Interplay between Alpha Oscillations, Anxiety, and Sensory Processing

Alpha oscillations (8-12 Hz) have been implicated in sensory processing and the inhibition/filtering of irrelevant sensory input. Meanwhile, aberrations in sensory filtering have been associated with a number of conditions, including anxiety and posttraumatic stress disorder (PTSD). The latter can be characterized by pathologically diminished levels of alpha power and posterior→frontal alpha connectivity, but the role of alpha oscillations in other anxiety disorders remains to be elucidated. In this experiment we set out to test the effect of both anxiety and alpha activity on sensory processing in the auditory modality, as well as investigate the potential relationship between these two variables. We manipulated anxiety via a 5 minute anxiety induction and attempted to manipulate (increase) alpha power and posterior→frontal alpha connectivity via 20 minutes of transcranial alternating current stimulation (tACS). The anxiety induction led to increases in anxiety, and resulted in a general increase in rated intensity and a corresponding decrease in rated pleasantness of sounds. This effect further interacted with the intensity and valence of the auditory stimuli. No changes in alpha power or posterior→frontal alpha connectivity were observed as a result of the anxiety induction. The tACS treatment failed to result in significant increases in alpha power and posterior→frontal alpha connectivity, and did not lead to significant changes in mood. However, posterior→frontal alpha connectivity significantly decreased in the sham condition, while no such decrease was observed in the tACS group. In addition, it was found that rated pleasantness of quiet sounds decreased in the sham condition but not in the tACS condition following treatment, potentially hinting at a buffering effect of tACS. In conclusion, we were able to demonstrate a link between anxiety and sensory processing in the auditory modality, while the relationship between alpha activity and anxiety (if one exists) remains uncertain.