Effects of Transcranial Stimulation With Direct and Alternating Current on Resting-State Functional Connectivity: An Exploratory Study Simultaneously Combining Stimulation and Multiband Functional Magnetic Resonance Imaging.

Marine Mondino,Sukhmanjit Ghumman,Kevin Whittingstall,Emmanuelle Renauld,Shirley Fecteau,Claire Gane

doi:10.3389/fnhum.2019.00474

Abstract

Background: Transcranial stimulation with direct (tDCS) and alternating current (tACS) has increasingly gained interest in various fields, from cognitive neuroscience to clinical investigations. Transcranial current stimulation used alone may modulate brain activity that consequently influences behaviors, without providing information on potentially induced brain activity changes. The combination of transcranial current stimulation and functional magnetic resonance imaging (fMRI) may help to address this. This exploratory study investigated instantaneous and subsequent effects of tDCS and tACS on resting-state functional connectivity (rsFC) in healthy adults.Methods: We conducted a randomized crossover study with 15 healthy subjects receiving three stimulation conditions (tDCS, tACS, and sham) on separate days. Stimulation was applied over the left and right dorsolateral prefrontal cortex (DLPFC) for 30 min (1 mA). rsFC of the targeted prefrontal areas was assessed before, during, and after stimulation using multiband fMRI and using left and right DLPFC as seeds.Results: Both tDCS and tACS increased rsFC during and after the stimulation period, as compared to sham. tDCS-induced changes were observed between the left DLPFC and bilateral parietal regions at the junction of the superior parietal and the inferior parietal lobules. tACS-induced changes were observed between the left DLPFC and the right inferior parietal lobule.Conclusion: Overall, these results suggest that a single session with a low dose, 1 mA, of tDCS or tACS can cause changes in fronto-parietal connectivity that occur rapidly, that is, within the first 15 min. Although exploratory, this work contributes to the discussion of the potential of transcranial current stimulation to modulate resting-state networks and the interest of combining transcranial current stimulation with neuroimaging to identify these changes.

Highlights

Noninvasive transcranial stimulation techniques such as transcranial direct current stimulation and transcranial alternating current stimulation are increasingly used in clinical and cognitive science
One brain region that is often targeted with transcranial stimulation (tCS) in clinical and cognitive studies is the dorsolateral prefrontal cortex (DLPFC). tCS applied over the DLPFC has been shown to modulate symptoms in various psychiatric disorders such as depression (Brunoni et al, 2017; Alexander et al, 2019) and cognitive functions such as memory, attention (Dedoncker et al, 2016; Hill et al, 2016), and higher-order cognitive processes such as multitasking performances (Hsu et al, 2015, 2017, 2019)
Most studies characterizing tCS-induced brain connectivity changes targeted the primary motor cortex or only one DLPFC. They found that tCS can induce resting-state functional connectivity changes locally under the electrodes as well as distal from the electrodes. Those targeting one DLPFC reported that transcranial direct current stimulation (tDCS) modulated rsFC within the fronto-parietal network (Keeser et al, 2011; Peña-Gómez et al, 2012), a resting-state network involved in cognitive engagement and attention, and mix findings in regard to the default mode network (DMN; Keeser et al, 2011; Peña-Gómez et al, 2012), which is thought to reflect an intrinsic state associated with self-related processes (Buckner et al, 2008)

Summary

Introduction

Noninvasive transcranial stimulation (tCS) techniques such as transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS) are increasingly used in clinical and cognitive science. Most studies characterizing tCS-induced brain connectivity changes targeted the primary motor cortex or only one DLPFC (e.g., anode over F3 and cathode over the right supraorbital area; for a review, see Wörsching et al, 2016). Overall, they found that tCS can induce resting-state functional connectivity (rsFC) changes locally under the electrodes as well as distal from the electrodes. The combination of transcranial current stimulation and functional magnetic resonance imaging (fMRI) may help to address this This exploratory study investigated instantaneous and subsequent effects of tDCS and tACS on restingstate functional connectivity (rsFC) in healthy adults

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Discussion

Conclusion