Background White Noise Affects The Vocalization Behavior And Sound Signal Processing Of Auditory Midbrain In Pratt's Roundleaf Bat

To adapt for living,surviving and proliferation,human and animals can communicate with each other through sound signals.However,the sound signal communication is inevitably influenced by jamming sound.In this case,the sound sender can increase the sound recognition through sound control,and the auditory system of sound receiver will have adaptive changes to increase sound processing efficiency.Inferior colliculus(IC)is considered to be an important nucleus for auditory-motor interaction,which participates in both sound processing and vocal control.In this study,we investigated the effect of background white noise on the vocalization behavior and the intensity tuning and frequency tuning of single IC neuron in Pratt's roundleaf bat(Hipposideros pratti)and obtained the following significant results:1.Under the background white noise condition,the bats showed Lombard effect by increasing its vocal amplitude rather than changing its vocal frequency.The average slope of Lombard effect was 4.4 dB/10 dB.2.Under the background white noise condition,the increase of minimum threshold(MT)was dependent on the background whitenoise intensity,and the slope of threshold change is 7.8 dB/10 dB,while the best frequency(BF)had no significant effect.3.Compared with no background noise condition,the 70 dB SPL background white noise condition could significantly increase the best amplitude(BA)(69.4±23.6 dB SPL vs 81.2±18.0 dB SPL,p<0.001),slope(5.9±9.0%/dB vs 7.3±9.1%/dB,p<0.001)and decrease the dynamic range(DR)(17.2± 17.6 dB vs 11.7± 11.5 dB,p<0.001)of the amplitude tuning curve(ATC),while had no significant effect on the Q10-value(21.9±14.2 vs 20.6±18.9,p>0.05),Q30-value(11.1±10.1 vs 10.8±10.7,p>0.05)and Q50-value(6.3±4.0 vs 6.0±3.4,p>0.05)of frequency tuning curve.4.Compared with non-second-harmonic-tuned neurons,the neurons tuned at the second harmonic had significant less increase in MT change rate(5.9±3.8 dB/10 dB vs 9.8±3.8 dB/10 dB,p<0.001)and the BA change(7.1±4.9 dB SPL vs 16.7±17.0 dB SPL,P<0.01)under background noise condition,while the change of DR(11.0±11.0 dB vs 12.5±12.2 dB,p>0.05)and slope(6.4±3.6%/dB vs 8.3±12.7%/dB,p>0.05)had no significant difference between these two type of neurons.Taking together,Hipposideros Pratti can increase the sound amplitude of its echolocation signal under white noise condition.And the white noise would increase the intensity selectivity to adapt the increase of sound amplitude.These studies can help us to learn the sound recognition and processing under jamming sound condition of human and other mammals.In addition,the present study also can be a reference for vocal learning.