Figure 1.

Schematic representations of power change paradigms. A, A typical set of power spectral densities. P_Task(f) represents the task under observation, and P_ITI(f) represents the corresponding intertrial interval that is the basis for comparison. B, The normalized power spectrum defined in equation form and illustrated schematically. This method of normalization shows the direction and magnitude of power change with reference to a resting state over a range of frequencies. C, Schematic normalized spectra illustrating the hypothesis that high-gamma power change is uniform in nature. Low frequencies (μ, β, <30 Hz) tend to show power decreases for cognitive task while high frequencies have power increases. D, Schematic normalized spectra illustrating the hypothesis that high-frequency power change is nonuniform. Both spectra have power changes in specific bands that distinguish one cognitive task from another.