Alpha band oscillations correlate with illusory self-location induced by virtual reality Bigna Lenggenhager, 1, * Pa ¨r Halje 1, * and Olaf Blanke 1,2 1 Laboratory of Cognitive Neuroscience, Federal Institute of Technology, Lausanne, Switzerland 2 Department of Neurology, University Hospital, Geneva, Switzerland Keywords: frequency analysis, medial prefrontal cortex, multisensory integration, mu-rhythm, peripersonal space Abstract Neuroscience of the self has focused on high-level mechanisms related to language, memory or imagery of the self. However, recent evidence suggests that low-level mechanisms such as multisensory and sensorimotor integration may play a fundamental role in self- related processing. Here we used virtual reality technology and visuo-tactile conflict to study such low-level mechanisms and manipulate where participants experienced their self to be localized (self-location). Frequency analysis and electrical neuroimaging of co-recorded high-resolution electroencephalography revealed body-specific alpha band power modulations in bilateral sensorimotor cortices. Furthermore, alpha power in the medial prefrontal cortex (mPFC) was correlated with the degree of experimentally manipulated self-location. We argue that these alpha oscillations in sensorimotor cortex and mPFC reflect self-location as manipulated through multisensory conflict. Introduction Neuroscientific and philosophical theories stress the importance of bodily processes in self-consciousness (Berlucchi & Aglioti, 1997; Gallagher, 2005; Metzinger, 2007). Experimentation with bodily stimuli is complex as bodily inputs are continuously present and are characterized by information from the motor system as well as many different senses, including tactile, proprioceptive, nociceptive and vestibular (for a review, see e.g. Lackner & DiZio, 2000). Recent behavioural work (Ehrsson, 2007; Lenggenhager et al., 2007; Petkova & Ehrsson, 2008; Aspell et al., 2009; Lenggenhager et al., 2009) has developed experimental techniques to manipulate and study bodily self-consciousness by providing ambiguous multisensory information about the location and appearance of one’s own body using video- based technology. Following one line of such research, synchronous stroking of the participants back with a seen body in front of them (Lenggenhager et al., 2007) led to changes in global aspects of self- consciousness, such as self-location or self-identification with a body (Blanke & Metzinger, 2009). What brain mechanisms are underlying these changes? Studies in patients with abnormal bodily self- consciousness pointed to a disturbance of multisensory processes, in particular in the temporo-parietal cortex (Blanke et al., 2002, 2004; De Ridder et al., 2007), but also in the frontal and parietal cortices (Heydrich et al., 2011; Lopez et al., 2010). Here we further developed our previous research protocol to manipulate self-location (Lenggenhager et al., 2007) by using virtual reality (VR) technology, optical tracking, real-time projection (on a large-size screen) and the measurement of the associated brain activity [high-resolution electroencephalography (EEG)]. We analysed changes in the alpha (8–13 Hz) and gamma (30–50 Hz and 30– 100 Hz) bands because of their association with multisensory integration and self-related processing. Alpha band power over the sensorimotor cortex has been linked to the perception of human bodies and the mirror neuron system, and is an index of motor (Pineda, 2005) and somatosensory (Pfurtscheller, 1981) activities. It has for example been linked to the degree of identification with the observed actor or action (Oberman et al., 2005), and to human touch viewed from egocentric vs allocentric perspectives (Cheyne et al., 2003). Accord- ingly, we predicted that alpha band power over (pre-)motor and ⁄ or somatosensory areas would also reflect changes in bodily self- consciousness (self-identification and self-location). This is in line with previous findings that linked the related rubber hand illusion to premotor and parietal cortices (Ehrsson et al., 2004). We thus expected to find body-specific alpha ⁄ mu band suppression depending on the synchrony of stroking. Gamma oscillations have previously been linked to integration across different sensory modalities into a coherent percept (Senkow- ski et al., 2007). Neuronal systems involved in these processes are likely to be engaged during the manipulation of self-location through visuo-tactile conflict. In accordance with this idea, an increased power in the lower gamma band (30–50 Hz) over parietal scalp regions was found during the integration of tactile and visual cues in peripersonal space in a rubber hand illusion-like paradigm (Kanay- ama et al., 2007, 2009). We therefore hypothesized body-specific Correspondence: Dr B. Lenggenhager, Social and Cognitive Neuroscience Laboratory, Psychology Department of ‘Sapienza’, Via dei Marsi 78, 00185 Rome, Italy. E-mail: bigna.lenggenhager@gmail.com *B.L. and P.H. contributed equally to this study. Received 4 November 2010, revised 12 January 2011, accepted 7 February 2011 European Journal of Neuroscience, pp. 1–9, 2011 doi:10.1111/j.1460-9568.2011.07647.x ª 2011 The Authors. European Journal of Neuroscience ª 2011 Federation of European Neuroscience Societies and Blackwell Publishing Ltd European Journal of Neuroscience