Virtual reality environmental enrichment effects on heart rate variability in healthy volunteers

Environmental enrichment (EE) is a nonpharmacological approach widely used in preclinical studies and only recently applied to humans using virtual reality (VR). Virtual EE has been shown to decrease basal cravings for smoking and palatable food; however, little is known about what processes are affected by EE. One hypothesis is that it may affect participants' emotional state (stress- relief hypothesis).

We aimed to investigate whether physiological parameters of stress response are modified by virtual EE by assessing heart rate variability (HRV) in healthy volunteers. Second, we explored psychological measures of affective and mood states associated to virtual EE and assessed the correlation of HRV to measures of locomotion and interaction in the virtual simulation.

Twenty healthy volunteers (11 men) were exposed to a virtual EE and Control Environment (CE), in counterbalancing order. HRV and participants' behavior were measured during VR exposure. Self-report measures of mood, arousal, pleasantness and immersion were also collected before and after VR.

Participants showed a significant increase in time-domain HRV (RMSSD), but not in frequency-domain (HF and LF/HF ratio) measures, and self-report measures (pleasantness, activation, positive mood and perception of immersion) in EE vs. CE. Positive correlations between the score of immersion in the VR simulation and HRV indexes emerged in EE scenario only.

The results showed an improvement in subjectively reported emotional state and an increase in parasympathetic component of HRV, suggesting that the mechanism underlying the EE effects found in this and previous work may be due to decreased stress, consistent with the "stress-relief" hypothesis.