Electrophysiological evaluation of high and low-frequency transcranial random noise stimulation over the auditory cortex.

BACKGROUND

Transcranial random noise stimulation (tRNS) is a non-invasive brain stimulation technique which uses electrical alternating currents applied at random frequencies. Besides the ability to alter cortical excitability, past research demonstrated that high-frequency tRNS over the auditory cortex can modulate both spontaneous and auditory evoked oscillatory brain activity.

OBJECTIVES

The aim of the present study was to examine the effects of high- and low-frequency auditory tRNS on EEG power and evoked activity.

METHODS

Low-frequency (0.1-100Hz), high-frequency (100-640Hz) and sham tRNS were administered for a stimulation over the auditory cortex in 22 healthy subjects. Before and after tRNS stimulation auditory steady state responses (ASSR) of 20 and 40Hz stimuli as well as oscillatory brain activity were recorded with electroencephalography (EEG).

RESULTS

Stimulation of both verum tRNS protocols revealed no significant changes either in ASSR or in resting state EEG activity. Unexpectedly, sham tRNS resulted in a significant decrease in 20Hz ASSR and an increase in the alpha frequency band (8-12.5Hz).

CONCLUSION

We were not able to replicate previous findings of a modulation of resting state EEG activity and ASSR by tRNS.