Figure 2.

A schematic of the procedures for establishing phase-detection relationships, both independent of other frequencies (Step 1) and taking into account cross-frequency coupling between lower and higher frequencies (Step 2). (A) The hit rate was calculated across trials where the prestimulus phase fell within one-half of the unit circle. This procedure was repeated, with the 180° arc being rotated around the unit circle in 5° steps. (B) The resulting 72 phase-specific hit rates were then converted to a percent change in visual-target detection relative to the overall hit rate, revealing a phase-detection relationship. (C) To describe this phase-detection relationship with a single number, the data were transformed into the frequency domain. The FFT peak associated with one cycle (i.e., the peak that describes a biphasic relationship) represents the fluctuation in hit rates as a function of prestimulus phase, and thus our dependent measure. (D) To determine whether the phase of lower frequencies modulates phase-detection relationships at higher frequencies, we used the same analysis steps (A–C) after first binning trials based on the prestimulus phase of either delta or theta oscillations. Trials were split into two bins: (1) a “good” bin, centered on the phase of the lower-frequency with the highest likelihood of visual-target detection (represented with red), and (2) a “bad” bin, centered on the phase of the lower-frequency with the lowest likelihood of visual-target detection (represented with blue). The data displayed here were taken from Participant 3.