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Biomedical subjects

J K Cullen

Publications and source records attributed to J K Cullen.

36 records · Page 2Linked to original sources
PubMed1981

Auditory signal processing in a hearing-impaired subject with residual ultra-audiometric hearing.

A number of hearing-impaired individuals with near-normal thresholds for frequencies above 8,000 Hz who are characterized by good speech articulation have recently been identified. It is unclear whether this unusually good articulation is linked to the ability of such persons to process speech signals containing energy that falls within the range of their residual, high-frequency hearing (for example, certain consonants). This paper reports a detailed study of the signal-processing capabilities of one patient with a long-standing, severe to profound hearing loss in the standard audiometric range, and normal left-ear thresholds in the region of 13,000 Hz. Measures obtained include difference limens for frequency and intensity, gap detection, rate matching, temporal integration, and tone-on-tone masking profiles (psychoacoustical tuning curves). In addition, measures of speech production and perception were made when the patient was using an experimental hearing aid designed to transpose speech range frequencies into the region of her residual high-frequency hearing. Results indicate the patient can efficiently process signals which fall within the band of her best hearing, and suggest her ultra-audiometric hearing may be useful in speech communication.

Adult↗
PubMed1979

Effects of stimulus-onset asynchrony on the dichotic performance of children with auditory-processing disorders.

Dichotic stop-consonant-vowel identification was investigated in two experiments using two groups of learning-disabled children demonstrating clinical manifestations of auditory-processing disorders, and two groups of matched, control subjects. Two-item, forced-choice paradigms were used in both experiments. Overall (total) dichotic performance for the two learning-disabled groups was significantly lower than that of the control subjects in all dichotic conditions. This lower performance was attributable to the number of trials in which both stimulus items were correctly identified. Analysis of trials in which only one response was correct showed no differences between the groups in terms of magnitude or direction of ear-advantage (right). In conditions where stimulus onsets were separated by 30, 90, and 150 msec, analysis of one-correct trials demonstrated more accurate identification of the temporally lagging stimulus for all subjects. However, as the onset-time separation increased, the control group's identification of leading and lagging items approached equality. The learning-disabled group, on the other hand, showed little increase in identification of temporally leading items even when stimuli were separated by 150 msec. These data suggest learning-disabled children with auditory-processing disorders may have a reduced temporal efficiency in processing rapidly varying acoustic patterns associated with stop-consonants that is observable when speech perceptual mechanisms are stressed through dichotic competition.

Auditory Perceptual Disorders↗
PubMed1979

Ear dominance in perception of dichotic chords: pure tones versus tone glides.

Pitch judgments for dichotic chords composed of two pure tones often show a bias in favor of the chord-component going to one ear. This "ear-advantage for pitch" (EAP) varies between subjects, but is very stable within subject and is thought to reflect differences in spectral "sensitivity" of the two auditory pathways. The present study explored this hypothesis by examining pitch judgments of complexes composed of tones dichotically paired with frequency-varying signals. The direction and strength of EAP was first established using pure tones, then rising tone glides were introduced into the channel going to thenondominant ear. Since a glide possesses less energy at a given frequency than a pure tone of equal duration, an increase in EAP was expected. An increase in EAP was consistently observed for only one subject; three subjects showed small, variable effects; and six subjects displayed a decrease in EAP. The results suggested that factors other than relative spectral sensitivity affect observed EAP.

Acoustic Stimulation↗
PubMed1978

Changes in human eighth nerve action potential as a function of stimulation rate.

The primary clinical utility of electrocochleography at the Louisiana State University Medical Center is the detection of hearing losses in children. This frequently requires the administration of a general anesthetic. Time required for this procedure could be shortened if stimuli were presented at a more rapid rate than the customary 10/s, provided the response amplitude is not significantly diminished by adaptation. The response amplitudes of 12 subjects were studied at stimulus rates of 10, 20, 40, and 80/s. An increase of response amplitude on the order of approximately 3:1 over the 10/s rate was found for the 80/s rate when the test interval for each was equal.

Acoustic Stimulation↗
PubMed1978

Temporal integration of tone glides.

Temporal integration of rising and falling tone glides against a 50-2800-Hz background of noise at a sound pressure level of 60 dB re 20 micronPa was studied in two experiments. Glides were in the frequency ranges 200-700 Hz and 1200-1700 Hz for durations of 5-120 ms. Results indicate an asymmetry in the detectability of rising and falling glides of short duration, with rising glides detected at lower signal intensities in both frequency ranges. These effects are discussed in terms of differences in pattern of frequency analysis of identical, but temporally reversed, waveforms.

Acoustic Stimulation↗
PubMed1978

Temporal integration of two-component tone glides.

Temporal integration of complex signals composed of two linearly combined tone glides was studied in a 60-dB SPL noise background. When both glide tones increased or decreased in frequency, integration functions differed for durations shorter than 50 ms in a manner similar to results obtained for single-component tone glides. That is, rising two-component glides were detected at lower thresholds than were falling two-component glides. However, when one component increased in frequency and the other decreased, thresholds were the same, regardless of which component increased and which decreased.

Acoustic Stimulation↗
PubMed1976

Electrocochleography in children. A retrospective study.

A follow-up study of 35 children subjected to electrocochleography (Ecog) was conducted to determine (1) agreement of Ecog results with other audiometric measures obtained subsequently, and (2) accuracy of recommendations for patient management made on the basis of Ecog results. The latter was determined by parental experience, educational placement and achievement, and information from medical and paramedical personnel currently managing the children. These data indicate that Ecog test results are valuable in helping select between possible management alternatives in children who are not testable by behavioral means. However, discussion of two "problem" cases points to possible errors of management that could be made if Ecog results were the only available diagnostic information.

Acoustic Stimulation↗
PubMedDate not supplied

Cochlear microphonic responses of the peripheral auditory system to frequency-varying signals.

Cochlear partition displacement responses to rising and falling frequency sweeps were inferred from cochlear microphonic potentials recorded from three basal turn locations in the guinea pig cochlea. Relative phase measures of microphonic potentials recorded from the three locations suggested that displacements of the partition toward either scala vestibuli or scala tympani occurred closely together in time for rising sweeps and were dispersed in time for falling sweeps. These differences in peripheral response patterns to sweeps may explain, in part, asymmetric neural discharges elicited from higher neural centers.

Animals↗
PubMedDate not supplied

Tone burst electrocochleography in humans.

Using tone burst stimuli with fixed parameters of rise time and duration, a functional relationship has been demonstrated between frequency and intensity of the stimulus and peak latency of electrocochleographic recordings. The feasibility of a "map" of the human cochlear partition has been shown for frequencies above 2 kHz.

Action Potentials↗