Autonomic nervous system reactivity to positive and negative mood induction: the role of acute psychological responses and frontal electrocortical activity.

The differential effects of positive versus negative emotions on autonomic nervous system activity are insufficiently understood. This study examined the role of acute mood responses and central nervous system activity on heart rate variability (HRV) using 5-min event recall tasks (happiness and anger recall) and a 5-min Stroop Color Word Test (SCWT) in 20 healthy individuals (mean age 25 ± 4 years, 55% female). HRV was measured in high frequency (HF) and low frequency (LF) domains, and frontal brain activity using electroencephalography (EEG) in the alpha frequency band in F3 and F4. Happiness Recall resulted in increased LF-HRV (p = 0.005) but not HF-HRV (p=0.71). Anger Recall did not change HRV (p-values > 0.10). The SCWT produced decreases in HF-HRV (p = 0.001) as well as LF-HRV (p = 0.001). The magnitude of feeling "happy" during Happiness Recall was positively correlated with ΔHF-HRV (p = 0.050), whereas an incongruent mood state ("frustrated") was associated with smaller ΔHF-HRV (p = 0.070). Associations between frontal EEG activation and HRV responses were mostly non-significant, except for increased right frontal activation during Happiness Recall which was associated with a decrease in LF/HF ratio (p = 0.009). It is concluded that positive and negative mood induction result in differential HRV responses, which is related to both task valence and the intensity of task-induced emotions.