Recovery cycle of inferior collicular neurons in Hipposideros pratti under behavior-related sound stimulus and the best Doppler-shift compensation conditions.

The Doppler-shift compensation (DSC) behavior of constant frequency - frequency modulation (CF-FM) bat (Hipposideros pratti) is vital for extraction and analysis of echo information. This type of behavior affects the recovery cycles of sound-sensitive neurons, but their precise relationship remains unclear. In this study, we investigated the effects of DSC on the recovery cycles of inferior collicular (IC) neurons in H. pratti. We simulated the pulse-echo pair in bats by changing the emitted pulse frequency and keeping the echo frequency constant during DSC in echolocation. The neuronal recovery cycles of IC neurons are categorized into four types: unrecovered, monotonic, single-peak, and multi-peak. The recovery cycle of IC neurons shortens after DSC; moreover, the amount of neurons with multi-peak recovery cycle increases and concentrates in the short recovery area. This paper also discusses the possible neural mechanisms and their biological relevance to different phases of bat predation behavior.

Effect of echolocation behavior-related constant frequency-frequency modulation sound on the frequency tuning of inferior collicular neurons in Hipposideros armiger.

In constant frequency-frequency modulation (CF-FM) bats, the CF-FM echolocation signals include both CF and FM components, yet the role of such complex acoustic signals in frequency resolution by bats remains unknown. Using CF and CF-FM echolocation signals as acoustic stimuli, the responses of inferior collicular (IC) neurons of Hipposideros armiger were obtained by extracellular recordings. We tested the effect of preceding CF or CF-FM sounds on the shape of the frequency tuning curves (FTCs) of IC neurons. Results showed that both CF-FM and CF sounds reduced the number of FTCs with tailed lower-frequency-side of IC neurons. However, more IC neurons experienced such conversion after adding CF-FM sound compared with CF sound. We also found that the Q 20 value of the FTC of IC neurons experienced the largest increase with the addition of CF-FM sound. Moreover, only CF-FM sound could cause an increase in the slope of the neurons' FTCs, and such increase occurred mainly in the lower-frequency edge. These results suggested that CF-FM sound could increase the accuracy of frequency analysis of echo and cut-off low-frequency elements from the habitat of bats more than CF sound.