Average power (for correct, rewarded laps only) was then plotted as a function of both position on the linearized track, and lap number (Figures 5C,D). Averages over laps and position are shown to the top and to the right respectively. The spatial averages confirm that gamma-50 power rises sharply upon reaching the reward sites (F1 and F2, grey vertical lines), and persists after departure from F2 before returning to baseline. In contrast, the spatial distribution of gamma-80 power exhibited a very different pattern: it ramped up slowly to the reward sites, returning to baseline comparatively rapidly. Note how gamma-50 power peaks after the reward site locations, while gamma-80 power peaks before. A potential concern in this analysis is the width of the time window used in computing the spectrograms (0.5 s) which could smooth localized transients. To address this, we repeated the above analysis with 250 ms and 1 s windows, which yielded essentially the same pattern, including ramping up of gamma-80 and persistence of gamma-50 following reward site departure, indicating that these phenomena were unlikely to result from artifactual smoothing.
