Poster Session A, Saturday, March 23, 1:30 pm - 3:30 pm, Pacific Concourse
Modulation of auditory gamma-band responses using transcranial electrical stimulation
Kevin Jones1, Zoë Tauxe1, Elizabeth Johnson2,3, Donald Rojas1; 1Colorado State University, 2University of California, Berkeley, 3Wayne State University
Auditory gamma-band (>30 Hz) activity in the electroencephalogram (EEG) is widely studied as a marker of cortical excitation and inhibition balance in disorders such as autism and schizophrenia, and in recovery from depression. Specifically, reduced gamma-band activity is considered a marker of reduced inhibition and hyperexcitability. By applying very weak electrical currents to the brain, non-invasive neurostimulation techniques such as transcranial alternating current stimulation (tACS) and transcranial direct current stimulation (tDCS) have been shown to temporarily modulate cortical excitation and inhibition levels. Importantly, it stands to reason that this clinical gamma-band biomarker could be altered with the use of non-invasive neurostimulation. Here, we investigated whether gamma-band responses can be directly modulated with tACS and/or tDCS, as compared to sham stimulation, in a sample of 45 healthy undergraduates. Participants underwent 200 trials of 40-Hz auditory clicks while scalp EEG data were collected to measure gamma activity. Participants then received 10 minutes of 1 mA tACS (40 Hz), tDCS, or sham stimulation to the left auditory cortex. Immediately following stimulation, participants underwent the auditory task while EEG data were collected a second time. Participants who received tACS exhibited widespread increases in gamma power and phase-locking to the auditory stimulus. These effects were absent in the tDCS and sham groups. These results demonstrate that one of the most prominent biomarkers of clinical disorders can be directly modulated with gamma tACS. We suggest that augmenting treatment regimens with non-invasive neurostimulation may lead to improved outcomes in clinical populations.
Topic Area: METHODS: Electrophysiology