Theta-phase precession of gamma amplitude as a function of running speed.

A) Slow gamma amplitude as a function of theta phase for one example dataset (figure 2F) was averaged across all the theta cycles at low (dashed) and high (solid) speeds. Further, unlike figure 2F, the amplitude of gamma at each phase of theta was divided by the sum of gamma amplitudes across all phases of theta at that speed. This enabled a comparison of the depth of modulation of gamma amplitude with running speed and theta phase, independent of changes in gamma amplitude with running speed. The theta phase modulation of gamma amplitude was 158% greater and the preferred phase of theta was 63° lower at high speeds compared to low speeds B) Same data as A, but as a function of (the logarithm of) a range of running speeds. The hippocampal velo-temporal receptive field for speed (VTRF) for this example dataset shows a progressive precession of slow gamma preferred phase of theta with speed (white dotted line). C) VTRF averaged across all the data show a robust increase in the depth of modulation as well as precession (white dotted line) of slow gamma preferred phase of theta with increasing running speed. D) Same as in A, but for fast gamma showing only a small change in the depth of modulation of fast gamma amplitude (75%) and preferred theta phase (10.7°) with speed. E) Same as B showing only small changes in fast gamma VTRF with speed. F) Same as C showing minimal changes in the ensemble averaged fast gamma VTRF with speed.