Abstract
In the rubber hand illusion (RHI), the subject recognizes a fake hand as his or her own. We recently found that the observation of embodied fake hand movement elicited mu-rhythm (8–13 Hz) desynchronization on electroencephalography (EEG), suggesting brain activation in the sensorimotor regions. However, it is known that mu-rhythm desynchronization during action observation is confounded with occipital alpha-rhythm desynchronization, which is modulated by attention. This study examined the independence of brain activities in the sensorimotor and occipital regions relating to the movement observation under the RHI. The invisible participant’s left and fake right hands were stroked simultaneously, which was interrupted by unexpected fake hand movements. A mirror-reversed image of the fake hand was shown on a monitor in front of the participant with a delay of 80, 280, or 480 ms. Illusion strength decreased as a function of the delay. EEG independent component analysis (ICA) and ICA clustering revealed six clusters with observation-induced desynchronization of 8–13 Hz frequency band. In the right sensorimotor cluster, mu-rhythm desynchronization was the greatest under the 80-ms delay, while alpha-rhythm desynchronization of the occipital clusters did not show delay-dependence. These results suggest that brain activation in the sensorimotor areas (i.e., mu-rhythm desynchronization) induced by embodied fake hand movement is independent of that in the occipital areas (alpha-rhythm desynchronization).
Highlights
Sense of body ownership describes the subjective feeling that one’s body belongs to oneself and is a fundamental aspect of one’s sense of self (Gallagher, 2000, 2005)
Proprioceptive drift was significantly influenced by visual feedback delay (F(2,64) = 17.7, η2 = 0.36, p < 0.01; oneway ANOVA; Figure 2E)
We examined the effects of delayed visual feedback on illusory ownership of a fake hand and EEG mu- and alpha-rhythm desynchronization elicited by fake hand movement
Summary
Sense of body ownership describes the subjective feeling that one’s body belongs to oneself and is a fundamental aspect of one’s sense of self (Gallagher, 2000, 2005). In a related EEG study, Perry and Bentin (2010) suggested that desynchronization at ∼10 Hz induced by action observation depended on attentional demand because EEG power reduction at central (C3 and C4 of the international 10–20 system; mu-rhythm) and occipital electrodes (O1 and O2; alpha-rhythm) showed similar patterns and were modulated by task difficulty. The current study investigated the dependence/independence of brain activities in the sensorimotor areas (i.e., mu-rhythm desynchronization) related to the movement observation under the RHI and those in the occipital areas (alpha-rhythm desynchronization) reflecting attention. We introduced three visual feedback delays during the illusion induction (i.e., 80, 280, or 480 ms), which might induce different effects on attention and the RHI, compared to the synchronous/asynchronous stimulation in our previous study. We predicted that the sensorimotor mu-rhythm and the occipital alpha-rhythm component were modulated differently depending on the feedback delay
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