Extended Data Figure 4: Effect of running speed on oscillation frequency.
From: Coordination of entorhinal–hippocampal ensemble activity during associative learning
a, Power spectra of oscillations in dCA1, pCA1, LEC and MEC as a function of running speed at T5 during random foraging in the 1 × 1 m square box. Power is normalized at each frequency bin and shown as a z-score18. Data were averaged across 9 (dCA1), 14 (pCA1), 10 (LEC) and 8 (MEC) tetrodes from 5 dCA1 and pCA1, 5 LEC and 4 MEC rats, respectively. b, Peak oscillation frequency (mean ± s.e.m. for all tetrodes) as a function of speed bin in a. As in previous work18, a significant correlation was observed between speed and peak frequency of oscillations in the 20–140-Hz range (P < 0.001; r(58) = 0.71, 0.44, 0.60 and 0.59 for dCA1, pCA1, LEC and MEC, respectively). c, d, Speed–frequency relationship in the cue-place association task. Same tetrodes as in a. Data were plotted during the cue sampling period (c) and during subsequent running from the cue sampling port to the food cups (d). Note that during cue sampling, speed was minimal (∼0–1 cm s−1). Strong 20–40-Hz oscillations were observed in dCA1, pCA1 and LEC (arrows in c) but not at similar speeds during running (d). e, In all four brain regions (dCA1, pCA1, LEC and MEC), the power at very low speeds (0–1 cm s−1) was significantly stronger during cue sampling than during running (paired t-test, P < 0.01; t(8) = 3.9, t(13) = 13.7, t(9) = 13.4 and t(7) = 4.5 for dCA1, pCA1, LEC and MEC, respectively), suggesting 20–40-Hz oscillations do not reflect low speed as such. f, During running from cue port to food cups, a significant positive correlation between speed and frequency was observed only in pCA1(P < 0.001, r(58) = 0.48). g, Time spent in each speed bin during the running part of the cued task (means ± s.e.m. for all 14 rats). Note that all speed bins (including low speeds) were sampled for 2.5 s or more.
