Modulation of Resting State Functional Connectivity of the Motor Network by Transcranial Pulsed Current Stimulation

Abstract

The effects of transcranial pulsed current stimulation (tPCS) on resting state functional connectivity (rs-FC) within the motor network were investigated. Eleven healthy participants received one magnetic resonance imaging (MRI) session with three resting state functional MRI (rs-fMRI) scans, one before stimulation (PRE-STIM) to collect baseline measures, one during stimulation (STIM), and one after 13 min of stimulation (POST-STIM). Rs-FC measures during the STIM and POST-STIM conditions were compared to the PRE-STIM baseline. Regions of interest for the rs-FC analysis were extracted from the significantly activated clusters obtained during a finger tapping motor paradigm and included the right primary motor cortex (R M1), left primary motor cortex (L M1), supplemental motor area (SMA), and cerebellum (Cer). The main findings were reduced rs-FC between the left M1 and surrounding motor cortex, and increased rs-FC between the left M1 and left thalamus during stimulation, but increased rs-FC between the Cer and right insula after stimulations. Bivariate measures of connectivity demonstrate reduced strength of connectivity for the whole network average (p=0.044) and reduced diversity of connectivity for the network average during stimulation (p=0.024). During the POST-STIM condition, the trend of reduced diversity for the network average was statistically weaker (p=0.071). In conclusion, while many of the findings are comparable to previous reports using simultaneous transcranial direct current stimulation (tDCS) and fMRI acquisition, we also demonstrate additional changes in connectivity patterns that are induced by tPCS.

Changes in resting state functional connectivity after repetitive transcranial direct current stimulation applied to motor cortex in fibromyalgia patients

“…Our findings are somewhat at odds with the existing literature. For example, researchers in some studies have reported increases in thalamic blood flow [ 32 ] or increased M1–thalamus connectivity after M1 stimulation [ 17 , 33 ]. We suggest that these conflicting results can be explained by the timing of stimulation and measurement.…”

Primary somatosensory cortex and periaqueductal gray functional connectivity as a marker of the dysfunction of the descending pain modulatory system in fibromyalgia

“…ROIs were acquired from prior studies as seeds. Together, they were used to create rs-FC maps of specific networks related to chronic pain and FM for each subject, with rs-FC being measured using the following source seeds (see Table 1 for coordinates): PAG [ 6 ], left (L) and right (R) primary and secondary somatosensory cortex (L_S1, R_S1, L_S2, R_S2) [ 25 ], left and right primary motor cortex (L_M1, R_M1) [ 26 ], left and right dorsolateral and ventromedial prefrontal cortexes (L_DLPFC, R_DPLFC, L_MPFC, R_MPFC) [ 27 , 28 ], left and right anterior and posterior insular cortexes (L_aIC, L_pIC, R_aIC, R_pIC), left and right ACC (L_ACC, R_ACC) [ 25 ], left and right ventrolateral and mediodorsal thalamus (L_VLTh, R_VLTh, L_MDTh, R_MDTh) [ 29 , 30 ], left and right hippocampus (L_Hippo, R_Hippo) [ 31 ], amygdalae (L_Amyg, R_Amyg) [ 32 ], and nucleus accumbens (L_NA, R_NA) [ 33 ]. After calculating the subjects’ FC map, the second-level comparison was performed through an ROI-to-ROI analysis.…”

Transcranial pulsed current stimulation: A scoping review of the current literature on scope, nature, underlying mechanisms, and gaps

“…The relevant fMRI studies found altered rs-FC between M1 and surrounding neural networks during a-tPCS at 15 Hz. This inter-regional correlation of signal intensities has suggested the capability of the stimulation to modulate brain regions that are functionally connected (Alon et al, 2011;Sours et al, 2014). However, a report of a-tPCs at 75 Hz on M1 has shown that they are less related to the functional connectivity behind the stimulatory effects.…”