Modulation of Illusory Reversal in Tactile Temporal Order by the Phase of Posterior α Rhythm.

The subjective temporal order of tactile stimuli, delivered sequentially to each hand with an interval of 100-300 ms, is often inverted when the arms are crossed. Based on data from behavioral and neuroimaging studies, it has been proposed that the reversal is due to a conflict between anatomical and spatial representations of the tactile signal or to the production of an inverted apparent motion signal. Because the α rhythms, which consist of a few distinct components, reportedly modulate tactile perception and apparent motion and serve as a 10 Hz timer, we hypothesized that the illusory reversal would be regulated by some of the α rhythms. To test this hypothesis, we conducted magnetoencephalographic recordings in both male and female participants during the tactile temporal order judgment task. We decomposed the α rhythms into five independent components and discovered that the illusory reversal was modulated by the phase of one independent component with strong current sources near the parieto-occipital (PO) sulcus (peri-PO component). As expected, the estimated current sources distributed over the human MST implicated to represent tactile apparent motion, in addition to the intraparietal region implicated in mapping tactile signals in space. However, the strongest source was located in the precuneus that occupies a central hub region in the cortical networks and receives tactile inputs through a tecto-thalamic pathway. These results suggest that the peri-PO component plays an essential role in regulating tactile temporal perception by modulating the thalamic nuclei that interconnect the superior colliculus with the cortical networks. Despite a long-held hypothesis that the posterior α rhythm serves as a 10 Hz timer that regulates human temporal perception, the contribution of the α rhythms in temporal perception is still unclear. We examined how the α rhythms influence tactile temporal order judgment. Judgment reversal depended on the phase of one particular α rhythm with its source near the parieto-occipital sulcus. The peri-parieto-occipital α rhythm may play a crucial role in organizing tactile temporal perception.