Darrell E. Rose

Cochlear Implants in Prelingually Deaf Children.

All private and public residential and day schools for the deaf in the U.S. that have 100 or more students were surveyed to see how many prelingually deafened students they had with cochlear implants and how many of these students were still using the device. Responses came from 70% (45 of 64) of those schools surveyed. Of the 151 implanted children identified, 71 (47%) were no longer using the cochlear implant. Of the remaining 80 children (53%) still wearing the device, we could not specifically determine by survey the percentage who derived significant benefit from the device and the percentage who did not. However, numerous comments by those returning the questionnaires indicated despondency over the results of the implant.

Summated potentials evoked by speech sounds for determining cerebral dominance for language.

Ten normal adult right-handed subjects receive phonemic combinations (/epik/, /epak/, /a/, /pi/, /pa/) and pure tones (2500 and 8000 Hz) binaurally through matched earphones. Fifty responses from electrodes at P5, P6, C5, C6, F7 and F8 (referenced to linked mastoids) were summated, and evoked potentials from homologous areas were measured separately and superimposed in order to observe differences. Visual inspection of superimposed responses showed no consistent gross asymmetries that lateralized to either hemisphere. Comparison between amplitude of evoked potentials (N1, P2) at P5 and P6 were not significant (P < 0.05; paired t test). We suggest that our technique may not be a useful clinical test for cerebral dominance.

Hemispheric potentials evoked by speech sounds during discrimination tasks

We studied the feasibility of adapting the method of Wood et al. (1971) for determining cerebral dominance for language and did not obtain consistent asymmetries of evoked responses in the left hemisphere to stop consonant task (SCT) as compared with fundamental frequency task (FFT). Likewise, the right hemisphere-evoked potentials for SCT and FFT did not show consistent asymmetries. However, we did find that the evoked responses at T3 were attenuated as compared with those at T4, regardless of the task performed (FFT or SCT). These findings may be useful in developing a test for cerebral dominance for language.

Effects of Intensity Variations on Auditory Processing in Aphasia I. Equal Intensities at Each Ear

Clinical observations have led several authors to suggest that talking louder improves auditory comprehension for the aphasic patient, while others suggest that it does nothing to help comprehension. To clarify these observations under experimental conditions, four measures of auditory processing (cortical-evoked responses, nonverbal intensity sequencing, phoneme in word discrimination and sequencing, and a semantic-syntactic measure of comprehension) were used in diotic presentation of stimuli to 10 aphasic subjects with left temporal lobe damage. The stimuli were presented at 70, 85, and 100 dB SPL. Results suggest that a simple diotic (true binaural) increase of stimulus intensity is not a potent variable for influencing auditory processing in patients with aphasia. Although a few subjects improved their performances on selected levels when stimulus intensity was increased, the performances of others decreased. Auditory-evoked response (AER) latencies and amplitudes generally were not significantly different between the damaged and intact hemispheres. The time-intensity trading function was demonstrated with the AER, particularly for the N2 component. The ear with the greatest advantage on dichotic listening was contralateral to the lesion and was contralateral to the hemisphere that had the shorter P1 latencies, longer N2 latencies, and smaller AER amplitudes.

Noise and hearing loss.

Audiology is an essential aid to diagnosis of hearing loss, including loss due to exposure to excessive noise. Patients who complain of hearing difficulty should be examined and their hearing tested to determine hearing acuity, speech reception threshold, and speech discrimination as well as whether amplification is warranted.