Individual differences in alpha frequency drive crossmodal illusory perception.
Bottom Line: Stimulus temporal proximity critically determines whether or not these inputs are bound together.Based on these observations, we hypothesized that the duration of each alpha cycle might provide the temporal unit to bind audio-visual events.Participants then performed the same task while receiving occipital transcranial alternating current stimulation (tACS), to modulate oscillatory activity either at their IAF or at off-peak alpha frequencies (IAF±2 Hz).
Affiliation: Centre for Brain Science, Department of Psychology, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK; Institute of Neuroscience and Psychology, University of Glasgow, 58 Hillhead Street, Glasgow G12 8QB, UK.Show MeSH
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Mentions: If the occurrence of the illusion is predicted by the alpha oscillatory amplitude on a trial-by-trial basis , then the proneness to the illusion across participants in the present study may be similarly indexed by the individual amount of alpha power over occipital areas. Here, back to experiment 1, we differently analyzed our data and further tested this hypothesis by assessing the relationship between the proneness to the illusion (calculated as the overall probability of perceiving the illusion across the 15 temporal delays) and how this relates to another index of alpha oscillations, namely, its power. In line with the findings of Lange and colleagues , we found that higher levels of alpha power were inversely correlated with the proneness to perceive the illusion (r = 0.52, p < 0.015, see Figure 4). Intriguingly, in light of the existing literature these new findings predict that alpha power  and gray matter volume in early visual cortices  may be tightly linked, a hypothesis that needs direct empirical support. Moreover, this represents an important confirmation that adds to previous literature on the role of alpha power as a momentary index of cortical excitability [16, 22, 23] and alpha coherence between auditory and visual cortices as recently reported by Keil and colleagues .
Affiliation: Centre for Brain Science, Department of Psychology, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK; Institute of Neuroscience and Psychology, University of Glasgow, 58 Hillhead Street, Glasgow G12 8QB, UK.