Differential effects of transcranial current type on heart rate variability during emotion regulation in internalizing psychopathologies.

BACKGROUND: Internalizing psychopathologies (IPs) are characterized by disruptions in emotion regulation (ER). A potential target for ER modulation in individuals with IPs is the theta band. We hypothesized that offset theta-tACS (transcranial alternating current stimulation) would result in more enhanced ER, indexed by greater increase in heart rate variability (HRV), than transcranial direct current stimulation (tDCS) in participants with IPs. METHODS: This pilot study utilized a double-blind, pseudo-counterbalanced design. Participants with internalizing psychopathologies (anxiety and depression) were randomly assigned to receive either offset theta-tACS (n = 14) or tDCS (n = 15) and underwent four sessions of stimulation (two sham). In both arms, there were alternating iterations of an emotion regulation task (ERT) during or immediately after stimulation and rest. Heart rate data were collected during each ERT and rest iteration, and analyses were completed using high-frequency (HF) and root mean square of successive differences (RMSSD) HRV metrics. RESULTS: tACS participants consistently displayed increases in both HRV metrics from Time 1 to Time 4. Participants receiving tDCS displayed few significant changes in HF-HRV and no significant changes in RMSSD-HRV. LIMITATIONS: Due to the small sample size, analyses were limited. Additionally, the lack of a baseline ERT makes it difficult to determine overall ER improvement. CONCLUSIONS: tACS appears to increase ER capacity as reflected in increased HRV in individuals with internalizing psychopathologies, particularly after two sessions of stimulation. This study adds validity to the use of tACS as a neuromodulatory technique in cognitive and clinical research. Additional research is required to better understand potential carry-over effects of multiple sessions of stimulation.

Neuromodulatory effects of transcranial electrical stimulation on emotion regulation in internalizing psychopathologies.

OBJECTIVE: We hypothesize offset theta-tACS (transcranial alternating current stimulation) improves emotion regulation (ER) and psychopathology more than transcranial direct current stimulation (tDCS) in participants with internalizing psychopathologies (IPs). METHODS: This pilot study utilized a double-blind, pseudo-counterbalanced, sham-controlled design with participants with IPs. Participants were assigned to receive tDCS or tACS, underwent four stimulation sessions (two sham), and completed an emotion regulation task (ERT) during or after stimulation. Participants completed the Beck Depression Inventory before/after the study, the Spielberger State and Trait Anxiety Index after each ERT, and rated their arousal, valence, and perceived reappraisal ability during the ERT. RESULTS: Participants receiving either stimulation type showed a reduction in anxiety, depression, and valence and arousal ratings. We additionally discovered an effect demonstrating those who received sham stimulation first displayed little-to-no change in any score across the study, but tACS participants who received verum stimulation first showed significant improvements in each metric. CONCLUSIONS: Improving ER capabilities via theta tACS has the potential to yield beneficial clinical effects. SIGNIFICANCE: This study adds validity to the use of non-invasive neuromodulatory methods, especially tACS, to alleviate IPs. Additional research is needed to better understand the effects of sham stimulation. Careful consideration of sham incorporation should be made in future studies.