The Possible Encoding Strategy for Pulse Repetition Rate Processing in Inferior Collicular Neurons of CF-FM Bat, Hipposideros Armiger

The present study examined the effects of pulse duration on the pulse repetition rate (PRR) processing in inferior collicular (IC) neurons of constant frequency-frequency modulation (CF-FM) bat (Hipposideros armiger), using CF-FM sound stimuli of 30+4, 15+3, and 5+2 ms. IC neurons were classified into 4 types: low pass (LP), band pass (BP), high pass (HP), and non-selective neurons. And the proportions of these four types changed with the sound duration decreasing. The LP, BP, and HP neurons might process information from echoes of search, approach, and catch phases, respectively, during bats hunting, while the non-selective neurons had no selectivity to PRR. Because the effects of sound duration on PRR selectivity were distinguishing in different IC neurons, we speculated that some neurons were likely to process their preferred PRRs at one phase of target approaching sequence, while others could adjust their following abilities to match constantly changing duration of sound signals.