Abstract
In a previous study, we reported that when spatial window of a Gabor moved constantly whereas the carrier grating stayed still or drifted in the opposite direction, the whole stimulus appeared to move only intermittently with a constant temporal rate of 4-6 Hz regardless of the speed of stimuli (Nakayama et al., VSS 2014). We interpreted that this illusory saltation is essentially a consequence of periodical resets of an increasing discrepancy in the spatial position signals between luminance-defined grating motion and contrast-defined window, but that the apparent rhythm of saltation is determined by a neural mechanism that updates the perceptual awareness at a fixed temporal rate of 4-6 Hz. Similar temporal fragmentation of perception at 4-6 Hz has been reported among motion-blind patients (Hess et al., 1989), implying that this rhythm is related with the temporal continuity of perceptual awareness. To investigate the neural basis of this illusory discrete perception, we here examined EEG signals during the observation of illusion. The analyses revealed that theta-band power was significantly attenuated focusing around parietal-occipital regions when participants observed stimuli that caused illusory discrete motion as compared to when they observed smoothly moving stimuli. We suggest that these parietal theta components may reflect a clock-like mechanism which underlies the temporal continuity of conscious perception.
Meeting abstract presented at VSS 2016