Full Length ArticleTranscranial modulation of brain oscillatory responses: A concurrent tDCS-MEG investigation

- The study incorporated the simultaneous application of tDCS and MEG.
- A decline in average power within the visual gamma band was noted for anodal tDCS.
- Motor evoked response magnitude was enhanced during anodal tDCS.
- MEG can be used to derive inferences on the cortical mechanisms of tDCS.
- Metrics of electrophysiology are implicated in the generation of tDCS effects.

Despite the increasing use of transcranial direct current stimulation (tDCS), the physiological mechanisms underlying its effects are still largely unknown. One approach to directly investigate the effects of the neuromodulation technique on the brain is to integrate tDCS with non-invasive neuroimaging in humans. To provide new insight into the neurobiology of the method, DC stimulation (1 mA, 600 s) was applied concurrently with Magnetoencephalography (MEG), while participants engaged in a visuomotor task before, during and after a period of tDCS. Responses in the motor beta band (15-30 Hz) and visual gamma band (30-80 Hz) were localised using Synthetic Aperture Magnetometry (SAM). The resulting induced and evoked oscillatory responses were subsequently analysed. A statistically significant reduction of average power in the visual gamma band was observed for anodal compared to sham stimulation. The magnitude of motor evoked responses was also found to be significantly modulated by anodal stimulation. These results demonstrate that MEG can be used to derive inferences on the cortical mechanisms of tDCS.