(A) Spontaneous time courses of the 24 Hz phase locking between RS1 and LS2 for a representative subject. As illustrated, synchrony (phase-locking values) fluctuated very slowly over time (on the order of secs). Phase locking is plotted relative to the average of 1000 noise simulations using random, Gaussian-distributed noise. (B) The Fourier spectrum of the 24 Hz synchrony between RS1 and LS2. Power increased linearly from the highest to the lowest frequencies. A significant (p < .01) negative linear relationship between frequency and power was seen in 8/10 subjects with an overall highly-significant relationship across subjects (mean R = −.50, t = −5.62, p < .001). Furthermore, the slope of the 24 Hz spectrum was significantly steeper (more negative) than random noise (t = −2.14, p = .03) while the 18 Hz spectrum (not pictured) did not differ from noise (t = −1.31, p > .1) indicating that the high beta frequency synchrony between RS1 and LS2 fluctuates very slowly. (C) Spontaneous time courses of the 10 Hz phase locking between RAud and LAud for a representative subject illustrating that the synchrony varied slowly over time. (D) The Fourier spectrum of the 10 Hz synchrony between RAud and LAud. As in panel B, power increased linearly from the highest to the lowest frequencies, and there was a significant negative linear relationship between frequency and power in 9/10 subjects with an overall highly-significant relationship across subjects (mean R = −.60, t = −13.44, p < .001). Also, the slope of the 10 Hz spectrum was significantly steeper than random noise (t = −3.03, p = .007) while the 20 Hz spectrum (not pictured) was not (t = −0.99, p > .1) indicating that the alpha frequency synchrony between RAud and LAud changes very slowly. Note that while the data B and D were well fit by a negative linear relationship, they were also well fit by a 1/frequency relationship.

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