FIGURE 1.

The biofeedback loop. Biofeedback is a form of human-computer interaction which puts the user in a closed real-time loop. We divide this loop in three components that are discussed throughout the paper. First, a biofeedback parameter (A) is extracted from a physiological modality. For example, heart rate derived from an electrocardiogram. Second, in a series of processing steps (B) the current state of the parameter is evaluated relative to a target state. The processing results in a biofeedback score that expresses how well the parameter’s current state matches the target state. The biofeedback score can be qualitative (match vs. no match) or quantitative (degree of matching). Finally, the biofeedback score is translated into a representation (C) consisting of (a combination of) visual, auditory, or tactile feedback which can be embedded in a variety of media, such as VR.