Figure 3.

Neural activity in IPS and PMC in relation to tactile stimulation during the RHI. To examine the temporal profiles of the illusion-related high-γ activity observed in the IPS and PMC (Fig. 2) in relation to the applied tactile stimulation, we segmented the ECoG data into “during touch” (DT; 700-ms data window) and “between touches” periods (BT; 1300-ms data window) and compared the mean high-γ power across the 2 period types (DT, BT), cortical areas (IPS, PMC), and visuotactile synchrony (SynchPOST, AsynchPOST). To examine the hypothesis that illusion-related activity in the IPS is more time-locked to the tactile stimulation than the PMC, the analysis-of-interest was the 3-way interaction between area × period type × synchrony. Because it typically takes peripheral tactile stimulation about 200 ms to activate neurons in multisensory areas (Duhamel et al. 1998), we shifted DT and BT data windows in the ECoG signal 200 ms forward in time relative the peripheral touch sensor. The results showed that a 200 ms shift of the “touch data window” yielded a significant 3-way interaction (B), which was not the case without a shift (A). Analyzing the 3-way interaction term over continuous shifts in the “touch data window” revealed that the illusion-related IPS activity was significantly more modulated by the tactile stimulus than PMC for shifts between 130 and 300 ms (C), which is in accordance with temporal response properties of IPS neurons to tactile stimulation (Duhamel et al. 1998). We speculate that this pattern of results may reflect different functional roles of these 2 key areas in the limb self-attribution process, in which the IPS is more involved in the self-attribution of sensory signals that originate from the “owned” rubber hand, while the PMC—as the hierarchically highest level of multisensory body representation that is targeted by the RHI—is primarily involved in generating the continuous feeling of ownership. *DT = During touch; BT = Between touches.