ABSTRACT
Objective To explore whether the changes of sound source in the horizontal azimuth can induce mismatch negativity (MMN) ,and quantify the minimal audible angle which could elicit the MMN and to find effec‐tive way to test human's ability of sound localization in the horizontal plane .Methods With the self developed sound localization device and Bio - logic auditory evoked potentiometer ,in the free field hearing tests were performed on 30 healthy young volunteers according to oddball stimulation sequence .We adopted 1 000 Hz pure tone as the stand‐ard stimuli , the change of sound source location as experimental models ,using minimum audible angle (MAA ) measure procedure ,sound localization test was conducted at 0° ,± 45° ,± 90°standard positions in the horizontal plane .MMN was obtained by subtracting the ERP of deviant stimuli from the ERP of standard stimuli .The latency and amplitude of each MMN were recorded .Results The MMAs of normal young people were recorded and normal values of latency and amplitude of MMN were obtained .The results of the sound localization test for the youth were :MAA(0°)= 2 .09 ± 1 .81° ,MAA( - 45°)= 3 .84 ± 1 .61° ,MAA (45°) = 3 .69 ± 2 .39° ,MAA ( - 90°) = 4 .41 ± 1 . 41° ,MAA(90°)= 4 .23 ± 3 .22° ,separately .There was a significant effect of the location of the deviant stimulus , with those presented at 90° eliciting larger peaks and longer latency period than those presented at 0° .Conclusion Our findings suggest that changes of sound position in the horizontal azimuth can induce mismatch negative waves , and MMN on the basis of MAA test procedure could be used to evaluate the ability of sound localization .
ABSTRACT
BACKGROUND AND OBJECTIVES: The purpose of this study was to determine how human neural activity might be changed through auditory short-term training when listening to novel stimuli. SUBJECTS AND METHODS: Among the twenty young normal hearing adult listeners who participated, ten were randomly assigned to a training group and ten were assigned to a non-training group as a control. Two synthesized novel stimuli were used: /su/ and /integralu/. Both stimuli similarly sounded like /su/, but had two different onset transition frequencies and fricative pole frequencies. In the experiment, behavioral identification test (i.e., /su/ vs. /integralu/) and the mismatch negativity (MMN) were measured before and after training for the training group. To gauge the training effect, the listeners in the training group were taught by discrimination and identification of two novel stimuli for about 20 minutes. RESULTS: The results showed that scores for the behavioral test increased significantly after auditory short-term training. Also, onset latency, duration, and area of the MMN were significantly changed when elicited by the training stimuli. CONCLUSIONS: These findings indicated that auditory short-term training could change human neural activity, suggesting future clinical applications for auditory training.