairs. There was significant intermuscular coherence at low frequencies, between 2 and 13 Hz. The most likely source for this was the spinal cord and its peripheral feedback loops, because the spinal lesions in these patients had interrupted connections to supraspinal structures. This is the first report to demonstrate that the spinal cord is capable of producing low-frequency intermuscular coherence with severely reduced or abolished descending drive.NEW & NOTEWORTHY This is the first report to demonstrate that intermuscular coherence between lower limb muscles at low frequencies can be produced by the spinal cord with severely reduced or abolished descending drive.

Older adults show elevated intermuscular coherence in eyes‐open standing but only young adults increase coherence in response to closing the eyes

“…Aguiar et al. (2018) observed significant intermuscular coherence in lower‐limb muscle pairs over 2–13 Hz in spinal cord injury patients, suggesting that coherence in these frequencies can be generated by spinal circuits. This interpretation would agree with the notion that ∼10 Hz coherence could be generated at the spinal level by Ia afferent activity (Lippold 1970).…”

“…Intermuscular coherence within the 15–30 Hz frequency band has been shown to reflect common cortical input to spinal α‐motoneurons (Baker, Olivier, & Lemon, 1997; Baker, Pinches, & Lemon, 2003; Farmer et al., 1993) and it seems to have a strong supraspinal component since stroke and spinal cord injury reduces or ablates coherence (Aguiar et al., 2018; Farmer et al., 1993; Norton et al. 2006) during isometric contraction.…”

“…Coherence measured from two muscle pairs may reflect cortical, subcortical and/or spinal influences (Grosse, Cassidy, & Brown, 2002). Coherence in the 0–6 Hz band is thought to be related to force production/fluctuations (Bourguignon et al., 2017), while in the 8–14 Hz band coherence could reflect proprioceptive feedback from Ia afferents (Lippold 1970), and coherence in the 15–30 Hz band seems to have a strong supraspinal component (Aguiar, Baker, Gant, Bohorquez, & Thomas, 2018; Farmer, Swash, Ingram, & Stephens, 1993; Norton, Wood, Marsden, & Day, 2003). The interest in the 15–30 Hz band in human movement studies investigating the corticospinal tract seems justified since stroke and spinal cord injury reduce or ablate coherence during isometric contraction (Aguiar et al., 2018; Farmer et al., 1993; Norton et al.…”

Acute spinal cord injury: Pathophysiology and pharmacological intervention (Review)

“…Studies reveal that blocking the NMDA receptor results in protection from secondary damage due to trauma and ischemia in animal models ( 39 , 40 ). NMDA antagonists can significantly improve neurological functions and decrease the incidence of edema ( 41 , 42 ). Magnesium ions can block the ion channels of the NMDA receptors ( 14 ).…”

Properties of the surface electromyogram following traumatic spinal cord injury: a scoping review

“…sEMG allows us to assess in high resolution the activity of several muscles at the same time during complex motor tasks, including activities of daily living, gait or reaching to grasping movements. It further allows the exploration of neuromuscular properties at rest or under passive movements, the residual control of volitional activity by the motor cortex, and the spontaneous or reflex activity intrinsic to the spinal cord [ 13 ]. Given the variety and depth of information that can be obtained from sEMG, an accurate interpretation of the signal properties after SCI is needed.…”