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Sounds reset rhythms of visual cortex and corresponding human visual perception.

Romei V, Gross J, Thut G - Curr. Biol. (2012)

Bottom Line: In principle, this may result in stimulus-locked periodicity in behavioral performance.Here we considered this possible cross-modal impact of a sound for one of the best-characterized rhythms arising from the visual system, namely occipital alpha-oscillations (8-14 Hz).This shows that cross-modal phase locking of oscillatory visual cortex activity can arise in the human brain to affect perceptual and EEG measures of visual processing in a cyclical manner, consistent with occipital alpha oscillations underlying a rapid cycling of neural excitability in visual areas.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neuroscience and Psychology, University of Glasgow, 58 Hillhead Street, Glasgow G12 8QB, UK. v.romei@ucl.ac.uk

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Alpha Phase Locking for No-TMS Trials in Experiment 2(A) Instantaneous EEG phase, time locked to sound onset, was computed with the Hilbert transform after applying a band-pass filter (8–14 Hz). Right panel shows the 10 Hz phase-locking topography, with the effect evident in sensors overlaying not only auditory but also highlighted parieto-occipital cortex. Left panel depicts 10 Hz phase-locking for highlighted parieto-occipital sensors, which was significant (p < 0.001) between 50 ms and 250 ms following auditory stimulus onset (shaded window).(B) Preferred alpha phase at 100 ms delay. Circular statistics were used to estimate PH(100), the mean instantaneous phase at 100 ms post sound (the time of highest sound-induced enhancement of phosphene detection rate in experiment 1). The number of trials within ±10 degrees of PH(100) is shown at left against time since sound, with corresponding topography at right. Note that the fluctuation in number of trials showing preferred phase PH(100) peaks not only at 100 ms (by definition), but also at around ∼200 ms, with the resulting cyclical pattern closely resembling the periodicity of perceived phosphene rate shown in Figure 1, in terms of peak-to-peak interval and peak latencies (i.e., frequency and phase). The shaded windows highlight that PH(100) not only at 100 ms (±20 m) but also at 200 ms (±20) was significantly higher than baseline (BSL) or the 150 delay (±20ms), all ∗p < 0.05 Bonferroni corrected.(C) EEG-phosphene correlation for separate datasets from experiments 1 and 2 (same participants). Scatterplot with red points and red line shows that the number of no-TMS EEG trials showing a phase within PH(100) at 19 equally spaced time points in the window 30 ms to 300 ms (experiment 2) correlates with the corresponding phosphene rates (scored along right axis) from separate experiment 1 (Figure 1). Please note the baseline (no-sound) condition was not considered in this analysis, as a time window relative to sound onset cannot be set for the preferred-phase EEG measure without a sound. Scatterplot with black points and black line shows a similar correlation between phosphene perception rate on the TMS trials in experiment 2 (scored along left axis) and dynamics of preferred phase for no-TMS trials in the same experiment.
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fig2: Alpha Phase Locking for No-TMS Trials in Experiment 2(A) Instantaneous EEG phase, time locked to sound onset, was computed with the Hilbert transform after applying a band-pass filter (8–14 Hz). Right panel shows the 10 Hz phase-locking topography, with the effect evident in sensors overlaying not only auditory but also highlighted parieto-occipital cortex. Left panel depicts 10 Hz phase-locking for highlighted parieto-occipital sensors, which was significant (p < 0.001) between 50 ms and 250 ms following auditory stimulus onset (shaded window).(B) Preferred alpha phase at 100 ms delay. Circular statistics were used to estimate PH(100), the mean instantaneous phase at 100 ms post sound (the time of highest sound-induced enhancement of phosphene detection rate in experiment 1). The number of trials within ±10 degrees of PH(100) is shown at left against time since sound, with corresponding topography at right. Note that the fluctuation in number of trials showing preferred phase PH(100) peaks not only at 100 ms (by definition), but also at around ∼200 ms, with the resulting cyclical pattern closely resembling the periodicity of perceived phosphene rate shown in Figure 1, in terms of peak-to-peak interval and peak latencies (i.e., frequency and phase). The shaded windows highlight that PH(100) not only at 100 ms (±20 m) but also at 200 ms (±20) was significantly higher than baseline (BSL) or the 150 delay (±20ms), all ∗p < 0.05 Bonferroni corrected.(C) EEG-phosphene correlation for separate datasets from experiments 1 and 2 (same participants). Scatterplot with red points and red line shows that the number of no-TMS EEG trials showing a phase within PH(100) at 19 equally spaced time points in the window 30 ms to 300 ms (experiment 2) correlates with the corresponding phosphene rates (scored along right axis) from separate experiment 1 (Figure 1). Please note the baseline (no-sound) condition was not considered in this analysis, as a time window relative to sound onset cannot be set for the preferred-phase EEG measure without a sound. Scatterplot with black points and black line shows a similar correlation between phosphene perception rate on the TMS trials in experiment 2 (scored along left axis) and dynamics of preferred phase for no-TMS trials in the same experiment.

Mentions: In experiment 2, we acquired concurrent EEG in the same paradigm and the same participants as in experiment 1, but with fewer TMS time points (now 7 rather than 19, see Experimental Procedures) to allow more trials in each condition for EEG analysis and a higher proportion (1/8) of no-TMS trials. Phosphene perception rates were highly correlated between experiments 1 and 2 (r(7) = 0.90; p < 0.003), for the sound-TMS relations that were in common between these two studies, i.e., experiment 2 essentially reproduced the ∼10 Hz cyclical pattern of phosphene perception of experiment 1 (see below for more detailed analysis of this pattern). We next analyzed EEG data from experiment 2, initially for sound-only trials (no TMS) because these can provide a pure measure of phase locking of EEG activity to the critical sound in the absence of TMS (thus without any associated visual percept). Significant 10 Hz phase locking (p < 0.001) to the critical sound was evident not only for sensors overlaying auditory cortex but also over parieto-occipital cortex, from 50 ms to 250 ms following auditory stimulus onset (Figure 2A). Note that none of the frontal electrodes showed significant phase locking. We then calculated the number of trials showing a phase for parieto-occipital electrodes within ±10 degrees of the preferred phase at 100 ms (the time point postsound at which phosphene rate peaked in experiment 1). This measure showed a cyclical pattern, being significantly higher not only around 100 ms (by definition) but also around 200 ms after the sound, as compared to the 150 ms delay or the no-sound baseline (all p < 0.05, Bonferroni corrected); see Figure 2B. This pattern is strikingly reminiscent of the phosphene rate data from the previous experiment (Figure 1) and the correlated phosphene perception rate of the new experiment.


Sounds reset rhythms of visual cortex and corresponding human visual perception.

Romei V, Gross J, Thut G - Curr. Biol. (2012)

Alpha Phase Locking for No-TMS Trials in Experiment 2(A) Instantaneous EEG phase, time locked to sound onset, was computed with the Hilbert transform after applying a band-pass filter (8–14 Hz). Right panel shows the 10 Hz phase-locking topography, with the effect evident in sensors overlaying not only auditory but also highlighted parieto-occipital cortex. Left panel depicts 10 Hz phase-locking for highlighted parieto-occipital sensors, which was significant (p < 0.001) between 50 ms and 250 ms following auditory stimulus onset (shaded window).(B) Preferred alpha phase at 100 ms delay. Circular statistics were used to estimate PH(100), the mean instantaneous phase at 100 ms post sound (the time of highest sound-induced enhancement of phosphene detection rate in experiment 1). The number of trials within ±10 degrees of PH(100) is shown at left against time since sound, with corresponding topography at right. Note that the fluctuation in number of trials showing preferred phase PH(100) peaks not only at 100 ms (by definition), but also at around ∼200 ms, with the resulting cyclical pattern closely resembling the periodicity of perceived phosphene rate shown in Figure 1, in terms of peak-to-peak interval and peak latencies (i.e., frequency and phase). The shaded windows highlight that PH(100) not only at 100 ms (±20 m) but also at 200 ms (±20) was significantly higher than baseline (BSL) or the 150 delay (±20ms), all ∗p < 0.05 Bonferroni corrected.(C) EEG-phosphene correlation for separate datasets from experiments 1 and 2 (same participants). Scatterplot with red points and red line shows that the number of no-TMS EEG trials showing a phase within PH(100) at 19 equally spaced time points in the window 30 ms to 300 ms (experiment 2) correlates with the corresponding phosphene rates (scored along right axis) from separate experiment 1 (Figure 1). Please note the baseline (no-sound) condition was not considered in this analysis, as a time window relative to sound onset cannot be set for the preferred-phase EEG measure without a sound. Scatterplot with black points and black line shows a similar correlation between phosphene perception rate on the TMS trials in experiment 2 (scored along left axis) and dynamics of preferred phase for no-TMS trials in the same experiment.
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fig2: Alpha Phase Locking for No-TMS Trials in Experiment 2(A) Instantaneous EEG phase, time locked to sound onset, was computed with the Hilbert transform after applying a band-pass filter (8–14 Hz). Right panel shows the 10 Hz phase-locking topography, with the effect evident in sensors overlaying not only auditory but also highlighted parieto-occipital cortex. Left panel depicts 10 Hz phase-locking for highlighted parieto-occipital sensors, which was significant (p < 0.001) between 50 ms and 250 ms following auditory stimulus onset (shaded window).(B) Preferred alpha phase at 100 ms delay. Circular statistics were used to estimate PH(100), the mean instantaneous phase at 100 ms post sound (the time of highest sound-induced enhancement of phosphene detection rate in experiment 1). The number of trials within ±10 degrees of PH(100) is shown at left against time since sound, with corresponding topography at right. Note that the fluctuation in number of trials showing preferred phase PH(100) peaks not only at 100 ms (by definition), but also at around ∼200 ms, with the resulting cyclical pattern closely resembling the periodicity of perceived phosphene rate shown in Figure 1, in terms of peak-to-peak interval and peak latencies (i.e., frequency and phase). The shaded windows highlight that PH(100) not only at 100 ms (±20 m) but also at 200 ms (±20) was significantly higher than baseline (BSL) or the 150 delay (±20ms), all ∗p < 0.05 Bonferroni corrected.(C) EEG-phosphene correlation for separate datasets from experiments 1 and 2 (same participants). Scatterplot with red points and red line shows that the number of no-TMS EEG trials showing a phase within PH(100) at 19 equally spaced time points in the window 30 ms to 300 ms (experiment 2) correlates with the corresponding phosphene rates (scored along right axis) from separate experiment 1 (Figure 1). Please note the baseline (no-sound) condition was not considered in this analysis, as a time window relative to sound onset cannot be set for the preferred-phase EEG measure without a sound. Scatterplot with black points and black line shows a similar correlation between phosphene perception rate on the TMS trials in experiment 2 (scored along left axis) and dynamics of preferred phase for no-TMS trials in the same experiment.
Mentions: In experiment 2, we acquired concurrent EEG in the same paradigm and the same participants as in experiment 1, but with fewer TMS time points (now 7 rather than 19, see Experimental Procedures) to allow more trials in each condition for EEG analysis and a higher proportion (1/8) of no-TMS trials. Phosphene perception rates were highly correlated between experiments 1 and 2 (r(7) = 0.90; p < 0.003), for the sound-TMS relations that were in common between these two studies, i.e., experiment 2 essentially reproduced the ∼10 Hz cyclical pattern of phosphene perception of experiment 1 (see below for more detailed analysis of this pattern). We next analyzed EEG data from experiment 2, initially for sound-only trials (no TMS) because these can provide a pure measure of phase locking of EEG activity to the critical sound in the absence of TMS (thus without any associated visual percept). Significant 10 Hz phase locking (p < 0.001) to the critical sound was evident not only for sensors overlaying auditory cortex but also over parieto-occipital cortex, from 50 ms to 250 ms following auditory stimulus onset (Figure 2A). Note that none of the frontal electrodes showed significant phase locking. We then calculated the number of trials showing a phase for parieto-occipital electrodes within ±10 degrees of the preferred phase at 100 ms (the time point postsound at which phosphene rate peaked in experiment 1). This measure showed a cyclical pattern, being significantly higher not only around 100 ms (by definition) but also around 200 ms after the sound, as compared to the 150 ms delay or the no-sound baseline (all p < 0.05, Bonferroni corrected); see Figure 2B. This pattern is strikingly reminiscent of the phosphene rate data from the previous experiment (Figure 1) and the correlated phosphene perception rate of the new experiment.

Bottom Line: In principle, this may result in stimulus-locked periodicity in behavioral performance.Here we considered this possible cross-modal impact of a sound for one of the best-characterized rhythms arising from the visual system, namely occipital alpha-oscillations (8-14 Hz).This shows that cross-modal phase locking of oscillatory visual cortex activity can arise in the human brain to affect perceptual and EEG measures of visual processing in a cyclical manner, consistent with occipital alpha oscillations underlying a rapid cycling of neural excitability in visual areas.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neuroscience and Psychology, University of Glasgow, 58 Hillhead Street, Glasgow G12 8QB, UK. v.romei@ucl.ac.uk

Show MeSH
Related in: MedlinePlus