Automatic artifact suppression in simultaneous tDCS-EEG using adaptive filtering

Abstract

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation method that can be used in cognitive and clinical protocols in order to modulate neural activity. Although some macro effects are known, the underlying mechanisms are still not clear. tDCS in combination with electroencephalography (EEG) could help to understand these mechanisms from a neural point of view. However, simultaneous tDCS-EEG still remains challenging because of the artifacts that affect the recorded signals. In this paper, an automated artifact cancellation method based on adaptive filtering is proposed. Using independent component analysis (ICA), the artifacts were characterized using data from both a phantom and a group of healthy subjects. The resulting filter can successfully remove tDCS-related artifacts during anodal and cathodal stimulations.

Single-session tDCS over the dominant hemisphere affects contralateral spectral EEG power, but does not enhance neurofeedback-guided event-related desynchronization of the non-dominant hemisphere's sensorimotor rhythm

“…For the same reasons, we suggest that the alpha-power increase occurs during cathodal stimulation over central electrodes of the same type. This interpretation is in line with previous works [ 17 , 22 , 24 ] describing the tDCS artifact as a low-frequency power increase in the electrodes near the stimulation sites. Notably, the higher frequency component of the disturbance may be due to ongoing small voltage shifts of the stimulator to maintain a constant current despite the little changes in electrode-skin impedances [ 22 ].…”

“…One limitation of the approach described above is that the target area for stimulation is the same from which the ERD should be recorded to provide neurofeedback. However, since tDCS may induce artifacts in the EEG locations proximal to the stimulation electrode [ 17 , 24 ], it is not possible, at least with a traditional 2-channel tDCS device, to perform neurofeedback training during stimulation, unless the stimulation electrode is placed in a non-optimal site, which could decrease the efficacy of tDCS [ 17 ]. This situation is typically solved by performing tDCS stimulation first, followed by neurofeedback training [ 14 – 16 , 19 , 25 ].…”

Low intensity transcranial electric stimulation: Safety, ethical, legal regulatory and application guidelines

“…Electrophysiological assessment methods, such as EEG or magnetoencephalography (MEG), can be used sequentially or simultaneously (provided detailed attention to potential artifact; Noury et al, 2016) to monitor the effects and efficacy of tACS on brain activity (Antal et al, 2008a; Zaehle et al, 2010) similarly to tDCS (Cunillera et al, 2016; Faria et al, 2012; Luft et al, 2014; Mancini et al, 2015). Recording electrophysiological data during stimulation requires methods for artifact elimination (Helfrich et al, 2014; Neuling et al, 2015).…”

Transcranial direct current stimulation for the treatment of motor impairment following traumatic brain injury

“…EEG with dry electrodes having the acceptable impedance level could improve the usability in a real clinical setting [79]. However, in case of simultaneous EEG-tDCS use, the EEG signal should be carefully analyzed, considering the potential signal artifacts generated by tDCS [80]. Functional near infrared spectroscopy (fNIRS) can be also used simultaneously with tDCS.…”