Mechanical flutter stimulation induces a lasting response in the sensorimotor cortex as revealed with BOLD fMRI

Abstract

It has been recently shown that 20 min of mechanical flutter stimulation induces lasting motor cortical excitability changes, as assessed by transcranial magnetic stimulation in relaxed hand muscles. The present functional magnetic resonance imaging (fMRI) study aims to examine if such neuromodulatory changes are reflected in the BOLD signal during a motor test. Therefore, two groups were recruited: one group receiving whole-hand flutter stimulation with a frequency of 25 Hz (FSTIM group, n = 22) and a second group receiving no stimulation (NOSTIM group, n = 22). As motor test finger-to-thumb tapping was performed to activate a wide sensorimotor network during the fMRI measurements. Three fMRI measurements were obtained with this test: before stimulation (PRE), after stimulation (POST1), and 1 h after stimulation (POST2). Three regions of interest (ROIs) were defined: primary motor area (M1), primary somatosensory area (S1), and supplementary motor area. In the absence of baseline differences between both groups, the FSTIM group showed increased movement-related brain activations compared with the NOSTIM group, both at POST1 and POST2. ROI analysis revealed increased blood-oxygenation-level-dependent (BOLD) responses within contralateral S1 (+20%) and M1 (+25%) at POST1, which lasted until POST2. These poststimulatory effects within S1 and M1 obviously reflect neuroplastic changes associated with augmented cortical excitability. These findings are of high clinical relevance, for example, to improve the treatment of stroke patients.

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

“…None of the studies investigating changes in the BOLD signal strength could find differences in the activation of S2 (Christova et al, 2012;Golaszewski et al, 2004;Wu et al, 2005), which is in contrast to the findings on localization of activation peaks and activated clusters (Hodzic et al, 2004;Pleger et al, 2003). It was proposed that the lack of effect in studies treating BOLD signal changes relates to the fact that S2 is less somatotopically organized and that there is more overlap between representations of different body sites.…”

“…RTS increased activity in M1 as well as S1 was found through fMRI (Christova et al, 2012;Wu et al, 2005) and MEG (Golaszewski et al, 2010;Golaszewski et al, 2012;Kowalewski et al, 2012). Indeed, Wu et al found an even bigger increase of activation in M1 than in S1 (Wu, van Gelderen et al 2005).…”

“…Studies investigating the reversibility of effects after a shorter time window found an even earlier recovery of fMRI signal changes within the range of 2 hours after whole hand burst stimulation (Golaszewski et al, 2004). The duration of fMRI signal changes induced by mechanical stimulation of the finger and palm were shorter lasting and recovered within 1 hour (Christova et al, 2012). Also median nerve stimulation induced changes for only 1 hour (Wu et al, 2005).…”

“…Yet, in these studies it is difficult to estimate in how far the increase in voxel number reflected increased cortical representation or just a stronger blood-oxygen-level dependent (BOLD) signal. BOLD signal strength has been shown to increase by about 20 % after TENS as well as after 20 minutes of mechanical 25 Hz stimulation (Christova et al, 2012;Wu et al, 2005). A single pulse protocol reported a 100 % increase in signal strength .…”

“…Dinse et al, 2006;Höffken et al, 2007;Kalisch et al, 2007;Kalisch et al, 2008;Pilz, Veit, Braun, & Godde, 2004), or rather stimulation of the whole hand simultaneously with a specific glove to maximize the effect of coactivation (Christova et al, 2011;Golaszewski et al, 1999;Golaszewski et al, 2004;Golaszewski et al, 2010;Golaszewski et al, 2012). Few studies also stimulated other body parts, such as the palm or foot (Christova, Rafolt, Mayr, Wilfling, & Gallasch, 2010;Christova et al, 2012;Peurala et al, 2002).…”