Effects of aging and gender on interhemispheric function.

The ability of the two hemispheres of the brain to communicate with one another via the corpus callosum is important for a wide variety of sensory, motor, and cognitive functions, many of them communication related. Anatomical evidence suggests that aging results in structural changes in the corpus callosum and that the course over time of age-related changes in corpus callosum structure may depend on the gender of the individual. Further, it has been hypothesized that age- and gender-related changes in corpus callosum structure may result in concomitant decreased performance on tasks that are reliant on interhemispheric integrity. The purpose of this study was to investigate the effects of age and gender on auditory behavioral and visuomotor temporal indices of interhemispheric function across the life span of the normal adult. Results from 120 consistently right-handed adults from age 20 to 75 years revealed that interhemispheric integrity, as measured by dichotic listening, auditory temporal patterning, and visuomotor interhemispheric transfer time tasks, decreases relatively early in the adult life span (i.e., between the ages of 40 and 55 years) and shows no further decrease thereafter. In addition, the course over time of interhemispheric decline is different for men compared to women for some tasks. These findings suggest that decreased interhemispheric function may be a possible factor contributing to auditory and communication difficulties experienced by aging adults. In addition, results of this study hold implications for the clinical assessment of interhemispheric function in aging adults and for future research into the functional ramifications of decreased multimodality interhemispheric transfer.

Comparison of two hearing aid receiver-amplifier combinations using sound quality judgments.

Sound quality judgments were obtained on two binaural pairs of laboratory hearing aids with similar battery drain. One pair had a traditional low-current-drain "starved Class A" output stage. The other had a new (at the time) "Class D" output stage. Speech and music reproduction was rated, for seven input levels between 70 and 100 dB SPL, on an overall quality scale by juries of normal-hearing and hearing-impaired subjects. The same subjects also were asked to assign a dollar value to each condition by answering the question "What would you pay for a hearing aid that sounded like that?" Both subject groups rated the hearing aids with the Class D output stage as having superior sound quality across a variety of input levels and test materials, consistent with objective distortion measurements. On the average, each one-percentage point increase in sound quality rating corresponded to a $6.75 increase in perceived value in these experiments.

Hearing loss, aging, and speech perception in reverberation and noise.

The present investigation examined the effect of reverberation and noise on the perception of nonsense syllables by four groups of subjects: younger (less than or equal to 35 years of age) and older (greater than 60 years of age) listeners with mild-to-moderate sensorineural hearing loss; younger, normal-hearing individuals; and older adults with minimal peripheral hearing loss. Copies of the Nonsense Syllable Test (Resnick, Dubno, Huffnung, & Levitt, 1975) were re-recorded under four levels of reverberation (0.0, 0.6, 0.9, 1.3 s) in quiet and in cafeteria noise at +10 dB S:N. Results suggest that both age and amount of pure-tone hearing loss contribute to senescent changes in the ability to understand noisy, reverberant speech: pure-tone threshold and age were correlated negatively with performance in reverberation plus noise, although age and pure-tone hearing loss were not correlated with each other. Further, many older adults with minimal amounts of peripheral hearing loss demonstrated difficulty understanding distorted consonants.

Reference thresholds for the ER-3A insert earphone.

Several recent studies have demonstrated that the ER-3A insert earphone may sometimes be directly substituted, without recalibrating, for a TDH-39/MX-41AR earphone. However, most available data have not been reduced to a form suitable for establishing a revised estimate of the reference threshold levels. This article reports such a data analysis performed on the results of five recent studies. The mean data from the five studies are typically within 1 dB of the provisional reference threshold SPLs given by the ER-3A manufacturer for calibration in a (HA-1) 2-cc coupler. After converting the mean data to equivalent Zwislocki-coupler-type ear simulator SPLs at each of the reported audiometric frequencies (125, 250, 500, 1000, 2000, 3000, 4000, 6000, and 8000 Hz), agreement within 1.5 dB was seen with the revised estimate of minimum audible pressures given by Killion [J. Acoust. Soc. Am. 63, 1501-1508 (1978)]. Either the manufacturer's provisional SPLs or the average results from this study may be used with little noticeable difference for most purposes.

Normal and learning disabled children's central auditory processing skills: an experimental test battery.

The performance of normal children (N = 13) and learning disabled children (N = 26) on an experimental battery of central auditory processing (CAP) tasks was examined. The battery included low-pass filtered speech (LPFS), binaural fusion (BF), time-compressed speech (TC), and dichotic monosyllables (DM) tests. The learning disabled subjects were classified as having normal (LD/N) or significantly impaired (LD/LD) auditory perceptual skills on the basis of a pretest battery of auditory language tests. The normal (N/N) subjects and nonauditory learning disabled (LD/N) subjects tended to perform alike across measures. The auditorily impaired (LD/LD) subjects tended to perform significantly poorer than their normal agemates. The results emphasized the heterogeneity of the learning disabled population. In addition, the results suggested a potentially useful "at risk" criterion when a CAP test battery is used in the assessment of auditory perceptual impairment among children.