Transcranial direct current stimulation and power spectral parameters: a tDCS/EEG co-registration study

Abstract

Transcranial direct current stimulation (tDCS) delivers low electric currents to the brain through the scalp. Constant electric currents induce shifts in neuronal membrane excitability, resulting in secondary changes in cortical activity. Concomitant electroencephalography (EEG) monitoring during tDCS can provide valuable information on the tDCS mechanisms of action. This study examined the effects of anodal tDCS on spontaneous cortical activity in a resting brain to disclose possible modulation of spontaneous oscillatory brain activity. EEG activity was measured in ten healthy subjects during and after a session of anodal stimulation of the postero-parietal cortex to detect the tDCS-induced alterations. Changes in the theta, alpha, beta, and gamma power bands were investigated. Three main findings emerged: (1) an increase in theta band activity during the first minutes of stimulation; (2) an increase in alpha and beta power during and after stimulation; (3) a widespread activation in several brain regions.

Assessing cortical synchronization during transcranial direct current stimulation: A graph-theoretical analysis

“…Because these two local measures are related to the shortest paths related to the examined node, possibly there are no reasons because such measures should change when the network is not required to increase its performance to solve a task. These results have some points in common with previous online tDCS-EEG studies (Mangia et al, 2014;Roy et al, 2014), as well as with offline tDCS-EEG studies (Polania et al, 2011a(Polania et al, , 2011bPellicciari et al, 2013).…”

“…It is well established that tDCS alters the cortical neuronal firing rate, in a polarity-specific manner, specifically in terms of increased activity after anodal stimulation (Bindman et al, 1964;Purpura and McMurtry, 1965). Such an increase was actually coupled with decreased connectivity in the slow rhythms (i.e., theta), which could be related to local and global cortical excitability alterations (Mangia et al, 2014;Ulam et al, 2014). Although it is well established that theta rhythms increase during active movement and that theta-enhanced transmission across brain regions may be important for several different functions, such as facilitating the transfer of information from one brain region to another during different types of information processing (for a review, see Colgin, 2013), the role of theta frequency in the resting state condition is not clear.…”

“…Because electrical stimulation affects large areas of the brain cortex, tDCS-induced cortical modification should result in a complex combination of both local and global excitation/inhibition phenomena (Borchers et al, 2012). To try to explain these alterations and to gain new insight into these mechanisms, tDCS and electroencephalographic (EEG) recordings have been used in sequential offline (Miniussi et al, 2012), and online tDCS-EEG approaches (e.g., Accornero et al, 2014;Baxter et al, 2014;Mangia et al, 2014), or in combination with other techniques (Hunter et al, NeuroImage xxx (2016) 2013), such as transcranial magnetic stimulation (TMS) (Pellicciari et al, 2013;Romero et al, 2014), magnetoencephalography (e.g., Garcia-Cossio et al, 2015) and electromyography (EMG) (Dutta et al, 2014). Until now, studies using EEG have shown how the tDCS induces polarity-specific on brain activity oscillations in different frequency bands (Kirov et al, 2009;Miller et al, 2015;Notturno et al, 2014;Song et al, 2014;Spitoni et al, 2013;Ulam et al, 2014).…”

Effect of Anodal-tDCS on Event-Related Potentials: A Controlled Study

“…This presents a complex picture of the effect of tDCS in general, as it may be specific to brain areas and functions. This appears to be consistent with a number of studies that when taken together exhibit varied findings on the effects of A-tDCS on EEG measurable cortical activity [38–40]. …”

Surface EEG-Transcranial Direct Current Stimulation (tDCS) Closed-Loop System

“…12–15 Also, EEG power is a reliable measure to detect specific cognitive and motor features across sessions, 16,17 as well as the effects of tDCS. 18,19 Invasive closed-loop systems incorporating EEG and brain stimulation techniques have been demonstrated in both animal and human studies. 20,21 To our knowledge, the only study testing a noninvasive closed-loop system in humans is a recent feasibility study showing that motor-imagery induced desynchronization detected by surface EEG can trigger transcranial magnetic stimulation (TMS) leading to increased excitability of the motor cortex.…”