When confronted with well-designed virtual reality (VR) scenarios, many people experience a subjective sense of actually being in the VR environment while transiently being unaware of the technology that delivers the stream of virtual input to the senses. This specific feeling has been coined “spatial presence” (SP) [1
]. This definition of SP emphasises the important role of spatial cues and the subjective strategy involved in recruiting attentional resources for processing sensory input (perception-oriented approach). An alternative view has been proposed by Sanchez-Vivez and Slater [4
]. They underline the particular contribution of supported actions in the real or virtual environment (VE) as a constituent feature of the experience of reality. They argue that the sense of “being there” in a VE is strongly grounded on the ability “to do there” (action-oriented approach).
In the context of a more recent theoretical paper, both approaches are combined and extended [5
]. In this theoretical account, a psychological construct referred to as “egocentric reference frame” (ERF) is used to explain SP. An ERF is a mental model of the world organised from a first-person perspective and contains information about the spatial properties of the immediate surroundings. A mediated environment (e.g. VR) offers an alternative ERF to the users’ real-world ERF. The sense of SP emerges if this alternative ERF is chosen as the primary ERF over the competing ERF of the real physical world. The outcome of this selection process is considered to be based on two critical questions: whether a person perceives himself 1) as if actually located in the mediated environment (self-location
) and 2) as being able to act in the mediated environment (possible actions
Only a few studies to date have examined the neural underpinnings of SP. For example, Baumgartner et al. [6
] identified a distinct network of fronto-parietal brain regions involved in the generation and regulation of SP during exposure to virtual roller coaster scenarios. Using EEG [6
], they found activations in parietal brain regions and deactivations in frontal brain regions in participants experiencing high SP compared with participants experiencing low SP. They concluded from their findings that spatial cues presented in the roller coaster scenario generate a sense of SP by strongly activating parietal brain regions (in the dorsal visual stream particularly) that thus lead to enhanced egocentric processing of the displayed environment. In a subsequent fMRI study [7
], they concluded that frontal (de)activations relating to differences in SP are closely associated with modulatory processes in the dorsolateral prefrontal cortex (DLPFC). Specifically, they concluded that activation in the DLPFC modulates the sense of SP by down-regulating egocentric visual processing in the dorsal visual stream, as reflected in those participants who experience low SP. This interpretation has received support by further studies using EEG [8
] and transcranial direct current stimulation (tDCS) [9
], the latter relating these ideas to neuroscientific concepts of behaviour and impulse control [for review, see [10
]], and by an interesting study investigating flow experience during video game playing [11
Considering the increasing importance of VR in our society (e.g. in TV, video gaming and the internet), this study aimed to extend our understanding of SP by investigating the neural correlates of the theoretically proposed key stages in the formation of SP. It was decided to experimentally influence the choice of the virtual ERF as the primary ERF by manipulating the impression of self-location
on the one hand and the perceived possible actions
on the other hand. To do so, the two important media factors perspective
(first-person perspective vs. third-person perspective) and agency
(being the agent of the actions in the VR vs. being the observer of the actions in the VR) were experimentally controlled and manipulated. These two factors have been shown to influence experience of SP in various psychometrical and behavioural studies [12
]; however, no study has investigated their influence on SP on a neural level. Thus, the present study sought to establish how manipulating the factors perspective
would influence the impression of self-location
and the perceived possible actions
and the formation of SP on a perceptual and a neural level.
To investigate this, electroencephalography (EEG) was recorded and subjective SP experience was assessed while participants played the commercially available video game “The elder scrolls 4: Oblivion”. Participants had to play a simple, non-arousing task, in which they were required to navigate the video game’s avatar (i.e. the virtual character) to a given location in four different conditions (i.e. in a 2x2 design combining the factors perspective
). The two perspective
conditions entailed playing in the 1PP or in the 3PP. The two agency
conditions allowed participants to either actively control the avatar (active) or to passively observe the avatar while it was in fact controlled by another player (passive). EEG registration was chosen over fMRI measurements to facilitate presentation of a real-life gaming situation and because EEG has been shown to be a valuable tool in the study of video and computer gaming in previous research [14
]. In order to directly compare our EEG results with the previously obtained functional magnetic resonance imaging (fMRI) and tDCS findings of our group [7
], the sLORETA software (standard low-resolution brain electromagnetic tomography) was used also in order to calculate the cortical sources [16
]. Based on previous studies, it was hypothesized that manipulating the factors perspective
influences SP by either directly or indirectly modulating the ego-centric processing in the dorsal stream. The following predictions were thus formulated for our EEG experiment:
H1: Playing the video game under 1PP compared with 3PP will enhance the experience of SP and reveal stronger activation in parietal areas (especially in the dorsal visual stream).
H2: Actively playing the video game compared with passively observing it will enhance the experience of SP and show stronger deactivation in frontal brain areas (e.g. in the DLPFC).