P146. Comparison of alpha-entrainment with oscillatory and noisy low-voltage stimulation

Introduction Non-invasive brain stimulation is an emerging field in clinical neurology. Frequency- and noise specific stimulation can induce specific oscillatory activity patterns that are associated with a recovery-related brain state. However, our understanding of the underlying neurophysiological mechanisms remain incomplete, which is a major limitation for transitioning into clinical practice. One notion is the existence of a common framework with oscillatory and noisy components. Here, we studied the influence of a random noise stimulation with added alternating current stimulation in the retinofugal pathway on the entrainment of alpha-power over the visual cortex. Methods We applied retinofugal alternating current stimulation (rtACS) in each subject’s individual alpha-frequency (IAF) and retinofugal random noise stimulation (rtRNS) on 10 healthy subjects. Varying current intensities were applied over a stimulation period of 30 s followed by a 40 s free interval respectively. EEG measurements were recorded prior, during and after stimulation over a total duration of 12 min. Results rtACS in IAF entrains occipital alpha power with increasing stimulation intensity. rtRNS has strong facilitatory effects on alpha activity ( p p = 0.069). Discussion As random noise stimulation improved alpha power in all intensity ranges while showing a trend towards inhibiting alpha activity in combination with oscillatory stimulation, we argue that our findings are suggestive of noise acting as a controller of oscillations in neural networks. Hence, a common framework consisting of oscillatory and noisy stimulation might modify brain-states more effectively.