Division Of Processing Doppler-shift Compensation Signal In Inferior Colliculus Of Hipposideros Pratti

Relying on their doppler-shift compensation (DSC) behavior, constant frequency-frequency modulation (CF-FM) bats continuously tune their acoustic frequency to calibrate the echo, and ensure that the echo frequency remains in the frequency band of bats’auditory fovea, enabling the sharpest frequency tuning. This highly-specialized hearing-acoustic control system helps bats to sense their surroundings, avoid obstacles, and successfully catch insects. In this study, we investigated the auditory response properties of inferior collicular (IC) neurons processing DSC signal in Pratt’s roundleaf bat, Hipposideros Pratti, by using in vivo extracellular recordings. And the results obtained were summarized as following:1. In order to investigate the auditory response properties of IC neurons processing DSC signal with different intensities of pulse-echo pairs, we studied the variation of 50% interpulse interval (IPI) of each IC neuron under different pulse-echo pairs with varied echo intensity. According to the shortest 50% IPI (best 50% IPI), we divided the IC neurons into four types:intensity-independent neurons, △20 dB intensity-sensitive neurons, △10 dB intensity-sensitive neurons and △0 dB intensity-sensitive neurons. Our results showed that intensity-independent neurons appeared intensity tolerant characteristics, the best 50% IPI, DSC selectivity, best compensation value, DSC range and DSC area were relatively constant with the intensity of echo increasing. For intensity-sensitive neurons, they only showed the shortest best 50% IPI and best abilities in DSC performance at their preferred echo intensities. These results suggested that IC neurons with different intensity-sensitivities had clear divisions in processing DSC signal under different pulse-echo pair stimulation conditions. Intensity-independent neurons may perceive particular Doppler-shift information because of their invariable abilities of DSC processing. And the different intensity-sensitive neurons may have clear divisions of labor and play important roles in analyzing DSC information in different phases of bats echolocation.2. In this study, we also investigated the roles of harmonic and non-harmonic IC neurons in Pratt’s roundleaf bats’DSC. IC neurons could be classified into four types according to their recoveries under different pulse-echo pairs of DSC. The results implied that IC neurons with different selectivity of DSC in harmonic or non-harmonic might play different roles in processing echo information during bat’s DSC.