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Dorokhov Vladimir B.
Institute of Higher Nervous Activity and Neurophysiology RAS,
Moscow, Russia (vbdorokhov@mail.ru).

Efforts to apply virtual reality technology to advance the fields of medicine, education, engineering, design, training, and entertainment are currently underway. The effectiveness of virtual environments (VEs) has often been linked to the sense of presence reported by users of those VEs. Presence is defined as the subjective experience of being in one place or environment, even when one is physically situated in another. The presence phenomenon is at the centre of psychological research in VEs. The presence is a normal awareness phenomenon that requires directed attention and is based in the interaction between sensory stimulation, environmental factors that encourage involvement and enable immersion, and internal tendencies to become involved. The study of neural correlates of presence is necessary for developmental neurobiology-based theory of presence. IJsselsteijn (2002) writes: " ... the exact nature and location of the processing that results in a sense of presence is not known. It appears that the presence experience has a potentially large number of neural processes associated with it. Any attempt to 'localize' the presence experience is not unlike attempts at localizing consciousness, or intelligence. To paraphrase William James, presence is not a thing, but a process. Exactly what that process is, still remains to be discovered".

Now many authors believe that sense of presence could appear in three cases: in a real world, in a virtual world, and in an internal mental world. Riva and Waterworth (2003) suppose that presence is the result of the evolution of the central nervous system in its attempt to embed the sensory-referred properties into an internal functional space. As noted by Waterworth and Waterworth (2003), the appearance of the sense of presence allows the nervous system to solve a key problem for its survival: how to differentiate between internal and external states.

In our opinion, the essential contribution to development of neurobiology-based theory of presence can be brought by studies of sleep/wake transitions. Analyzing the transition from wake to sleep, many researchers allocate a drowsiness state as an independent condition which is distinct from both wake and sleep, regarding to physiological as well as on psychological parameters. During the period of drowsiness there is a change of a state of consciousness at which the attention is switched from external environment to internal information processes that rather frequently is accompanied by occurrence of hypnagogic images.

We have developed continuous psychomotoric test carried out with closed eyes. Visual sensory isolation (closed eyes) from surrounding real world caused quick development of drowsiness and the appearance of erroneous performance. A level of presence in a real world was estimated by continuous performance of test (self-pacing button pressing). Healthy subjects (n=64) participated in experiments (n=280) and EEG, ECG, EOG, skin conductance response (SCR) and button pressings were recorded. The error onset was shown to be preceded by the EEG "drowsy pattern" and decreased in the rate of spontaneous SCR. The performance reappearance after the self-detected error was accompanied by phasic SCR and alpha-burst of EEG. When participants spontaneously self-activated and renewal of proper performance, he/she reported about "...lost in thought" and dream-like imagery and after that announce of the perception of the errors. The interval between the error and the first following SCR (mean 10.1 s) was significantly (p<0.001) shorter than the interval between the error and the last preceding SCR (mean 69.8 s).

It is supposed that the subjective perception of an error is a significant endogenous stimulus which evokes the orienting response (OR) and accompanying by SCR (sympathetic activation). The spontaneous restoration of performance and self-detected error is an analogue of the break out of their state of presence (break in presence - BIP) in "internal worlds" to back to the "real world" (Slater & Steed, 2000). These moments when individual switches from one interpretation of environment to another, are of particular interest. If it could be known when and why it occurred, this would be a major contribution to the problem of eliciting the factors that enhance or inhibit the sense of presence. We also believe that our approach to BIPs measuring by physiological registration of phasic OR components (Sokolov E.N.) might be used for the analysis of human performance efficiency in the virtual reality systems.

This research was support by the Russian Humanitarian Foundation ( 01-600186)


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