Neural correlates of "absence" in interactive simulator protocols.

While much has been written about the importance of the experience of presence in simulation protocols, the role of "absence" deserves closer attention. The role of subjective experience and neurophysiologic processes involved in fluctuating states of consciousness is a key issue in developing assessment and treatment tools using interactive immersive simulator tasks. This paper proposes that when engaging in an interactive simulator task, there are fluctuations of consciousness that determine both motivational engagement and measured performance. Rather than expecting a continuous experience, both in terms of perceptual and motor output flow, factors such as circadian fluctuations, fatigue, and actual intrusion of sleep into waking consciousness are relevant in assessments and treatments using virtual environment-based tasks. These factors are particularly relevant in treatment populations with neurological and psychiatric disorders, where such disturbances are more common. To illustrate this construct, a series of experiments examining these phenomena in relation to a standardized driving-simulation protocol to detect psychomotor impairment developed for clinical and diagnostic testing in a sleep laboratory setting are reviewed.