Sensory stimuli dominate over rhythmic electrical stimulation in modulating behavior
Fig 5
Experiment 3, EEG. (a) Cartoon depicting the stimulus design.
Participants listened to sounds modulated at different frequencies and detected gap periods presented in different phase bins of the modulation cycle. (b) EEG Amplitude spectra separated by FM frequency. The dashed vertical lines mark the FM frequency (in color) and first harmonic (black). Average group data are shown in blue, whereas individual data are shown in gray. (c) Resultant vector length spectra separated by the FM rate. The colors follow the same convention as in (b). (d) Normalized amplitude values quantifying neural entrainment to the FM stimulus separated by frequency. The amplitude values in (b) were normalized by dividing the amplitude of the EEG activity observed at each FM frequency during the presentation of the FM stimulus at a specific frequency by the mean amplitude recorded at that frequency when the FM stimulus was presented at all other frequencies. (e) Normalized resultant vector length as a function of FM frequency. Normalization was performed as described in (d). (f) Optimal FM frequency (rate) for neural entrainment (FM frequency with the highest normalized resultant vector length). (d–f) Each dot represents a single participant. (d–e) Box plots show the median (horizontal black lines), mean (black cross), 25th and 75th percentiles (box edges), and extreme data points not considered outliers (±2.7σ and 99.3 percentiles, whiskers). Red crosses represent outliers (more than 1.5 of the interquartile range away from the bottom or top of the box). Solid red lines display the best fit from the linear model, and dashed red lines show the 95% confidence intervals. Numerical data for panels d and e can be found in [32].