Repeated cathodal transspinal pulse and direct current stimulation modulate cortical and corticospinal excitability differently in healthy humans

Murray, Lynda M.; Knikou, Maria

doi:10.1007/s00221-019-05559-2

Cited by 19 publications

(22 citation statements)

References 61 publications

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“…For the first time reported in the literature, this clinical trial focused on coupling locomotor training with paired stimulation of the nervous system taking advantage of Hebbian mechanisms of neuroplasticity ( 33 , 48 , 49 ). PAS was timed to occur during the stance phase because transspinal stimulation produces bilateral leg extension at rest and during standing in people with and without SCI ( 37 , 50 , 51 ). In the transspinal-TMS PAS and locomotor training protocol, the transspinal stimulation induced ascending afferent volleys reached primary motor cortex at time that allowed to affect the descending motor volleys at their site of origin ( 26 ).…”

Section: Discussionmentioning

confidence: 99%

“…Transspinal stimulation was delivered based on procedures we have previously used on people with and without SCI ( 36 , 37 ). A single cathode electrode (Uni-Patch TM , 10.2 x 5.1 cm 2 , Wabasha, MA, USA) was placed at the T10 spinous process, identified via palpation and anatomical landmarks, equally between the left and right paravertebrae sides, and secured with Tegaderm transparent film (3M Healthcare, St. Paul, MN, USA).…”

Section: Methodsmentioning

confidence: 99%

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Neurophysiological Changes After Paired Brain and Spinal Cord Stimulation Coupled With Locomotor Training in Human Spinal Cord Injury

et al. 2021

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Neurophysiological changes that involve activity-dependent neuroplasticity mechanisms via repeated stimulation and locomotor training are not commonly employed in research even though combination of interventions is a common clinical practice. In this randomized clinical trial, we established neurophysiological changes when transcranial magnetic stimulation (TMS) of the motor cortex was paired with transcutaneous thoracolumbar spinal (transspinal) stimulation in human spinal cord injury (SCI) delivered during locomotor training. We hypothesized that TMS delivered before transspinal (TMS-transspinal) stimulation promotes functional reorganization of spinal networks during stepping. In this protocol, TMS-induced corticospinal volleys arrive at the spinal cord at a sufficient time to interact with transspinal stimulation induced depolarization of alpha motoneurons over multiple spinal segments. We further hypothesized that TMS delivered after transspinal (transspinal-TMS) stimulation induces less pronounced effects. In this protocol, transspinal stimulation is delivered at time that allows transspinal stimulation induced action potentials to arrive at the motor cortex and affect descending motor volleys at the site of their origin. Fourteen individuals with motor incomplete and complete SCI participated in at least 25 sessions. Both stimulation protocols were delivered during the stance phase of the less impaired leg. Each training session consisted of 240 paired stimuli delivered over 10-min blocks. In transspinal-TMS, the left soleus H-reflex increased during the stance-phase and the right soleus H-reflex decreased at mid-swing. In TMS-transspinal no significant changes were found. When soleus H-reflexes were grouped based on the TMS-targeted limb, transspinal-TMS and locomotor training promoted H-reflex depression at swing phase, while TMS-transspinal and locomotor training resulted in facilitation of the soleus H-reflex at stance phase of the step cycle. Furthermore, both transspinal-TMS and TMS-transspinal paired-associative stimulation (PAS) and locomotor training promoted a more physiological modulation of motor activity and thus depolarization of motoneurons during assisted stepping. Our findings support that targeted non-invasive stimulation of corticospinal and spinal neuronal pathways coupled with locomotor training produce neurophysiological changes beneficial to stepping in humans with varying deficits of sensorimotor function after SCI.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Neurophysiological Changes After Paired Brain and Spinal Cord Stimulation Coupled With Locomotor Training in Human Spinal Cord Injury

et al. 2021

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“…H-reflex transmission is carried by Ia afferents that synapse with segmental spinal motor neurons. These synapses are susceptible to homosynaptic and post-activation depression, i.e., when H-reflex stimuli are delivered in intervals of roughly five seconds or less, responses are blunted after the first response [9,10,45]. Multiple groups have shown that at most intensities, especially subthreshold intensity, TSCS also activates largediameter dorsal afferent fibers, and are alternatively termed posterior root reflexes [44].…”

Section: Discussionmentioning

confidence: 99%

Posteroanterior Cervical Transcutaneous Spinal Cord Stimulation: Interactions with Cortical and Peripheral Nerve Stimulation

Wecht

Savage

Famodimu

et al. 2021

JCM

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Transcutaneous spinal cord stimulation (TSCS) has demonstrated potential to beneficially modulate spinal cord motor and autonomic circuitry. We are interested in pairing cervical TSCS with other forms of nervous system stimulation to enhance synaptic plasticity in circuits serving hand function. We use a novel configuration for cervical TSCS in which the anode is placed anteriorly over ~C4–C5 and the cathode posteriorly over ~T2–T4. We measured the effects of single pulses of TSCS paired with single pulses of motor cortex or median nerve stimulation timed to arrive at the cervical spinal cord at varying intervals. In 13 participants with and 15 participants without chronic cervical spinal cord injury, we observed that subthreshold TSCS facilitates hand muscle responses to motor cortex stimulation, with a tendency toward greater facilitation when TSCS is timed to arrive at cervical synapses simultaneously or up to 10 milliseconds after cortical stimulus arrival. Single pulses of subthreshold TSCS had no effect on the amplitudes of median H-reflex responses or F-wave responses. These findings support a model in which TSCS paired with appropriately timed cortical stimulation has the potential to facilitate convergent transmission between descending motor circuits, segmental afferents, and spinal motor neurons serving the hand. Studies with larger numbers of participants and repetitively paired cortical and spinal stimulation are needed.

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“…Against expectations, tsDCS did not alter the intracortical excitability of the primary somatosensory cortex assessed by paired stimulation of TN SEPs. Even though there is evidence of tsDCS influencing cortical circuits and functional connectivity offside its site of application 15,16,[32][33][34]44 , there is no data available yet on its effect on the intracortical excitability of the primary somatosensory cortex. By evaluating the suppressive effect of a precursory stimulus on a subsequent stimulus of an evoked cortical potential, PSS is a commonly used tool to estimate intracortical excitability 35,36,[45][46][47] and seems to reflect inhibitory cortical processes 36,48 .…”

Section: Discussionmentioning

confidence: 99%

“…TsDCS affects descending pathways [20][21][22] and spinal reflexes of different levels [23][24][25][26][27] resulting in first therapeutic approaches in patients with restless legs syndrome 28 , hereditary spastic paraplegia 29 or spinal cord injuries 24,30,31 . Additionally, tsDCS significantly alters amplitudes of motor evoked potentials after paired-pulse transcranial magnetic stimulation 32 , decreases intracortical inhibition and increases intracortical facilitation 33 underlining the impact of tsDCS on motor cortex excitability and descending pathways.…”

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confidence: 95%

Transcutaneous spinal direct current stimulation shows no effect on paired stimulation suppression of the somatosensory cortex

Bettmann

Meyer-Frießem

Schweizer

et al. 2020

Sci Rep

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Transcutaneous spinal direct current stimulation (tsDCS) is a safe and convenient method of neuromodulation. It has been proven to alter sensory processing at cervicomedullary level by amplitude changes of the P30 response of tibial nerve somatosensory evoked potentials (TN SEPs). With knowledge that tsDCS affects cortical circuits, we hypothesized that tsDCS may also affect intracortical excitability of the somatosensory cortex assessed by paired stimulation suppression (PSS). Fourteen healthy men were included in this prospective, single-blinded, placebo-controlled crossover study. Single (SS) and paired stimulation (PS) TN SEPs were recorded over the scalp before, immediately as well as 30 and 60 min after applying 15 min of tsDCS over the twelfth thoracic vertebra. Each volunteer underwent three independent and randomized sessions of either cathodal, anodal or sham stimulation. tsDCS showed no effect on peak-to-peak amplitudes or latencies of cortical P40-N50 response after SS. Furthermore, tsDCS failed to induce significant changes on amplitude ratios of PSS, thus showing no impact on intracortical excitability of the somatosensory cortex in healthy subjects. Further research is required to reveal the different mechanisms and to strengthen clinical use of this promising technique.

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Repeated cathodal transspinal pulse and direct current stimulation modulate cortical and corticospinal excitability differently in healthy humans

Cited by 19 publications

References 61 publications

Neurophysiological Changes After Paired Brain and Spinal Cord Stimulation Coupled With Locomotor Training in Human Spinal Cord Injury

Neurophysiological Changes After Paired Brain and Spinal Cord Stimulation Coupled With Locomotor Training in Human Spinal Cord Injury

Posteroanterior Cervical Transcutaneous Spinal Cord Stimulation: Interactions with Cortical and Peripheral Nerve Stimulation

Transcutaneous spinal direct current stimulation shows no effect on paired stimulation suppression of the somatosensory cortex

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