Abstract
We investigated whether the inferior parietal lobule (IPL) responds in real-time to multisensory inconsistency during movement. The IPL is thought to be involved in both the detection of inconsistencies in multisensory information obtained during movement and that obtained during self-other discrimination. However, because of the limited temporal resolution of conventional neuroimaging techniques, it is difficult to distinguish IPL activity during movement from that during self-other discrimination. We simultaneously conducted electroencephalography (EEG) and near-infrared spectroscopy (NIRS) with the goal of examining IPL activity with a high spatiotemporal resolution during single reaching movements. Under a visual feedback-delay condition, gamma event-related synchronization (γ-ERS), i.e., an increase in gamma (31–47 Hz) EEG power occurred during reaching movements. This γ-ERS is considered to reflect processing of information about prediction errors. To integrate this temporal information with spatial information from the NIRS signals, we developed a new analysis technique that enabled estimation of the regions that show a hemodynamic response characterized by EEG fluctuation present in the visual feedback-delay condition. As a result, IPL activity was explained by γ-ERS specific to visual feedback delay during movements. Thus, we succeeded in demonstrating real-time activation of the IPL in response to multisensory inconsistency. However, we did not find any correlation between either IPL activity or γ-ERS with the sense of agency. Therefore, our results suggest that while the IPL is influenced by prediction error signals, it does not engage in direct processing underlying the conscious experience of making a movement, which is the foundation of self-other discrimination.
Highlights
When watching a moving hand, we are able to determine whether the hand is our own or belongs to someone else based on the consistency between the action and our proprioceptive sensation
Reaching movements in the Delay condition took more time to perform (Delay: 1028.5 ± 115.0 ms; Non-Delay: 867.4 ± 84.6 ms; t(13) = 4.48, p < 0.001), while maximum velocity (Delay: 566.1 ± 57.4 mm/s; Non-Delay: 613.1 ± 65.2 mm/s; t(13) = −1.60, p = 0.13) and response time (Delay: 408.8 ± 1.5 ms; Non-Delay: 400.5 ± 1.4 ms; t(13) = 2.03, p = 0.063) did not differ between conditions. These results indicate that the change in performance was caused by the delay in visual feedback and that it was not a consequence of a speed-accuracy tradeoff
We investigated whether the inferior parietal lobule (IPL) responds to multisensory inconsistencies online during reaching movements by simultaneously recording EEG-nearinfrared spectroscopy (NIRS) signals during a visual feedback-delay task
Summary
When watching a moving hand, we are able to determine whether the hand is our own or belongs to someone else based on the consistency between the action and our proprioceptive sensation. Previous neuroimaging studies of healthy participants have indicated that IPL activation increases ( in the right hemisphere) in response to temporal or spatial errors in visual feedback about movements (Farrer and Frith, 2002; Farrer et al, 2003, 2008; Shimada et al, 2005; Balslev et al, 2006). Based on these findings, researchers have proposed that the right IPL is involved in attributing actions to others based on multisensory inconsistencies. The low temporal resolution of the imaging techniques used in previous studies has prevented the separation of brain activity related to the real-time feeling of control from that related to conscious judgment of agency
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