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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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tACS at Different Frequencies Modulates the Size of the Temporal Window of IllusionThe main plot shows the sigmoid fit (with aligned inflection points) of the average perceived illusion across participants (y axis) at different interbeep delays (x axis) in the three tACS conditions (Cz-Oz montage): tACS at IAF (black dots/curve), IAF+2 Hz (green dots/curve), and IAF−2 Hz (red dots/curve). Note that all the inflection points fall within the range of alpha frequency band, represented by the light-blue rectangle. Right inset shows the significant shifts of the average inflection points calculated for each participant sigmoid fit as a function of tACS condition. Error bars represent SEM. ∗p < 0.05; ∗∗p < 0.01; ∗∗∗p < 0.001.
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fig2: tACS at Different Frequencies Modulates the Size of the Temporal Window of IllusionThe main plot shows the sigmoid fit (with aligned inflection points) of the average perceived illusion across participants (y axis) at different interbeep delays (x axis) in the three tACS conditions (Cz-Oz montage): tACS at IAF (black dots/curve), IAF+2 Hz (green dots/curve), and IAF−2 Hz (red dots/curve). Note that all the inflection points fall within the range of alpha frequency band, represented by the light-blue rectangle. Right inset shows the significant shifts of the average inflection points calculated for each participant sigmoid fit as a function of tACS condition. Error bars represent SEM. ∗p < 0.05; ∗∗p < 0.01; ∗∗∗p < 0.001.

Mentions: In a second experiment, we sought causal evidence for a link between individual differences in IAF and the temporal window of the double-flash illusion. In 12 participants, we now delivered transcranial alternating current stimulation (tACS) over occipital cortex to modulate occipital oscillations [8] at their IAF or at slower (IAF−2 Hz) or faster (IAF+2 Hz) frequencies, i.e., far from IAF but still within the alpha band, while they were performing the flash-beep task (see Figure S2). If IAF causally determines the individual window of illusion (i.e., the inflection point of the sigmoid), then we hypothesized that driving IAF toward slower versus faster oscillations should result in wider versus shorter windows of illusion, respectively. Consistent with this hypothesis, repeated-measures ANOVA on inflection points (in ms) showed a main effect of tACS condition (F(2,22) = 10.11, p < 0.001, Figure 2). Post hoc paired t tests revealed that occipital tACS at IAF+2 Hz (92.7 ± 7.9 ms) significantly shrunk (t(11) = 1.82, p < 0.05, one-tailed), whereas IAF−2 Hz (106.4 ± 8.7 ms) significantly expanded (t(11) = 2.7, p = 0.01, one-tailed) the temporal window of the illusion relative to tACS at IAF (97.9 ± 7.6 ms) and relative to each other (t(11) = 4.29, p < 0.001, one-tailed). These tACS-dependent shifts in opposite directions suggest that IAF causally determines the temporal window of illusion.


Individual differences in alpha frequency drive crossmodal illusory perception.

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

tACS at Different Frequencies Modulates the Size of the Temporal Window of IllusionThe main plot shows the sigmoid fit (with aligned inflection points) of the average perceived illusion across participants (y axis) at different interbeep delays (x axis) in the three tACS conditions (Cz-Oz montage): tACS at IAF (black dots/curve), IAF+2 Hz (green dots/curve), and IAF−2 Hz (red dots/curve). Note that all the inflection points fall within the range of alpha frequency band, represented by the light-blue rectangle. Right inset shows the significant shifts of the average inflection points calculated for each participant sigmoid fit as a function of tACS condition. Error bars represent SEM. ∗p < 0.05; ∗∗p < 0.01; ∗∗∗p < 0.001.
© Copyright Policy - CC BY
Related In: Results  -  Collection

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

fig2: tACS at Different Frequencies Modulates the Size of the Temporal Window of IllusionThe main plot shows the sigmoid fit (with aligned inflection points) of the average perceived illusion across participants (y axis) at different interbeep delays (x axis) in the three tACS conditions (Cz-Oz montage): tACS at IAF (black dots/curve), IAF+2 Hz (green dots/curve), and IAF−2 Hz (red dots/curve). Note that all the inflection points fall within the range of alpha frequency band, represented by the light-blue rectangle. Right inset shows the significant shifts of the average inflection points calculated for each participant sigmoid fit as a function of tACS condition. Error bars represent SEM. ∗p < 0.05; ∗∗p < 0.01; ∗∗∗p < 0.001.
Mentions: In a second experiment, we sought causal evidence for a link between individual differences in IAF and the temporal window of the double-flash illusion. In 12 participants, we now delivered transcranial alternating current stimulation (tACS) over occipital cortex to modulate occipital oscillations [8] at their IAF or at slower (IAF−2 Hz) or faster (IAF+2 Hz) frequencies, i.e., far from IAF but still within the alpha band, while they were performing the flash-beep task (see Figure S2). If IAF causally determines the individual window of illusion (i.e., the inflection point of the sigmoid), then we hypothesized that driving IAF toward slower versus faster oscillations should result in wider versus shorter windows of illusion, respectively. Consistent with this hypothesis, repeated-measures ANOVA on inflection points (in ms) showed a main effect of tACS condition (F(2,22) = 10.11, p < 0.001, Figure 2). Post hoc paired t tests revealed that occipital tACS at IAF+2 Hz (92.7 ± 7.9 ms) significantly shrunk (t(11) = 1.82, p < 0.05, one-tailed), whereas IAF−2 Hz (106.4 ± 8.7 ms) significantly expanded (t(11) = 2.7, p = 0.01, one-tailed) the temporal window of the illusion relative to tACS at IAF (97.9 ± 7.6 ms) and relative to each other (t(11) = 4.29, p < 0.001, one-tailed). These tACS-dependent shifts in opposite directions suggest that IAF causally determines the temporal window of illusion.

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