The Influence Of Different Modulation Frequencies On The Thresholds Of Auditory Steady State Response

PARTâ… : ASSR examination in different modulation frequencies of normal hearing adultsObjective: To explore the influence in the thresholds of auditory steady state responses (ASSR) in high and low different modulation frequencies in normal adults,found the best thresholds in different modulation frequencies in awake and sleeping.Methods: 15 adults (30 ears) with normal hearing were selected to ASSR test in awake and sleeping,their age ranged from 20 to 25 years old, the equipment was Audera ASSR from American GSI. The test was performed in two different modulation frequencies (in high and low). The stimulus sounds were presented in monaural by the standard Tip-50 insert phones. ASSR parameters: Carrier frequency (CF) are 0.5,1,2,3,4,6 kHz, modulation frequency(MF)are 46,81 Hz.Results: When MF=46 Hz , the thresholds of ASSR in awake were lower than in sleeping above 1kHz CF (P <0.05) ; When MF=81 Hz,the thresholds of ASSR in sleeping were significantly lower than in awake (P <0.05) ,which thresholds were close to pure tone audiometry (PTA).Conclusion: MF affect the thresholds of ASSR, in low modulation frequency, thresholds of ASSR were better in awake, in high modulation frequency, thresholds of ASSR were better in sleeping. In ASSR testing,different modulation frequencies be choosed in different states. Selected low modulate (46 Hz) frequency in awake, and used high modulate (81Hz) frequency in sleeping. When performed ASSR test,the test values were closer to the actual hearing threshold. PARTâ…¡:ASSR examination in different modulation frequencies of normal guinea pigsObjective: To investigate the influence in different modulation frequencies (MF) of the threshold of ASSR , and establish the best threshold of ASSR in normal guinea pigs.Methods: 12 guinea pigs (24 ears) with normal hearing sedated by pentobarbital sodium were selected to ASSR test. The equipment was Audera ASSR from American GSI. The test were performed in different modulation frequencies ,stimulus sounds were presented in monaural by the standard Tip-50 insert phones. ASSR parameters: carrier frequency (CF) are 0.5,1,2,3,4,6 kHz, modulation frequency (MF) are 21,46,67,74,81,110,154 and 199 Hz.Results:When CF equaled to 0.5 kHz, the threshold of ASSR with MF of 154Hz was lower than other MF, had statistically significant differences (P <0.05) except for MF of 110 and 67Hz ;when CF was amount to 1 kHz, the threshold of ASSR with MF of 199Hz was lowest ,had significant differences to 21,46 and 81 Hz; In CF of 2 kHz, the minimum threshold of ASSR was in 154 Hz , had statistically differences (P <0.05) to 21~74 Hz; In CF of 3 and 6 kHz, the lowest threshold of ASSR was in 199 Hz,compared to 21~81 Hz, there was statistically significant differences (P <0.05); When CF equaled to 4 kHz, there was statistically significant differences (P <0.05) compared to MF of 21~81 Hz.Conclusion:MF affect the thresholds of ASSR,in sedation, the threshold were higher in low modulation frequencies, and were lower in high modulation frequencies. The best MF of ASSR threshold would be between 154 Hz and 199 Hz.