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Biomedical subjects

Emily Buss

Publications and source records attributed to Emily Buss.

24 records · Page 2Linked to original sources
PubMed2002

The effect of temporal stimulus characteristics in maintenance of the acoustic reflex.

In normal listeners, acoustic reflex decay (ARD) typically occurs for high- but not for low-frequency tones. In patients with acoustic neuromas, decay can be obtained at all frequencies, presumably due to poor neural synchrony. These observations have led us to hypothesize that resistance to decay is due to robust encoding of temporal fine structure of the eliciting stimulus. For a 4-kHz stimulus, ARD is reduced by sinusoidal amplitude modulation (SAM), a result attributed to the low-frequency pattern of SAM providing the temporal characteristics necessary to maintain the reflex. If this interpretation is correct, then further reductions in ARD should be seen for stimuli having temporal characteristics that even more closely resemble the neural response to low-frequency stimulus fine structure. On the other hand, if other perceptual qualities of a SAM tone are responsible for the effect (e.g., rate pitch), then manipulations of perceived sound quality, rather than temporal characteristics per se, should produce similar effects. The experiment reported here included a reference condition, (1) 5-kHz pure tone, and three "temporal" manipulations, composed of a 5-kHz tone multiplied by (2) a raised 100-Hz sinusoid, (3) a noise sample, lowpass filtered at 100 Hz, and (4) a half-wave rectified 100-Hz sinusoid. Additional conditions manipulated perceived pitch. These stimuli spanned 4.5-8 kHz, including a reference condition, (5) Gaussian noise, and a stimulus associated with a 100-Hz pitch, (6) iterated rippled noise. Results show the greatest reductions in ARD with the half-wave rectified stimulus, thought to most closely mimic the temporal characteristics of a low-frequency tone. Little or no reduction in ARD was associated with the iterated rippled noise, suggesting that perceived pitch does not play an important role in maintaining the acoustic reflex.

Acoustic Stimulation↗
PubMed2002

Spondee recognition in a two-talker masker and a speech-shaped noise masker in adults and children.

OBJECTIVE: The objective of the study was to examine developmental effects for perceptual masking due a two-talker masker. Both continuous and gated maskers were employed in order to determine the importance of masker continuity for perceptual masking. DESIGN: A repeated measures design compared the spondee recognition performance of adults and children using both a speech-shaped noise and a two-talker masker. The masker was either presented continuously, or was gated on and off at about the same time as the target spondee. The ages of the listeners were 19 to 48 yr (adults) and 5 to 10 yr (children). RESULTS: The results for the continuous masker indicated higher thresholds for the two-talker masker than for the speech-shaped noise masker. This effect was greater in the children than in the adults. In the gated masking condition, the greater masking effect associated with the two-talker masker was either diminished (children) or eliminated (adults). CONCLUSIONS: These results suggest a masking effect for two-talker speech competition that is greater in children than in adults. Perceptual masking is greater for continuous than for gated masking.

Adult↗
PubMed2002

Outcome of cochlear implantation in pediatric auditory neuropathy.

OBJECTIVE: Auditory neuropathy, characterized by absence or abnormality of auditory brainstem responses and normal otoacoustic emissions, is often associated with particularly poor response to amplification. Outcome data from four such pediatric patients who received cochlear implants are discussed. STUDY DESIGN: Four patients from the Carolina Children's Communicative Disorders Program were identified as having received a diagnosis of auditory neuropathy before implantation with a Clarion cochlear implant. Speech data collected after implantation were compared with data from control pediatric implant patients, matched for age at implantation and duration of implant use. Electrically evoked auditory brainstem response data and electrically evoked acoustic reflex data were also obtained. METHODS: Routine clinical procedures were used to obtain speech outcome data. A 75-micros biphasic 21.1-Hz pulse train served as the eliciting stimulus for both evoked auditory brainstem responses and reflex measures, which were obtained contralateral to the implant. RESULTS: Speech data were comparable with those obtained from the general population of pediatric patients receiving cochlear implants at this center. Identifiable evoked auditory brainstem response data were obtained in all subjects on at least two of the three electrodes tested, and variability was comparable with that observed in other children with implants. A robust electrically evoked acoustic reflex with no decay was observed at estimated M-level in all children. CONCLUSION: The data gathered to date suggest that the outcome of cochlear implantation in these four patients is not significantly different from that in other pediatric implant patients. Physiologic data suggest that the implant was able to overcome the desynchronization hypothesized to underlie auditory neuropathy.

Child, Preschool↗
PubMed2002

Virtual pitch integration for asynchronous harmonics.

This experiment examined the generation of virtual pitch for harmonically related tones that do not overlap in time. The interval between successive tones was systematically varied in order to gauge the integration period for virtual pitch. A pitch discrimination task was employed, and both harmonic and nonharmonic tone series were tested. The results confirmed that a virtual pitch can be generated by a series of brief, harmonically related tones that are separated in time. Robust virtual pitch information can be derived for intervals between successive 40-ms tones of up to about 45 ms, consistent with a minimum estimate of integration period of about 210 ms. Beyond intertone intervals of 45 ms, performance becomes more variable and approaches an upper limit where discrimination of tone sequences can be undertaken on the basis of the individual frequency components. The individual differences observed in this experiment suggest that the ability to derive a salient virtual pitch varies across listeners.

Adult↗
PubMedDate not supplied

Ménière's disease: effects of glycerol on tasks involving temporal processing.

The present study examined the effect of glycerol ingestion on aspects of auditory performance in subjects having Ménière's disease. It was hypothesized that Ménière's disease may be associated with abnormal firing in the auditory nerve and that this should result in a decreased ability to code the auditory temporal fine structure. Psychoacoustical measures of interaural time discrimination and quasi frequency modulation rate discrimination were used as measures of temporal coding, and performance on these tasks was examined both before and after glycerol ingestion. Pre- and postglycerol measures of speech recognition and audiometric thresholds were also obtained. In agreement with previous results, glycerol-related changes in audiometric thresholds were modest or absent, but improvements in speech recognition were relatively reliable. Improvements in interaural time discrimination and quasi frequency modulation rate discrimination were also observed. The results provide limited support for the hypothesis that Ménière's disease may be associated with a reduced ability to code the temporal fine structure of sound.

Adult↗