Prim JH, et al. - Researchers examined how non-invasive brain stimulation affects the autonomic nervous system (ANS) via analyzing heart rate variability (HRV) metrics obtained in a previously published study of transcranial alternating current stimulation (tACS) for the modulation of chronic low back pain through enhancing alpha oscillations. It is assumed that respiratory sinus arrhythmia (RSA) would increase with tACS. In this randomized, crossover, double-blind, sham-controlled pilot study, metrics of ANS balance were calculated from electrocardiogram (ECG) following 10Hz-tACS. Before and after 40 mins of 10Hz-tACS or sham stimulation, they collected ECG data for 2 mins. Outcomes revealed no significant increase in RSA following tACS, however, the exploratory analysis suggested a significant rise in the standard deviation of normal intervals between R-peaks, a measure of ANS balance, for 10Hz-tACS relative to sham. This indicated the modulatory effect of tACS on an integrated HRV measure of both ANS branches.