Tsuneo Harashima

On chronological changes in the basic EEG rhythm in persons with Down syndrome - with special reference to slowing of alpha waves.

The authors tried to know specificity of aging in persons with Down syndrome (DS) from the aspect of electroencephalograph (EEG) frequency changes through the cross-sectional and longitudinal studies, in comparison with normal persons as well as those with mentally retardation except the Down syndrome (non-DS MR). Subjects for a cross-sectional study were 265 persons with DS, 242 with non-DS MR and 239 healthy persons, and subjects for a follow-up study were 28 persons with DS and 14 with non-DS MR, whose EEGs were recorded repeatedly once a year during 8 or 9 years. Resting EEGs from the frontal, central and occipital regions were examined through power spectrum. In the cross-sectional study, the number of subjects with DS who showed dominant component within 8 Hz band of the basic rhythm reached maximum in its appearance rate at 40-44 years of age in the occipital area, but this slowing progressed already at 30-34 years of age. While in non-DS MR, the number of subjects who showed dominant component at 8 Hz reached maximum at 45-49 years of age, and this slowing of the basic rhythm was not so clear as in DS. In the follow-up study for subjects with DS, although the lowering in EEG frequency to 8 Hz took place in various years of age individually, earlier distinct decrease of the frequency was commonly noticed. These earlier steep lowering of EEG frequency was discussed in relation to the senile signs and to the decline of brain function referring to Alzheimer disease.

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.

Age-related changes in auditory and cognitive abilities in elderly persons with hearing aids fitted at the initial stages of hearing loss

In this study, we investigated the relation between the use of hearing aids at the initial stages of hearing loss and age-related changes in the auditory and cognitive abilities of elderly persons. 12 healthy elderly persons participated in an annual auditory and cognitive longitudinal examination for three years. According to their hearing level, they were divided into 3 subgroups - the normal hearing group, the hearing loss without hearing aids group, and the hearing loss with hearing aids group. All the subjects underwent 4 tests: pure-tone audiometry, syllable intelligibility test, dichotic listening test (DLT), and Wechsler Adult Intelligence Scale-Revised (WAIS-R) Short Forms. Comparison between the 3 groups revealed that the hearing loss without hearing aids group showed the lowest scores for the performance tasks, in contrast to the hearing level and intelligibility results. The other groups showed no significant difference in the WAIS-R subtests. This result indicates that prescription of a hearing aid during the early stages of hearing loss is related to the retention of cognitive abilities in such elderly people. However, there were no statistical significant correlations between the auditory and cognitive tasks.