Repetitive tactile stimulation changes resting-state functional connectivity—implications for treatment of sensorimotor decline

Abstract

Neurological disorders and physiological aging can lead to a decline of perceptual abilities. In contrast to the conventional therapeutic approach that comprises intensive training and practicing, passive repetitive sensory stimulation (RSS) has recently gained increasing attention as an alternative to countervail the sensory decline by improving perceptual abilities without the need of active participation. A particularly effective type of high-frequency RSS, utilizing Hebbian learning principles, improves perceptual acuity as well as sensorimotor functions and has been successfully applied to treat chronic stroke patients and elderly subjects. High-frequency RSS has been shown to induce plastic changes of somatosensory cortex such as representational map reorganization, but its impact on the brain's ongoing network activity and resting-state functional connectivity has not been investigated so far. Here, we applied high-frequency RSS in healthy human subjects and analyzed resting state Electroencephalography (EEG) functional connectivity patterns before and after RSS by means of imaginary coherency (ImCoh), a frequency-specific connectivity measure which is known to reduce over-estimation biases due to volume conduction and common reference. Thirty minutes of passive high-frequency RSS lead to significant ImCoh-changes of the resting state mu-rhythm in the individual upper alpha frequency band within distributed sensory and motor cortical areas. These stimulation induced distributed functional connectivity changes likely underlie the previously observed improvement in sensorimotor integration.

Sex-Specific Links in Motor and Sensory Adaptations to Repetitive Motion–Induced Fatigue

“…In addition, fatigue-terminal AD thresholds were significantly greater in the condition with sensory stimulation than when stimulation was absent (Time × Condition interaction). Despite previous research demonstrating that sensory supplementation has a beneficial effect on sensory function (Freyer, Reinacher, Nolte, Dinse, & Ritter, 2012;Kalisch, Tegenthoff, & Dinse, 2008), our data suggest that stimulation may add the effects of fatigue on the sensory system and lead to a larger decrease in sensory detection capability. Results from other experimental fatigue protocols have found significant increases in sensory thresholds of both fatigued and nonfatigued muscles (Han et al, 2015;Kosek & Lundberg, 2003;Moufflet & Côté, 2015).…”

Computational models and motor learning paradigms: Could they provide insights for neuroplasticity after stroke? An overview

“…Few studies have demonstrated improvement of limb function (as scored by validated outcome measures) in patients treated to reduce excitability in contralesional M1, both in the sub-acute and in the chronic phase after stroke [48].The ability to recover motor functions after stroke is strongly influenced by the integrity of high-speed fibres connecting M1 to the spinal cord [14]. Since brain plasticity is virtually maintained regardless of age, changes in environmental conditions may impact the reorganisation of the cerebral cortex [49]. These findings indicate that there is potential for functional plasticity in the cerebral cortex of adults and suggest that rehabilitation programmes may influence this process.…”

Tactile stimulation interventions: Influence of stimulation parameters on sensorimotor behavior and neurophysiological correlates in healthy and clinical samples

“…In addition to topographical changes, rTS influences connectivity of the sensory cortex, through interactions of sensory, motor and association cortices (Freyer et al, 2012). Evidence for this stems from EEG resting state measurements, which supported an increased connectivity of these areas after stimulation (Freyer et al, 2012).In order to estimate the connectivity, EEG coherence was measured during the resting state. This measure measures in how far the neuronal dynamics in different regions correlate.…”

“…Here, burst stimuli, with inter-burst intervals of about 5 seconds were used (Freyer, Reinacher, Nolte, Dinse, & Ritter, 2012;Freyer, Becker, Dinse, & Ritter, 2013;Kalisch et al, 2007;Tossi, Stude, Schwenkreis, Tegenthoff, & Dinse, 2013).…”

“…As with regard to mislocalization, as well as 2PD, prolonging stimulation from 2 to more hours could not improve tactile performance any further in either burst or single pulse stimulation (Freyer et al, 2012;Freyer et al, 2013;Godde et al, 2000;Ragert et al, 2008).…”