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Individual differences in alpha frequency drive crossmodal illusory perception.

Cecere R, Rees G, Romei V - Curr. Biol. (2014)

Bottom Line: Moreover, presenting a brief tone can phase-reset such oscillations in visual cortex.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).

View Article: PubMed Central - PubMed

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.

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Individual Alpha Frequency Correlates with the Temporal Profile of the Double-Flash Illusion(A) Across-participants average probability of perceiving the illusion plotted as a function of interbeep delay. The red curve represents the sigmoid fit determining the amplitude of the window of illusion, corresponding to the inflection point of the sigmoid.(B) Across-participants average brain topography of oscillatory alpha activity during task performance and corresponding average FFT showing the peak frequency in the alpha band (light blue rectangle).(C) Scalp topography of the correlation index (Pearson’s R) between individual inflection points and alpha peak frequency (IAF) at each electrode, showing maximal correlation (r = 0.697; p < 0.001) around occipital electrodes (O1, O2, Oz). Scatterplot of the significant correlation between each individual’s inflection points (y axis) and the duration of one occipital alpha cycle (i.e., IAF; x axis).
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fig1: Individual Alpha Frequency Correlates with the Temporal Profile of the Double-Flash Illusion(A) Across-participants average probability of perceiving the illusion plotted as a function of interbeep delay. The red curve represents the sigmoid fit determining the amplitude of the window of illusion, corresponding to the inflection point of the sigmoid.(B) Across-participants average brain topography of oscillatory alpha activity during task performance and corresponding average FFT showing the peak frequency in the alpha band (light blue rectangle).(C) Scalp topography of the correlation index (Pearson’s R) between individual inflection points and alpha peak frequency (IAF) at each electrode, showing maximal correlation (r = 0.697; p < 0.001) around occipital electrodes (O1, O2, Oz). Scatterplot of the significant correlation between each individual’s inflection points (y axis) and the duration of one occipital alpha cycle (i.e., IAF; x axis).

Mentions: To assess the correlation between individual alpha frequency (IAF) peak and the width of the temporal window of integration in which the illusion is perceived, we tested 22 healthy volunteers using a paradigm adapted from Shams et al. [4] where two beeps (7 ms duration) were played at different time delays between 36–204 ms (12 ms steps; see Supplemental Information and Figure S1 available online). A white disk was flashed for 12 ms below a fixation point time-aligned to the first beep, and participants reported whether they perceived one or two flashes. A sigmoid function was fitted to individual observations (see behavioral data analysis in Supplemental Information) to determine the inflection point of each participant’s behavioral curve, providing a reliable estimate of the temporal window in which the illusion was maximally perceived (average ∼100 ms; Figure 1A). EEG activity was recorded during the task and fast Fourier transform (FFT) used to calculate individual alpha frequency (IAF) peaks across the entire electrode array (Figure 1B). Inflection point values were then correlated with the width of IAF cycles revealing that these two measures were strongly and positively correlated with maxima over occipital electrodes (O1, O2, and Oz; n = 22, r = 0.697, regression slope = 1.4, y intercept = 0.34, p < 0.001; see Figure 1C), in line with our hypothesis.


Individual differences in alpha frequency drive crossmodal illusory perception.

Cecere R, Rees G, Romei V - Curr. Biol. (2014)

Individual Alpha Frequency Correlates with the Temporal Profile of the Double-Flash Illusion(A) Across-participants average probability of perceiving the illusion plotted as a function of interbeep delay. The red curve represents the sigmoid fit determining the amplitude of the window of illusion, corresponding to the inflection point of the sigmoid.(B) Across-participants average brain topography of oscillatory alpha activity during task performance and corresponding average FFT showing the peak frequency in the alpha band (light blue rectangle).(C) Scalp topography of the correlation index (Pearson’s R) between individual inflection points and alpha peak frequency (IAF) at each electrode, showing maximal correlation (r = 0.697; p < 0.001) around occipital electrodes (O1, O2, Oz). Scatterplot of the significant correlation between each individual’s inflection points (y axis) and the duration of one occipital alpha cycle (i.e., IAF; x axis).
© Copyright Policy - CC BY
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4300399&req=5

fig1: Individual Alpha Frequency Correlates with the Temporal Profile of the Double-Flash Illusion(A) Across-participants average probability of perceiving the illusion plotted as a function of interbeep delay. The red curve represents the sigmoid fit determining the amplitude of the window of illusion, corresponding to the inflection point of the sigmoid.(B) Across-participants average brain topography of oscillatory alpha activity during task performance and corresponding average FFT showing the peak frequency in the alpha band (light blue rectangle).(C) Scalp topography of the correlation index (Pearson’s R) between individual inflection points and alpha peak frequency (IAF) at each electrode, showing maximal correlation (r = 0.697; p < 0.001) around occipital electrodes (O1, O2, Oz). Scatterplot of the significant correlation between each individual’s inflection points (y axis) and the duration of one occipital alpha cycle (i.e., IAF; x axis).
Mentions: To assess the correlation between individual alpha frequency (IAF) peak and the width of the temporal window of integration in which the illusion is perceived, we tested 22 healthy volunteers using a paradigm adapted from Shams et al. [4] where two beeps (7 ms duration) were played at different time delays between 36–204 ms (12 ms steps; see Supplemental Information and Figure S1 available online). A white disk was flashed for 12 ms below a fixation point time-aligned to the first beep, and participants reported whether they perceived one or two flashes. A sigmoid function was fitted to individual observations (see behavioral data analysis in Supplemental Information) to determine the inflection point of each participant’s behavioral curve, providing a reliable estimate of the temporal window in which the illusion was maximally perceived (average ∼100 ms; Figure 1A). EEG activity was recorded during the task and fast Fourier transform (FFT) used to calculate individual alpha frequency (IAF) peaks across the entire electrode array (Figure 1B). Inflection point values were then correlated with the width of IAF cycles revealing that these two measures were strongly and positively correlated with maxima over occipital electrodes (O1, O2, and Oz; n = 22, r = 0.697, regression slope = 1.4, y intercept = 0.34, p < 0.001; see Figure 1C), in line with our hypothesis.

Bottom Line: Moreover, presenting a brief tone can phase-reset such oscillations in visual cortex.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).

View Article: PubMed Central - PubMed

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
Related in: MedlinePlus