Figure 10.

Control experiments conducted to verify relationship between SC premotor neural activity and sonar vocalizations. A, Neural recordings were recorded simultaneously with non-sonar calls produced spontaneously by bats. Left, A raster plot and corresponding PMTHs do not show long lead events or short lead events when bats produce non-sonar calls. The raster and PMTHs show SC neural activity aligned with vocal onset (t = 0 ms) for n = 79 non-sonar calls from a single site. Right, Pulse interval, bandwidth, and call duration of non-sonar calls. B, Head movements were tracked during the production of sonar vocalizations. The movement trajectories were normalized, to facilitate cross trial comparisons, using a z-score function. A reduction in the amount of head rotation precedes the expected time (gray bar) of premotor activity. The amount of head motion becomes increasingly variable at less reliable points in time after call onset. Data are from three bats (4 sessions), aligned to sonar call onset (t = 0 ms). Vertical gray bar represents mean time of long lead events ± 1 SD, as recorded in separate virtual target amplitude discrimination experiments. C, No pre-vocal neural activity is observed in the inferior colliculus before sonar vocalizations. Gray dots represent the time of the last call, and black dots are event times. The PMTH shows low firing rates. Sonar pulse intervals range from 20 to 410 ms, similar to the range observed during virtual target discrimination experiments. Sonar call bandwidth, start frequencies (black, filled circles), and end frequencies (black, open circles) are shown for all of the sonar calls produced in this trial. D, Raster and PMTH of electromyogram events recorded from the muscles of mastication on the dorsal surface of the skull. Events around sonar calls (n = 100 sonar calls) are aligned to call onset (lead time of t = 0 ms) and do not show deviations in rate before or after call onset. The event rate remains low (50 ± 5 events/s) around each sonar call onset.