Transcranial alternating current stimulation ameliorates emotional attention through neural oscillations modulation.

Background: Numerous clinical reports have suggested that psychopathy like schizophrenia, anxiety and depression is accompanied by early attentional abnormalities in emotional processing. Recently, the efficacy of transcranial alternating current stimulation (tACS) in changing emotional functioning has been repeatedly observed and demonstrated a causal relationship between endogenous oscillations and emotional processing. Aims: Up to now, tACS effects on emotional attention have not yet been tested. To assess such ability, we delivered active-tACS at individual alpha frequency (IAF), 10 Hz or sham-tACS for 7 consecutive days in the bilaterally dorsolateral prefrontal cortex (dlPFC) to totally 79 healthy participants. Results: IAF-tACS group showed significant alpha entrainment at-rest, especially in open state around stimulation area and showed an obvious advantage compared to 10 Hz-tACS. Event-related potential revealed a significant larger P200 amplitude after active-tACS and IAF group showed wider range of emotions than 10 Hz-tACS, indicating the attentional improvement in facial emotion processing. A notable positive correlation between alpha power and P200 amplitude provided an electrophysiological interpretation regarding the role of tACS in emotional attention modulation instead of somatosensory effects. Conclusion: These results support a seminal outcome for the effect of IAF-tACS on emotional attention modulation, demonstrating a feasible and individual-specific therapy for neuropsychiatric disorders related to emotion processing, especially regarding oscillatory disturbances.

Modulating emotion processing using transcranial alternating current stimulation (tACS) - A sham-controlled study in healthy human participants.

As an emerging non-invasive neuromodulation technique, transcranial alternating current stimulation(tACS) has been reported to be used in mood regulation, cognitive modulation and brain trauma recovery by applying specific frequency currents. However, the neuromodulatory mechanisms and effects of tACS on emotion processing are unclear. In this study, a single-blind experiment with 44 healthy subjects in 1:1 randomized groups (experimental group given 10 Hz-tACS and control group given sham-stimulation) was conducted. The effects of tACS applied to the prefrontal lobe on the brain's emotional state and emotional cognitive processing in response to emotional stimulation patterns were explored by designing two experimental paradigms of an 8-minute open and closed eye resting task and an emotional face oddball task. Power spectrum and event-related potentials were extracted to explore the effect of tACS on brain rhythm modulation and attention modulation. It was found that the experimental group showed significantly enhanced alpha rhythm in the whole brain range after tACS, especially in the parieto-occipital lobe. The rate of misclassification of neutral emotions into negative emotions was significantly lower and the amplitude of P2 and P3 of event-related potentials were significantly higher when performing the emotional face task after tACS, while the control group did not have this phenomenon. These results suggest that tACS can modulate and enhance alpha rhythm activity by synchronizing alpha oscillations in the frontoparietal attention network, thereby improving subjects' negative emotion cognitive bias and enhancing their emotion processing by increasing early and late levels of emotional attention.