Biomedical subjects

John H Grose

Publications and source records attributed to John H Grose.

13 recordsLinked to original sources

PubMed2004

Duration discrimination in listeners with cochlear hearing loss: effects of stimulus type and frequency.

This study examined the effects of cochlear hearing loss on the ability to discriminate increments in the duration of a stimulus under conditions where the frequency and/or amplitude of the stimulus change dynamically. Three stimulus types were used: pure tones, frequency-modulated tones, and narrow bands of noise. The carrier/center frequency of each 250-ms stimulus either remained constant at 1035 Hz or varied randomly from presentation to presentation across the frequency range 432-2804 Hz. Two groups of listeners participated: 9 with bilateral cochlear hearing loss and 7 with normal hearing sensitivity. The results showed no differences in performance between the 2 groups. However, both groups showed poorer duration discrimination for the conditions where the carrier/center frequency changed randomly than for the conditions where the carrier/center frequency remained constant. In addition, performance was poorer for the narrowband noise stimuli than for the tonal stimuli. This pattern of results suggests that across-frequency temporal judgments are more difficult than isofrequency temporal judgments, but that cochlear hearing loss does not exacerbate this difficulty per se.

Acoustic Stimulation↗

PubMed2004

Developmental effects in the masking-level difference.

Adults and children (aged 5 years 1 month to 10 years 8 months) were tested in a masking-level difference (MLD) paradigm in which detection of brief signals was contrasted for signal placement in masker envelope maxima versus masker envelope minima. Maskers were 50-Hz-wide noise bands centered on 500 Hz, and the signals were So or Sp 30-ms, 500-Hz tones. In agreement with previous studies, it was found that MLDs were greater for masker envelope minima placement than for masker envelope maxima placement. Across the age range of the children tested here, the binaural advantage associated with the masker envelope minima increased with the age of the child. One interpretation of the present results is that there is a developmental improvement in binaural temporal resolution over the age range tested here.

Acoustic Stimulation↗

PubMed2004

Temporal fine-structure cues to speech and pure tone modulation in observers with sensorineural hearing loss.

OBJECTIVE: The purpose of this study was to examine the effect of sensorineural hearing loss on the ability to make use of fine temporal information and to evaluate the relation between this ability and the ability to recognize speech. DESIGN: Fourteen observers with normal hearing and 12 observers with sensorineural hearing loss were tested on open-set word recognition and on psychophysical tasks thought to reflect use of fine-structure cues: the detection of 2 Hz frequency modulation (FM) and the discrimination of the rate of amplitude modulation (AM) and quasifrequency modulation (QFM). RESULTS: The results showed relatively poor performance for observers with sensorineural hearing loss on both the speech recognition and psychoacoustical tasks. Of particular interest was the finding of significant correlations within the hearing-loss group between speech recognition performance and the psychoacoustical tasks based on frequency modulation, which are thought to reflect the quality of the coding of temporal fine structure. CONCLUSIONS: These results suggest that sensorineural hearing loss may be associated with a reduced ability to use fine temporal information that is coded by neural phase-locking to stimulus fine-structure and that this may contribute to poor speech recognition performance and to poor performance on psychoacoustical tasks that depend on temporal fine structure.

Adult↗

PubMed2004

Spectral integration of synchronous and asynchronous cues to consonant identification.

The goal of the present research was to determine how well observers utilize cues to consonant identification from different spectral regions that occur asynchronously as opposed to synchronously across frequency; such an ability would be useful for processing speech in the context of a spectro-temporally complex masker (e.g., competing speech). This was assessed by obtaining masked identification thresholds for VCV speech material, of the form /a/ C /a/, under various conditions of 10-Hz or 20-Hz square-wave amplitude modulation (AM). The speech tokens were filtered into 2, 4, 8, or 16 contiguous log-spaced frequency bands spanning 0.1 to 10 kHz. Bands were then modulated, with the pattern of that AM being either coherent across bands or 180 degrees out of phase for adjacent bands. In the out-of-phase conditions the odd-numbered bands had coherent phase AM and the even bands had coherent phase AM, but the AM pattern across these two subsets of bands were out of phase. Results from these two conditions, along with further conditions employing only modulated even- or odd-numbered bands, allowed performance to be compared between stimuli characterized by synchronous and asynchronous cues. Results indicate that observers are able to utilize asynchronously presented cues to consonant identification efficiently across a range of conditions.

Acoustic Stimulation↗

PubMed2003

The effect of otitis media with effusion on perceptual masking.

OBJECTIVE: To determine the effect of otitis media with effusion (OME) on perceptual masking (a phenomenon in which spondee threshold for a 2-talker masker is poorer than for a speech-shaped noise masker). DESIGN: Longitudinal testing over a 1-year period following insertion of tympanostomy tubes, using clinical and normal-hearing control groups. SUBJECTS: Forty-seven children having a history of OME were tested. Possible testing intervals were just before the placement of tympanostomy tubes, and up to 3 separate occasions after the placement of the tubes. An age-matched control group of 19 children was tested. METHODS: A perceptual masking paradigm was used to measure the ability of the listener to recognize a spondee in either a speech-shaped noise or a 2-talker masker background. The masker was either continuous or gated on and off with the target spondee. RESULTS: In gated masking conditions, children with a history of normal hearing showed only slight perceptual masking, but the children with a history of OME showed relatively great perceptual masking before surgery and up to 6 months following surgery. In continuous masking conditions, both groups of children showed relatively great perceptual masking and did not differ significantly from each other in this respect either before or after surgery. However, before surgery, the OME group showed higher thresholds in both the 2-talker and speech-shaped noise maskers. CONCLUSIONS: In agreement with previous psychoacoustical findings, the relatively great perceptual masking in gated conditions shown by children with OME history may reflect a general deficit in complex auditory processing.

Age Factors↗

PubMed2003

Effect of amplitude modulation coherence for masked speech signals filtered into narrow bands.

Introduction of masker amplitude modulation (AM) can improve signal detection in a number of paradigms. In some cases this advantage depends on the coherence of modulation across a relatively wide frequency range. In the experiments described below, observers were asked to identify masked spondee words produced by a single male talker. The target spondees and masking noise were filtered into nine narrow bands, and the coherence of AM of either the speech signal or noise masker was manipulated. Inherent modulation of the masker bands was manipulated via assignment of real and imaginary values to the associated components of each band in the frequency domain, and AM of speech bands was achieved via multiplication with envelopes extracted from these maskers. Responses were based on two alternatives, four alternatives, or open response sets. The effect of masker AM coherence was highly dependent upon the size of the response set: coherent AM was associated with better thresholds in a two-alternative response set, but poorer thresholds in an open response set. Results with AM speech did not depend critically upon the across-frequency temporal synchrony of AM imposed on the speech material.

Adult↗

PubMed2003

Modulation rate discrimination for unresolved components: temporal cues related to fine structure and envelope.

The present study investigated the hypothesis that the cues for modulation rate discrimination for unresolved spectral components differ as a function of the spectral region occupied by the stimuli. Specifically, it was hypothesized that when components occupy relatively low spectral regions, phase locking both to the fine structure and to the envelope are useful cues. However, as the spectral region occupied by the components increases, phase locking to the fine structure becomes less robust, whereas phase locking to the envelope remains as a potentially strong cue. Observers were asked to detect a decrease in modulation rate for carrier frequencies between 1500 and 6000 Hz. Both amplitude-modulated (AM) and quasifrequency-modulated (QFM) tones were used in order to produce stimuli having strong and weak envelope cues, respectively. Although there were marked individual differences, the results showed an interaction between modulation type and spectral region, with AM and QFM performance being relatively similar at low spectral region, but with QFM showing a steeper reduction in performance as the spectral region of the carrier frequency increased. Overall, the data are consistent with an interpretation that pitch perception for unresolved components depends upon both fine structure and envelope cues, and that the relative importance of these cues depends upon the spectral region occupied by the stimuli.

Adult↗

PubMed2003

The masking level difference for signals placed in masker envelope minima and maxima.

Previous data on the masking level difference (MLD) have suggested that NoSpi detection for a long-duration signal is dominated by signal energy occurring in masker envelope minima. This finding was expanded upon using a brief 500-Hz tonal signal that coincided with either the envelope maximum or minimum of a narrow-band Gaussian noise masker centered at 500 Hz, and data were collected at a range of masker levels. Experiment 1 employed a typical MLD stimulus, consisting of a 30-ms signal and a 50-Hz-wide masker with abrupt spectral edges, and experiment 2 used stimuli generated to eliminate possible spectral cues. Results were quite similar for the two types of stimuli. At the highest masker level the MLD for signals coinciding with masker envelope minima was substantially larger than that for signals coinciding with envelope maxima, a result that was primarily due to decreased NoSpi thresholds in masker minima. For most observers this effect was greatly reduced or eliminated at the lowest masker level. These level effects are broadly consistent with the presence of physiological background noise and with a level-dependent binaural temporal window. Comparison of these results with predictions of a published model suggest that basilar-membrane compression alone does not account for this level effect.

Acoustic Stimulation↗

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↗