Auditory steady-state response (ASSR) is widely used in clinical practice as an objective audiometric test with frequency specificity. Eclipse version 1.02 by Interacoustics, which uses CE-Chirp^®, is available in two modulation frequencies: 40 Hz and 90 Hz. The stimulation frequency of 40 Hz is recommended for adults in the awake state, while that of 90 Hz is recommended for children in the asleep state. However, in actual clinical practice, some children could be awake during the testing, and some adults could be asleep during the testing. In this study, we measured the ASSR thresholds in the same subject under both awake and asleep conditions and examined the relationship between the results of each test and the pure tone hearing thresholds. The results showed that the results of ASSR measured at both stimulation frequencies were strongly correlated with the pure tone hearing thresholds. In addition, the results for each level of hearing loss showed that the ASSR thresholds were higher than the pure tone thresholds in the normal-hearing group and lower in the severe hearing loss group at all frequencies.

　In the present study, to clarify the effectiveness of simultaneous bilateral cochlear implant (CI) surgery, we compared the scores of the LittlEARS^® Auditory Utilization Questionnaire (LEAQ) and results of the K-test during the first two years after the surgery between 13 patients who had undergone simultaneous bilateral CI (sim-CI group) and 13 patients who had undergone sequential bilateral CI (seq-CI group). The LEAQ scores were significantly higher in the sim-CI group than in the seq-CI group from 3 to 15 months postoperatively, indicating that the sim-CI group showed faster auditory development than the seq-CI group. The developmental index (DQ) in the language and social domain of the K-test (LS-DQ) was significantly higher in the sim-CI group than in the seq-CI group at one year postoperatively, but this significant difference between the two groups was no longer seen at two years postoperatively. Interestingly, the differences in the DQ in the cognitive and adaptive domains and LS-DQ (CA-LS difference) were significantly smaller in the sim-CI group than in the seq-CI group at both 1 and 2 years postoperatively, suggesting that for at least two years after the surgery, the sim-CI group showed a greater degree of language development than the seq-CI group, approaching their own cognitive development level.

　Event-related potentials, such as MMN and P300, are used to evaluate the central auditory perception and are expected to be applied useful for the diagnosis of auditory processing disorders; however, they are not widely used in general audiology laboratories due to the complicated testing procedures and long testing times. In order to shorten the measurement time, we examined the effect of the position of the electrode on the latency in six normal-hearing adult ears using Fz, which is often used in MMN, and Cz, which is usually used in ABR. In addition, we investigated MMN and P300 in 49 ears using Cz and examined the number of additions required for obtaining a stable recording. The results revealed no significant differences in the amplitude or latency depending on the position of the electrode, and the measurement rate was the highest when the number of additions was 200 as compared to 100 or 300, for both MMN and P300. We believe that the MMN and P300 tests can also be developed into practical clinical tests by setting the electrode to Cz and the number of additions to 200.

　We examined monosyllable speech perception in 165 pediatric patients with congenital severe hearing impairment with cochlear implants at elementary school entry. The effects of lip reading, percent correct scores for each syllable, and factors involved in performance were examined, and the following results were obtained.

　1) The average monosyllable speech perception score in the pediatric CI users was 60.7%. The average score improved by 5.1 points in the lip reading condition.

　2) The average percent correct scores for vowels were 87.1%. There was a significant correlation between the overall score and the score for vowels. However, there were cases in which the overall score was lower than 60%, even though the scores for vowels were over 90%.

　3) The percent correct scores were higher for voiceless sounds than for voiced sounds, and the scores for? frictional sounds were much better. The scores for semi-vowels were higher than those for vowels and other syllables. Differences were found in the scores for individual syllables with the same phonemes.

　4) Cases with inner ear malformations, cochlear nerve hypoplasia, developmental disorders, and older age at CI were often seen in the group with a score of one SD below the mean (n=26). An overlap of these conditions accounted for 89% of the cases.

　5) Excluding the above factors, the average score of the "standard cases" reached 75.7% in the auditory alone condition. The age at implantation and performance IQ exerted influence on the monosyllable speech perception ability.

　The developmental changes in monosyllable speech perception ability were evaluated in 50 pediatric profound congenital hearing impairment patients with cochlear implants (CIs), in whom the CI surgery had been performed before the age of 4 years. The scores at elementary school entry and at upper grades of school were compared. Cases of inner ear malformations, cochlear nerve deficiency, and developmental disorders were excluded from the analysis.

　1) The average monosyllable speech perception score of the standard pediatric CI users at the upper grades of school was 84%. The majority of cases showed improvement of the scores as compared to the scores at elementary school entry, with an average improvement of the score by 11.5 points.

　2) The correct scores for vowels reached 99%, on average, at upper grades of school, with the score being 100% in most cases.

　3) The percentage of correct answers was higher for voiceless sounds than that for voiced sounds at both measurement points. The scores for frictional sounds and semivowels were higher than those for vowels and other CV syllables.

　4) Among the syllable groups with the same phoneme, there was divergence in the percentage of correct responses and improvement in school-age children.

　5) Mishearing of /n/, /k/, and /m/ was common, and the most common errors within the same articulatory gestures were for nasals and plosives.

　6) There was a significant negative correlation between the improvement point and the VIQ. For children with insufficient spoken language skills at elementary school entry, it is necessary to monitor the improvement of their listening ability during the school years.