Neurofeedback in Virtual Reality Naturalistic Scenarios for Enhancing Relaxation: Visual and Auditory Stimulation to Promote Brain Entrainment

Biofeedback is a procedure aimed at increasing a subject's proprioception based on the principle of "physiological mirroring". The subject has the opportunity to receive visual and/or auditory feedback in real time correlated to one or more physiological parameters acquired. The goal is to find a strategy to modify these parameters and learn from the feedback received to have a greater awareness of his/her own body. The various biofeedback trainings aim to normalize the functional state of the various body systems such as the central nervous system (CNS), the cardiovascular system, and others. In Neurofeedback, in particular, the subject is provided with real-time information on his/her brain rhythms (EEG) and brain functioning; the brain, thanks to its neuroplasticity, takes note of this information and gradually modulates its activity in response to it. The main weakness of neurofeedback treatment is that simple and uninteresting designs can demotivate or exhaust the patient during training sessions. The creation of scenarios in virtual reality turns out to gain more interest in the patient, making the treatment more immersive and therefore more engaging. The purpose of this study is to promote subject's relaxation in the shortest possible time after a stressful situation, and to support a gradual learning of how to manage his/her own brain rhythms over the course of the various training sessions. To achieve this, a virtual reality neurofeedback system, set in a naturalistic and semi-realistic scenario, was designed. To support the treatment, visual and auditory stimulation was added promoting Brain Entrainment, which is the dragging of brain waves towards a specific frequency, i.e., that of the subject's intrinsic oscillator. A Single Case Study was conducted over three weeks (three sessions per week), and robust results were obtained for the individual trainings: throughout the acquisition, a Relaxation Score, correlated to the beta-to-alpha ratio (BAR), showed an increasing trend during the stress test (BAR=1.29 ± 0.41 during the last session) and a decreasing trend during the relaxation phase (BAR=0.49 ± 0.15 during the last session), in accordance with the expected results. Furthermore, the effect of the training is shown to be long-lasting, supported by a statistically significant difference between the initial and final baselines. It is also demonstrated that, during the various trainings, the subject achieves a tendentially better Maximal Relaxation Score, also increasing the time for which she can keep the BAR below a fixed predetermined threshold. ECG signal was also evaluated in post-processing, comparing Heart Rate and Heart Rate Variability between the various phases of the training. On these parameters, results consistent with the study are obtained, but not as robust as those obtained on EEG. Further analysis is needed to determine whether the results are related to the combination of Neurofeedback and Brain Entrainment or only to one of these. The work was mainly based on the design and testing of the system, so it would be appropriate to carry out in the future a study on a larger number of subjects in order to make the results more solid. Moreover, the project paves the way for a study on subjects with generalized anxiety disorder, post-traumatic stress disorder, and other types of mental diseases.