Immersed in Media: Telepresence Theory, Measurement & Technology by

Language: eng
Format: azw3
Publisher: Springer International Publishing
Published: 2015-06-17T16:00:00+00:00

Other Brain-Related Measures

MEG is based on the recording of the weak magnetic induction that is produced by neural currents. Because of high temporal resolution, MEG is an ideal method for studying the dynamics of neural activity. To our knowledge, MEG has not been used in studying the sense of presence to date.

In PET and fMRI, local hemodynamic changes are investigated. Of these two methods, fMRI is more widely used. Spatial resolution of fMRI is very high, while temporal resolution is limited. Interpretation of fMRI data is complicated, since the relationship between the neurochemical changes and the underlying neural activity is rather complex.

It would be a difficult task to produce a sense of presence during an fMRI for several reasons (Hoffman et al. 2003). For example, the participant has to stay immobile during the measurement, the scanner makes loud noises, and the participant is laying inside a magnet tube, which may be unpleasant. In addition, the magnetic field may interfere with the equipment that are used in the presentation of the media stimulus.

There are, however, some findings (Hoffman et al. 2003; Bouchard et al. 2009) suggesting that fMRI may be a valuable tool in presence research. Hoffman et al. (2003) proposed that a strong sense of presence could be experienced during an fMRI despite the above-mentioned constraints. Bouchard et al. (2009) found that parahippocampal cortex was significantly activated by the high presence condition.

Beeli et al. (2008) tested whether transcranial direct current stimulation (tDCS) is able to affect brain activation during the confrontation with a virtual stimulus (Beeli et al. 2008). It was, however, found that tDCS to the right dorso-lateral prefrontal cortex was not able to modulated the experience of presence while watching a virtual roller coaster ride. It may be possible that stimuli were not optimal for these purposes since there was no difference in self-reported presence either.

Variations in cerebral blood flow velocity (BFV) measured with Transcranial Doppler (TCD) sonography has widely used as a psychophysiological method to measure cognitive performance. Since TCD sonography is quite non-invasive, and there is no need to sit in an uncomfortable immobile position for a lengthy periods of time, it is a suitable psychophysiological tool for study presence in VR environments. Since neural activity is recorded from a quite large cortical area, the spatial resolution of the method is low, however. Rey et al. (2010) studied mean BFV variations when participants had to move through a VR setting with two different levels of immersion. It was found that the variations were larger in more immersive experimental conditions. Rey et al. (2011) have also studied mean BFV responses during breaks in presence in a virtual environment and, for example, found a significant difference among the maximum percentage BFV variations induced by breaks of different intensity.

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