(A) Top: walking sound recording in sound pressure waveforms (black and green boxes denote 2 sec periods during baseline and walking, respectively, used for power spectrum calculation and playback). Bottom left: picture of the recording setup. Bottom right: normalized power spectrum (black trace: baseline, green trace: walking). (B) Recordings of walking sound (green), and walking sound playback at different sound levels (25, 30, 35, and 40 dB). The playback sound levels were determined from RMS values of thresholded events shown as magenta in the 40 dB waveform. (C) Sound levels of recorded playbacks in B, relative to the level of the walking sound recording (horizontal green dashed line). Sound levels were obtained from whole traces (black) or only from the events (magenta), In both cases, the recording of 30 dB playback was the closest to that of walking sounds. The same events were used for all playback levels and walking sound recording. (D) Example neuron showing a strong positive modulation during locomotion (left; ∆<r> = 11.4 Hz), but weak responses to playback (right; ∆<r> = 2.0 Hz at 30 dB, and ∆<r> = 0.8 Hz at 40 dB). (E) Example neuron showing a suppression during locomotion (left; ∆<r> = −10.3 Hz), but excitatory responses to playback (right, ∆<r> = 8.1 Hz at 30 dB and ∆<r> = 10.9 Hz at 40 dB; in this example, the first 0.5 s of the stimulus period was excluded for firing rate measurement due to the response during the initial baseline period). (F) Average firing rate changes (∆<r> ) during locomotion vs. the changes by walking sound playback at 30 dB (n = 25; r = 0.16, p=0.44). Red and blue squares represent the neurons in D and E, respectively. (G) Same as F, but for playback at 40 dB (n = 20, five neurons excluded due to substantial responses to the recording baseline; r = 0.33, p=0.15). Red square is the neuron in D. The neuron in E was one of the five excluded neurons.