The Role of Theta Synchrony in Emotion Dysregulation in Internalizing Psychopathologies

Individuals with Internalizing Psychopathologies (IPs) experience difficulties regulating their emotions to meet contextual demands. The dorsolateral prefrontal cortex (dlPFC), implicated in emotion regulation (ER), is hypoactive in IP individuals. A potential new target for ER modulation is theta band synchrony, which increases during ER. Importantly, individuals with IPs display hypersynchronous theta bands while at rest. We posit that this hypersynchrony may create a ceiling effect in the theta band, limiting their capacity to synchronize and desynchronize as necessary, leading to emotion dysregulation. The present study investigated the effects of dlPFC-targeting transcranial direct current stimulation (tDCS) in parallel with individualized offset theta-tACS (transcranial alternating current stimulation) in individuals with IPs in an ER context. Thirty-three IP participants were randomly assigned to receive 4 sessions (2 sham, 2 verum) of either tACS or tDCS and completed 4 iterations of an emotion regulation task (ERT) during or immediately following stimulation. EEG was recorded during tasks without stimulation. Anxiety was assessed before the study and after each Rest+ERT pair, depression was assessed before and after the study, and subjective ratings of valence and emotional arousal were reported throughout the ERTs. Heart rate variability (HRV) – a metric of ER capacity – was calculated for each Rest and ERT. tACS delivered at participants’ highest-synchrony edge successfully reduced synchrony at the stimulated edge whereas tDCS did not, as expected. Participants in both groups displayed significant decreases in anxiety and depression scores, particularly tACS participants who received verum first. Both groups displayed decreases in valence, but only tACS participants showed decreases in arousal. tACS participants additionally displayed significant increases in HRV over the course of the study. Though synchrony decreases did not correlate with changes in clinical metrics, decreases significantly correlated with increases in HRV, indicating improved ER capacity. Our results suggest that by targeting theta hypersynchrony, we could improve ER capacity moreso than by targeting dlPFC hypoactivity. Future work will continue investigating the effects of individualized theta-tACS in IP individuals and will extend this investigation to include examination of potential build-up effects of multiple sessions of stimulation and any “real world” lasting effects.