tDCS Modulates Visual Gamma Oscillations and Basal Alpha Activity in Occipital Cortices: Evidence from MEG.
Transcranial direct-current stimulation (tDCS) is now a widely used method for modulating the human brain, but the resulting physiological effects are not understood. Recent studies have combined magnetoencephalography (MEG) with simultaneous tDCS to evaluate online changes in occipital alpha and gamma oscillations, but no study to date has quantified the offline (i.e., after tDCS) alterations in these responses. Thirty-five healthy adults received active or sham anodal tDCS to the occipital cortices, and then completed a visual stimulation paradigm during MEG that is known to elicit robust gamma and alpha oscillations. The resulting MEG data were imaged and peak voxel time series were extracted to evaluate tDCS effects. We found that tDCS to the occipital increased the amplitude of local gamma oscillations, and basal alpha levels during the baseline. tDCS was also associated with network-level effects, including increased gamma oscillations in the prefrontal cortex, parietal, and other visual attention regions. Finally, although tDCS did not modulate peak gamma frequency, this variable was inversely correlated with gamma amplitude, which is consistent with a GABA-gamma link. In conclusion, tDCS alters gamma oscillations and basal alpha levels. The net offline effects on gamma activity are consistent with the view that anodal tDCS decreases local GABA.
Department of Neurological Sciences, University of Nebraska Medical Center (UNMC), Omaha, NE, USA.|Department of Pharmacology and Experimental Neurosciences, UNMC, Omaha, NE, USA.|Center for Magnetoencephalography, UNMC, Omaha, NE 68198, USA.
Tony W
TW
Wilson
Center for Magnetoencephalography, UNMC, Omaha, NE 68198, USA.
Timothy J
TJ
McDermott
Center for Magnetoencephalography, UNMC, Omaha, NE 68198, USA.
Mackenzie S
MS
Mills
Center for Magnetoencephalography, UNMC, Omaha, NE 68198, USA.
Nathan M
NM
Coolidge
Department of Neurological Sciences, University of Nebraska Medical Center (UNMC), Omaha, NE, USA.|Center for Magnetoencephalography, UNMC, Omaha, NE 68198, USA.
Elizabeth
E
Heinrichs-Graham
D000328:Adult; D000513:Alpha Rhythm / Q000502:physiology*; D001931:Brain Mapping; D005260:Female; D007839:Functional Laterality; D065818:Gamma Rhythm / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D009778:Occipital Lobe / Q000000981:diagnostic imaging / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D013997:Time Factors; D065908:Transcranial Direct Current Stimulation / Q000379:methods*; D055815:Young Adult