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Cybersickness is common during virtual reality experiences with head-mounted displays (HMDs). Previously it has been shown that individual differences in postural activity can predict which people are more likely to experience visually-induced motion sickness. This study examined whether such predictions also generalise to the cybersickness experienced during active HMD-based virtual reality. Multisensory stimulation was generated by having participants continuously turn their heads from left to right while viewing the self-motion simulations. Real-time head tracking was then used to create ecological (‘compensated’) and non-ecological (‘inversely compensated’) head-and-display motion conditions. Ten (out of 20) participants reported feeling sick after being exposed to these self-motion simulations. Cybersickness did not differ significantly between the two compensation conditions. However, individual differences in spontaneous postural instability when standing quietly were found to predict the likelihood of subsequently experiencing cybersickness. These findings support recent proposals that postural measures can help diagnose who will benefit the most/least from HMD-based virtual reality.

Sensory perception is neither static nor simple. The senses influence each other during multisensory stimulation and can be both suppressive and super-additive. As most knowledge of human olfactory perception is derived from functional neuroimaging studies, in particular fMRI, our current understanding of olfactory perception has systematically been investigated in an environment with concurrent loud sounds. To date, the confounding effects of acoustic fMRI-noise during scanning on olfactory perception have not yet been investigated. In this study we investigate how acoustic noise derived from the rapid switching of MR gradient coils, affects olfactory perception. For this, 50 subjects were tested in both a silent setting and an fMRI-noise setting, in a randomised order. We found that fMRI-related acoustic noise had a significant negative effect on the olfactory detection threshold score. No significant effects were identified on olfactory discrimination, identification, identification certainty, hedonic rating, or intensity rating.

Temporal regularities can guide our attention to focus on a particular moment in time and to be especially vigilant just then. Previous research provided evidence for the influence of temporal expectation on perceptual processing in unisensory auditory, visual, and tactile contexts. However, in real life we are often exposed to a complex and continuous stream of multisensory events. Here we tested – in a series of experiments – whether temporal expectations can enhance perception in multisensory contexts and whether this enhancement differs from enhancements in unisensory contexts. Our discrimination paradigm contained near-threshold targets (subject-specific 75% discrimination accuracy) embedded in a sequence of distractors. The likelihood of target occurrence (early or late) was manipulated block-wise. Furthermore, we tested whether spatial and modality-specific target uncertainty (i.e. predictable vs. unpredictable target position or modality) would affect temporal expectation (TE) measured with perceptual sensitivity ( d ′ ) and response times (RT). In all our experiments, hidden temporal regularities improved performance for expected multisensory targets. Moreover, multisensory performance was unaffected by spatial and modality-specific uncertainty, whereas unisensory TE effects on d ′ but not RT were modulated by spatial and modality-specific uncertainty. Additionally, the size of the temporal expectation effect, i.e. the increase in perceptual sensitivity and decrease of RT, scaled linearly with the likelihood of expected targets. Finally, temporal expectation effects were unaffected by varying target position within the stream. Together, our results strongly suggest that participants quickly adapt to novel temporal contexts, that they benefit from multisensory (relative to unisensory) stimulation and that multisensory benefits are maximal if the stimulus-driven uncertainty is highest. We propose that enhanced informational content (i.e. multisensory stimulation) enables the robust extraction of temporal regularities which in turn boost (uni-)sensory representations.

Bodily boundaries are computed by integrating multisensory bodily signals and can be experimentally manipulated using bodily illusions. Research on tool use demonstrates that tools alter body representations motorically to account for changes in a user's action repertoire. The present experiment sought to unify perceptual and motoric accounts of tool embodiment using a modified Rubber Hand Illusion (RHI) that also addressed the skill and practice aspects of the tool use literature. In Experiment 1, synchronous multisensory stimulation induced perceptual embodiment of a tool, chopsticks. The embodiment of chopsticks was stronger for more skilled participants, and if the illusion was preceded by tool use. In Experiment 2, the illusion was not elicited with a different type of tool, a teacup, showing that not all objects can be incorporated. This experiment helps to clarify the role of perceptual and motoric embodiment and suggests future avenues for research into tools embodiment using this method.

Interoceptive and exteroceptive information are both essential for the construction and update of self-awareness. Whereas several studies have shown how interoceptive accuracy or cardiac feedback influences body-awareness, no studies have looked at the reverse effect, namely how exteroceptively-driven changes in body-ownership and self-identification can influence individuals' ability to detect internal bodily signals. We exposed participants to the Rubber Hand Illusion (Experiment 1) and to the Enfacement Illusion (Experiment 2), and tested how this change in the sense of body-ownership and self-identification affected their interoceptive accuracy (IAcc). The heartbeat-counting task was used to measure IAcc before the bodily illusions, and then the same task was interleaved with periods of visuo-tactile stimulation, during which synchronous and asynchronous multisensory stimulation was applied. We found that a change in body-ownership significantly improved performance of participants with lower interoceptive accuracy. In contrast, a change in self-identification significantly decreased performance of participants with higher interoceptive accuracy. These results suggest that changes in different domains of self-awareness can differentially impact individuals' ability to accurately detect signals arising from within the body, highlighting the distinct role that interoceptive signals play for different facets of bodily self-consciousness.

Our perceptual systems integrate multisensory information about objects that are close to our bodies, which allow us to respond quickly and appropriately to potential threats, as well as act upon and manipulate useful tools. Intriguingly, the representation of this area close to our body, known as the multisensory 'peripersonal space' (PPS), can expand or contract during social interactions. However, it is not yet known how different social interactions can alter the representation of PPS. In particular, shared sensory experiences, such as those elicited by bodily illusions such as the enfacement illusion, can induce feelings of ownership over the other's body which has also been shown to increase the remapping of the other's sensory experiences onto our own bodies. The current study investigated whether such shared sensory experiences between two people induced by the enfacement illusion could alter the way PPS was represented, and whether this alteration could be best described as an expansion of one's own PPS towards the other or a remapping of the other's PPS onto one's own. An audio-tactile integration task allowed us to measure the extent of the PPS before and after a shared sensory experience with a confederate. Our results showed a clear increase in audio-tactile integration in the space close to the confederate's body after the shared experience. Importantly, this increase did not extend across the space between participant and confederate, as would be expected if the participant's PPS had expanded. Thus, the pattern of results is more consistent with a partial remapping of the confederate's PPS onto the participant's own PPS. These results have important consequences for our understanding of interpersonal space during different kinds of social interactions. (C) 2014 Elsevier Ltd. All rights reserved.

Objectives Transcranial Magnetic Stimulation (TMS) is capable to non-invasively stimulate the human cortex. Electroencephalography (EEG) can record the cortical response evoked by TMS (TEPs), which are a summation of the brain responses to the TMS-induced electric field in the cortex, and to the multisensory peripheral stimulation derived from the TMS coil discharge. This multisensory stimulation is composed by a somatosensory component relative to the activation of trigeminal nerve fibers and by an auditory component due to the loud click of the coil. Here, we aim to describe the contribution of somatosensory and auditory processing to the TEPs by comparing a somatosensory-auditory sham condition with real TMS. Methods In 18 healthy individuals, TMS was delivered with a figure-of-eight coil over two target sites (parietal and frontal) using two coil orientations. On the same target sites, a sham condition was applied by delivering a cutaneous electrical stimulation concurrently with the TMS click. The EEG was recorded with a 61-channel TMS-compatible system. Results The potentials evoked by real TMS and by somatosensory-auditory sham TMS were highly similar in terms of shape and spatial distribution, particularly at later latencies, 70–200 ms, after stimulus administration. Conclusion The present results challenge a straight-forward interpretation of TEPs as an index of cortical connectivity of the focally stimulated brain region, because of the strong contribution of TMS-induced somatosensory and auditory stimulation. This work has been funded by the Novo Nordisk Foundation Interdisciplinary Synergy Program 2014 [“Biophysically adjusted state-informed cortex stimulation (BASICS); Grant No. NNF14OC0011413 ].