A threat to a virtual hand elicits motor cortex activation
We report an experiment where participants observed an attack on their virtual body as experienced in an immersive virtual reality (IVR) system. Participants sat by a table with their right hand resting upon it. In IVR, they saw a virtual table that was registered with the real one, and they had a virtual body that substituted their real body seen from a first person perspective. The virtual right hand was collocated with their real right hand. Event-related brain potentials were recorded in two conditions, one where the participant’s virtual hand was attacked with a knife and a control condition where the knife only struck the virtual table. Significantly greater P450 potentials were obtained in the attack condition confirming our expectations that participants had a strong illusion of the virtual hand being their own, which was also strongly supported by questionnaire responses. Higher levels of subjective virtual hand ownership correlated with larger P450 amplitudes. Mu-rhythm event-related desynchronization in the motor cortex and readiness potential (C3–C4) negativity were clearly observed when the virtual hand was threatened—as would be expected, if the real hand was threatened and the participant tried to avoid harm. Our results support the idea that event-related potentials may provide a promising non-subjective measure of virtual embodiment. They also support previous experiments on pain observation and are placed into context of similar experiments and studies of body perception and body ownership within cognitive neuroscience.
KeywordsBody ownership Rubber hand illusion Virtual reality Motor cortex Pain ERPs
This study was funded by the European Union FP7 Integrated Project VERE (No. 257695). MGF’s research was supported by the FI-DGR pre-doctorate grant from the Catalan government co-funded by the European Social Fund (EC-ESF). ARF has been supported by a research grant from the Spanish government (PSI2011-29219). The ERC project TRAVERSE (#227985) also contributed towards this research.
Supplementary material 1 (MPG 12188 kb)
- Babiloni C, Capotosto P, Brancucci A, Del Percio C, Petrini L, Buttiglione M, Cibelli G, Romani GL, Rossini PM, Arendt-Nielsen L (2008) Cortical alpha rhythms are related to the anticipation of sensorimotor interaction between painful stimuli and movements: a high-resolution EEG study. J Pain 9:902–911PubMedCrossRefGoogle Scholar
- Kalckert A, Ehrsson HH (2012) Moving a rubber hand that feels like your own: dissociation of ownership and agency. Front Hum Neurosci 6:40. doi: 10.3389/fnhum.2012.00040
- Kaplan D (2009) Structural equation modeling: foundations and extensions. Sage, Thousand Oaks, CAGoogle Scholar
- Maselli A, Slater M (2013) The building blocks of the full body ownership illusion. Front Hum Neurosci 7:83. doi: 10.3389/fnhum.2013.00083
- Petkova VI, Khoshnevis M, Ehrsson HH (2011) The perspective matters! Multisensory integration in ego-centric reference frames determines full-body ownership. Front Psychol 2:35. doi: 10.3389/fpsyg.2011.00035
- Slater M, Pérez Marcos D, Ehrsson H, Sanchez-Vives MV (2008) Towards a digital body: the virtual arm illusion. Front Hum Neurosci 2:6. doi: 10.3389/neuro.09.006.2008
- Steptoe W, Steed A, Slater M (2013) Human tails: ownership and control of extended humanoid avatars. IEEE Trans Vis Comput Graph 19(4):583–590Google Scholar
- Whitmarsh S, Nieuwenhuis ILC, Barendregt H, Jensen O (2011) Sensorimotor alpha activity is modulated in response to the observation of pain in others. Front Hum Neurosci 5:91. doi: 10.3389/fnhum.2011.00091