Since Virtual Reality (VR) has been used as a non-pharmaceutical adjunct to pain management, the analgesic effect of VR has been widely demonstrated in various pain conditions. However, there is no consensus on what kind of VR content is the best for pain alleviation and by what means VR modulates pain perception. To address these issues, the present study included three progressive experiments to explore the effect and neural mechanisms of VR-induced analgesia on contact heat pain by electroencephalogram (EEG).
In a behavioral study (Experiment 1), fixed temperature stimuli (6/10 points for each participant) were delivered to the right forearm of 31 heap场subjects, and subjective pain intensity, unpleasantness, positive and negative emotions before and after interventions were compared in VR (multisensory information were presented), 2D (the same video as in VR was presented through a computer screen), and Control (no video was presented) intervention conditions. Results showed that the multisensory experience of VR effectively lowered the pain intensity and unpleasantness, maintained positive emotion, and reduced negative emotion.
In an EEG study (Experiment 2) with the same design as in Experiment 1,data were collected from 24 healthy subjects. In addition to similar behavioral results as in Experiment 1,the reduction of contact heat stimuli evoked P2 responses were observed in the present experiment. Moreover, the reduced pain intensity rating was correlated with decreased P2 amplitude and increased spontaneous gamma oscillations, and the link between gamma oscillation and pain intensity was mediated by P2 amplitude, which suggested a possible neural pathway to explain the VR-induced analgesia.
To explore the effects and neural mechanisms of analgesia induced by different VR scenes, an additional 24 subjects were recruited in Experiment 3.Results showed that VR scenes designed for distraction and mindfulness were associated with distinct neural mechanisms, but the analgesic effects were comparable. Specifically, distraction VR scene induced a sustained attention on multisensory information and enhanced spontaneous gamma oscillations, which further influenced pain processing; mindfulness VR scene was helpful to entered mindfulness state for subjects which was associated with the increase of alpha oscillation, produced an analgesic effect by affecting their own state.
These results suggested that VR involved a top-down analgesic mechanism and different VR scenes were associated with different neural mechanisms. These results will help to understand the mechanisms of VR induced analgesia and develop more VR scenes for different pain conditions, facilitate the development of digital healthcare and help more patients to return to normal life.
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