Primary Sensory and Motor Cortex Excitability Are Co-Modulated in Response to Peripheral Electrical Nerve Stimulation

Abstract

Peripheral electrical stimulation (PES) is a common clinical technique known to induce changes in corticomotor excitability; PES applied to induce a tetanic motor contraction increases, and PES at sub-motor threshold (sensory) intensities decreases, corticomotor excitability. Understanding of the mechanisms underlying these opposite changes in corticomotor excitability remains elusive. Modulation of primary sensory cortex (S1) excitability could underlie altered corticomotor excitability with PES. Here we examined whether changes in primary sensory (S1) and motor (M1) cortex excitability follow the same time-course when PES is applied using identical stimulus parameters. Corticomotor excitability was measured using transcranial magnetic stimulation (TMS) and sensory cortex excitability using somatosensory evoked potentials (SEPs) before and after 30 min of PES to right abductor pollicis brevis (APB). Two PES paradigms were tested in separate sessions; PES sufficient to induce a tetanic motor contraction (30–50 Hz; strong motor intensity) and PES at sub motor-threshold intensity (100 Hz). PES applied to induce strong activation of APB increased the size of the N20-P25 component, thought to reflect sensory processing at cortical level, and increased corticomotor excitability. PES at sensory intensity decreased the size of the P25-N33 component and reduced corticomotor excitability. A positive correlation was observed between the changes in amplitude of the cortical SEP components and corticomotor excitability following sensory and motor PES. Sensory PES also increased the sub-cortical P14-N20 SEP component. These findings provide evidence that PES results in co-modulation of S1 and M1 excitability, possibly due to cortico-cortical projections between S1 and M1. This mechanism may underpin changes in corticomotor excitability in response to afferent input generated by PES.

Whole-hand water flow stimulation increases motor cortical excitability: a study of transcranial magnetic stimulation and movement-related cortical potentials

“…rMT is believed to reflect neuronal membrane excitability because it is increased by drugs that block voltagegated sodium channels (Ziemann et al 1996b) but not by drugs (Schabrun et al 2012;Thompson et al 2011), electrical skin stimulation (Golaszewski et al 2012;Golaszewski et al 2010), and muscle vibration Rosenkranz and Rothwell 2003) increases MEP recruitment curves. Some of these increases are considered due to increased excitability of spinal mechanisms (Claus et al 1988a;.…”

Presence and Absence of Muscle Contraction Elicited by Peripheral Nerve Electrical Stimulation Differentially Modulate Primary Motor Cortex Excitability

“…These MEP alterations have been proposed depending on the intensity (Chipchase et al, 2011a; Schabrun et al, 2012), frequency (Mang et al, 2010; Golaszewski et al, 2012), and duration (Andrews et al, 2013) of PES. Studies have also shown alterations in TMS-evoked MEPs following PES without concomitant changes in brainstem electrical stimulation-evoked MEPs (Kaelin-Lang et al, 2002) or electrical stimulation-evoked M- and F-waves, or H-reflex (Tinazzi et al, 2005; Mang et al, 2010; Golaszewski et al, 2012), suggesting that the observed modulation occurs at the cortical level.…”

“…One study compared MEPs following PES above and below the contraction threshold and reported that PES eliciting muscle contraction significantly increases MEP amplitude, while sub-MT PES significantly decreases MEP amplitude (Schabrun et al, 2012). However, it is unclear whether the changes in MEP amplitude are due to muscle contraction specifically or simply the electrical stimulation intensity, because Schabrun et al (2012) used different stimulation intensity between PES conditions (motor stimulation and sensory stimulations) for the same site (abductor pollicis brevis, APB). Therefore, the details of the alterations in excitability in the M1 after PES with and without muscle contraction are unknown.…”

Neuromuscular electrical stimulation of the median nerve facilitates low motor cortex excitability in patients with spinocerebellar ataxia

“…The cerebellum would then send out the feedback to upper motor neurons in the cerebral cortex via the cerebellothalamocortical tract, which responds to contralateral cortical inhibition (Argyelan et al, 2009;Molnar et al, 2004;Ni et al, 2010). A recent study found that peripheral electrical stimulation could co-modulate the excitability of primary sensory and motor cortexes in healthy humans (Schabrun et al, 2012). This study supports the claim that peripheral electrical stimulation is relayed to the primary sensory cortex via thalamo-cortical projections, activating or inducing a change in sensory processing, and this provides the signal for long term potentiation or depression-like changes in the primary motor cortex.…”

“…NMES possesses the feature of easy control of the amplitude of evoked muscle contraction and the sequential induction of movement. Recent studies have reported that NMES could co-modulate the excitability of both primary motor and sensory cortexes in healthy humans (Schabrun et al, 2012). The temporary neuroplasticity induced by NMES for functional reorganization has been observed to occur via motor afferents (Chang et al, 2011).…”