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Luca Ronconi, David Melcher; Alpha oscillation phase determines the timing of perception: evidence from sensory entrainment. Journal of Vision 2017;17(10):726. doi: https://doi.org/10.1167/17.10.726.
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Introduction: While sensory inputs are continuous, perception involves grouping information over time. Recent studies have renewed the idea that the processing of information within different temporal windows is linked to the phase and/or frequency of ongoing oscillatory activity in the alpha band (8-12 Hz). However, being correlational in nature, this evidence might merely reflect a non-functional by-product rather than a causal mechanism. A causal link can be shown with methods that manipulate oscillatory activity, exploiting the tendency of neural oscillations to show entrainment to periodic external forces. Methods: Here, we used audio-visual entrainment at the lower and upper boundaries of the alpha band (i.e. audio-visual rhythmic sequences running at 8.5 vs. 11.5 Hz) in the pre-stimulus period of a temporal integration/segregation task. We hypothesized that entrainment would align ongoing alpha oscillations and drive them towards either a slower or faster frequency. To measure any oscillation in temporal perception as a consequence of the entrainment, we employed a dense-sampling method. We measured the perceptual interpretation of a bistable stimulus, consisting of two brief flashes separated by a brief blank delay that was perceived as either one single flash or two flashes. We densely sampled performance at different time points after the offset of the entrainment, in order to measure any fluctuations in the interpretation of the stimulus. Results: We found a significant phase alignment of the perceptual oscillation across subjects for both entrainment frequencies (8.5 and 11.5 Hz). The two different conditions yielded power spectrums that each peaked near the entrainment frequency, which was confirmed also by a significant fit of a sinusoid to the behavioral oscillation in each condition. Conclusion: This pattern of results provides evidence that the phase of the ongoing neural oscillations is causally linked to the temporal organization of perception.
Meeting abstract presented at VSS 2017
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