Masae Shiroma

Deafness due to A1555G mitochondrial mutation without use of aminoglycoside.

Objectives/Hypothesis: The objective was to clarify the characteristics of deafness associated with the A1555G mutation within mitochondrial 12S ribosomal RNA gene in the absence of aminoglycoside exposure.

Audiological Features and Mitochondrial DNA Sequence in a Large Family Carrying Mitochondrial A1555G Mutation without Use of Aminoglycoside

To elucidate the pathophysiological and genetic mechanisms of hearing loss associated with the homoplasmic mitochondrial A1555G mutation in the absence of aminoglycoside exposure, we conducted audiological and genetic analyses on 67 maternally related members of a large Japanese family carrying this mutation. A consistent pattern was evident in the audiograms, with features of sensory presbycusis, cochlear origin at all levels of hearing loss, and a high degree of vulnerability of outer hair cells. That the degree of hearing loss was similar in affected subjects within the same sibling group but differed between sibling groups suggests the involvement of nuclear modifier genes. Total mitochondrial DNA sequences were completely identical among subjects with various levels of hearing loss, and lacked additional pathogenic mutations. For the diagnosis of sensorineural hearing loss, the mitochondrial A1555G mutation should be considered when these features are present even in the absence of aminoglycoside exposure.

Auditory Evoked Potentials under Active and Passive Hearing Conditions in Adult Cochlear Implant Users

Objectives Speech perception abilities, which vary widely among cochlear implant (CI) users, are considered to be associated with the integrity of the central auditory pathways from the auditory nerve to the cortex. Therefore, auditory evoked potentials (AEPs) are used to evaluate central auditory processing, which is thought to contribute to speech perception in CI subjects. In AEPs, the P300 component reflects the cognitive ability of subjects to detect and respond to stimuli and has most frequently been used and investigated in CI subjects. Other studies have used mismatched negativity (MMN) to examine central auditory processing. It is important to compare MMN and P300 and examine the auditory processing mechanisms involved in these components. Our study therefore aimed to investigate the relationship between P300 and MMN using both active and passive hearing paradigms in CI and normal hearing (NH) subjects. Methods Our subjects consisted of 3 CI subjects and 3 NH subjects. An oddball paradigm was used to deliver the stimuli on both components. The frequent stimuli were 1,000-Hz tone bursts, whereas the rare stimuli were 1,500, 2,000, and 4,000-Hz. Results As the frequency contrasts increased, the P3 latencies increased in the CI subjects. However, the latency in NH subjects did not change significantly across the frequency contrast conditions. MMNs were identified for both the CI and NH subjects; the latencies in the CI subjects were longer than those in the NH subjects. However, there were no differences in the latencies of either the CI or NH subjects in the 3 frequency contrast tasks. Conclusion Our results indicated that different auditory processing pathways are involved in the active and passive hearing conditions based on the P300 and MMN data and that a combination of both responses plays an important role in the comprehension of auditory processing mechanisms in CI subjects.

The Japanese hearing in noise test.

Preparation of test materials A total of 1000 daily-used sentences were constructed by two clinical audiologists. These sentences consisted of 15 to 18 morae per sentence (counting CV or V phoneme as one mora or a syllable) that can be uttered in about two seconds at normal rate. Each sentence was controlled for length (15 to 18 morae, or syllables), for the syntactic structure (noun phrase object verb phrase), and for the phonemic distribution (about 22 different phonemes). They were presented in live voice and were judged by five adults for naturalness using a seven point scale (7 natural, 1 artificial). The 367 sentences that received mean ratings of six or seven were retained. Five other adult subjects then listened to the sentences at about 60 B SPL to judge the naturalness, and a total of 300 sentences remained for recording by a professional Japanese male voice actor. Other sentences judged as unnatural were excluded.

Syntactic development in Japanese hearing-impaired children.

Objectives: This study examined syntactic development of auditory comprehension of sentences in Japanese-speaking school-age children with and without hearing impairment. Methods: In total, 592 preschool and school-age children (421 normal-hearing and 171 hearing-impaired) were included in this cross-sectional observation study conducted using the Syntactic Processing Test for Aphasia for Japanese language users. Linear regression analysis was used to determine the estimated age at which each syntactic structure was acquired. Results: Acquisition of syntactic structures was observed in hearing-impaired and normal-hearing children. Basic word order sentences of agent-object-verb and the goal benefactive construction were acquired at preschool age (earlier group), whereas reverse word order sentences of object-agent-verb, source benefactive construction, passive voice, and relative clauses were acquired at school age (later group). The results showed that many hearing-impaired children may not acquire Japanese grammatical structures until the age of 12 years. Conclusions: Adequate screening for language development for school-age hearing-impaired children is required for an effective intervention.

Binaural integration abilities in bilateral cochlear implant user

Bilateral Cochlear implants (CIs) improved speech intelligibility, speech perception in background noise, and sound localization in quiet and noisy situations. However, it is unclear whether these advantages essentially result in binaural integration of acoustic stimuli from each ear. In this study, we investigated the effectiveness of binaural integration by bilateral CIs placement using binaural hearing tests and subjective auditory perceptual assessment. A 61-year-old bilateral CIs subject underwent the following four tests: the Japanese Hearing in Noise Test (HINT-J), the dichotic listening test (DLT), the Rapidly Alternating Speech Perception (RASP) test, and subjective auditory perceptual assessment. The HINT-J score was significantly higher for bilateral CIs than for a unilateral CI. However, DLT and the RASP test revealed contradictory results. Subjective auditory perceptual assessment revealed active and bright impressions for bilateral hearing, which were also noisy and strong compared with those for unilateral hearing. The results of this study revealed that bilateral CIs improved speech perception in background noise and an improved auditory impression, although the bilateral integration abilities were not improved. This was probably because the patient was required to combine information from the two ears into a single perception in DLT and the RASP test. More longitudinal data should be collected and analyzed in future studies to evaluate the long-term effects of bilateral CIs.

Improving the voice pitch discrimination threshold through cochlear implants

Aiming at the maximum use of linguistic information conveyed by the periodicity pitch of speech sound through cochlear implants, the possibility of improving the voice pitch discrimination threshold was examined for cochlear implantees: three acquired deaf adults and four congenitally deaf children. Female and male adult speech samples of vowel /a/ were analyzed and resynthesized using the STRAIGHT computer program to shift the original voice pitch (c1 and c) one octave upward and downward with a half‐step interval on the musical scale. By presenting those synthetic speech samples in pairs, the discrimination threshold of the voice pitch interval was observed. Association of the speech samples to the picture of a piano keyboard was helpful for conceptualizing the voice pitch change, especially for children. Preliminary observation results suggested that the discrimination threshold can be improved by less than one whole step by adults and two whole steps by children. Those figures were promising because, ...

CAI system for testing and training discrimination ability of change in voice pitch through the cochlear implant

In the cochlear implant, change in voice pitch is transmitted through the periodicity of change in density of neural pulse trains excited by the electrical signal. As the transmission quality of the voice pitch depends on the setting of the processor of each device, it is necessary to measure precisely the discrimination ability of change in voice pitch for each user, and to make maximum use of it. For this purpose, a CAI (Computer Assisted Instruction) system for testing and training the discrimination was developed.