Effects Of Low-intensity Noise Exposure On Plasticity In The Auditory Center Of Juvenile Guinea Pigs

Objective To study the effects of repeated exposure to 85 dB SPL white noise on auditory acuity,auditory central nerve activity and suprathreshold auditory behavior of juvenile guinea pigs,and to explore the relationship between the plasticity of auditory center and auditory behavior,so as to provide an experimental basis for the study of the hidden harm of low intensity steady-state noise.Methods Select 18 two-week-old male guinea pigs,12 in the experimental group and 6 in the control group.The experimental group was exposed to 85 dB SPL white noise for 12 hours per day for 4 weeks.Then auditory electrophysiological(DPOAE,ABR,GIN-ABR)tests and auditory behavior(ASR,Gap-PPI)tests were performed at three time points(the first day,the 7th day,the 21th day after exposure).The control group was fed in the animal center for the comparison of the same period.Independent sample T test was performed on the results of the two groups at three test time points to compare the differences in auditory acuity,auditory behavior and auditory central nervous response between the two groups.Results 1.On the first day after exposure,the DPOAE thresholds of the experimental group at 12,16,and 24 kHz were significantly higher than those of the control group(12,16 kHz,P<0.01;24 kHz,P<0.05);The ABR threshold of the experimental group in each frequency band was significantly higher than that of the control group(P<0.01),the latency of wave I was significantly greater than that of the control group(P<0.01),the amplitude of ABR wave Ⅰ at 6,8,and 16 kHz was lower than that of the control group(6 kHz,P<0.01;8 kHz,P<0.05),the amplitude of ABR wave Ⅳ at 24 kHz was significantly lower than that in the control group(P<0.01);The recovery rate of GIN-ABR wave Ⅰ in the experimental group at 16 and 32 ms silent gap pulse train was significantly lower than that in the control group(16 ms,P<0.05;32 ms,P<0.01),the recovery rate of GIN-ABR wave Ⅳ at the 8 ms silent gap pulse train was significantly lower than that of the control group(P<0.05);The startle reflex amplitude of the experimental group to the 90 dB SPL stimulation sound was significantly lower than that of the control group(P<0.01);The results of Gap-PPI test showed no difference between groups.2.On the 7th day after exposure,the DPOAE threshold of the experimental group at 16 kHz was significantly higher than that of the control group(P<0.01);The ABR threshold and waveⅠ latency of the experimental group at 6,8,12,and 16 kHz were significantly higher than those of the control group(P<0.01),the amplitude of wave Ⅰ at each frequency band was no different from that of the control group,and the amplitude of ABR wave Ⅳ at 6 and 24 kHz was significantly lower than that of the control group(6 kHz,P<0.05;24 kHz,P<0.01);There was no difference in the results of GIN-ABR,ASR,Gap-PPI tests between the experimental group and the control group.3.On the 21st day after exposure,the DPOAE threshold of the experimental group at 16 kHz was significantly higher than that of the control group(P<0.01);The ABR threshold of the experimental group at 6 and 16 kHz was significantly higher than that of the control group(P<0.01),the latency of wave Ⅰ at 6,8,12,and 16 kHz was significantly greater than that of the control group(P<0.01),and the amplitude of wave Ⅳ at 16 and 24 kHz was significantly smaller than that of the control group(P<0.01);The recovery rate of GIN-ABR wave Ⅰ in the experimental group was only significantly different from that in the control group at the 8 ms silent gap pulse train(P<0.01);The startle reflex amplitude of the experimental group to the 90 dB SPL stimulus sound was significantly greater than that of the control group(P<0.05);There was no difference between the groups of Gap-PPI test results.Conclusion 1.Long-term exposure to 85 dB SPL noise significantly impaires the auditory acuity of guinea pigs in the high frequency band(in the exposed frequency band).2.Exposure induces positive central gain in the low frequency(6 kHz)and negative central gain in high frequency(16,24 kHz)of guinea pigs,suggesting that 85dB SPL noise has complex plastic effects on auditory center during development.3.Long-term exposure to 85 dB SPL noise makes guinea pigs allergic to high intensity sound,that is,loudness perception disorder.