Biomedical subjects

J W Hall

Publications and source records attributed to J W Hall.

At least 55 records · Page 3Linked to original sources

PubMed1996

Perceptual organization of sequential stimuli in listeners with cochlear hearing loss.

The perceptual organization of sequential stimuli presumably depends in part on the fidelity with which acoustic cues are encoded in the auditory system. The purpose of this study was to examine the effects of cochlear hearing loss on two measures of sequential processing that rely on spectro-temporal information. The results of a gap detection/discrimination task indicated that listeners with cochlear hearing loss exhibited particular difficulty discriminating gaps between tonal markers that were disparate in frequency. Performance improved when the disparate tones were embedded into a sequence of alternating low- and high-frequency tones that may have facilitated the perceptual of the stimuli into separate auditory streams. However, performance for listeners with cochlear hearing loss was generally poorer than that of normal-hearing listeners and did not appear to be related to threshold in quiet or to frequency selectivity. The results of a melody recognition task that required a target melody to be "heard out" from simultaneous competing melodies also indicated generally poorer performance on the part of the listeners with hearing loss, although the pattern of results across all listeners was highly idiosyncratic. It was concluded that cochlear hearing loss deleteriously affects the processes underlying perceptual organization of sequential stimuli. In particular, perceptual organization in the presence of cochlear hearing loss appears to require a greater frequency separation between presumed auditory streams in comparison to normal-hearing listeners.

Adult↗

PubMed1996

Are the palmar cutaneous nerves safe during standard carpal tunnel release?

An incision in the axis of the ring finger is thought to be the safest for carpal tunnel release based on cadaveric studies that suggest that the palmar cutaneous nerves do not cross into this area. Despite the use of this incision, persistent postoperative scar tenderness has been reported in up to 36% of patients following standard carpal tunnel release. For this reason, an investigation was undertaken to determine the presence of palmar cutaneous nerves in this incision. Random biopsies of transversely oriented fibrous bands in the subcutaneous tissue were taken during 15 open carpal tunnel releases. In every patient, at least one biopsy was positive for peripheral nerve tissue. These findings, combined with previous cadaveric studies, suggest that a "safe" palmar incision that will avoid injury to palmar cutaneous nerves does not exist. Carpal tunnel release techniques that avoid a palmar incision may lessen postoperative morbidity by avoiding injury to these small cutaneous nerves.

Carpal Bones↗

PubMed1996

Is training in endoscopic carpal tunnel release appropriate for residents?

Based on the relatively high incidence of complications for surgeons initially learning the technique, endoscopic carpal tunnel release is thought to have a steep learning curve. To determine if endoscopic carpal tunnel release can be safely performed by trainees, the outcomes of 84 patients who underwent endoscopic carpal tunnel release performed by a chief resident or hand fellow in a supervised setting were reviewed. All but 1 patient had uneventful procedures and complete resolution of preoperative symptoms. One patient with persistent symptoms represented the only complication. At reexploration through a standard palmar incision, the transverse carpal ligament was found to have been completely divided and fulminant tenosynovitis surrounding the nerve and flexor tendons was presumed to be the cause of his persistent symptoms. It appears that endoscopic carpal tunnel release can be safely performed by chief residents in a supervised clinical setting. Given that this procedure has a high learning curve, repeated exposure during a residency training program may offer significant advantages over the current approach of training surgeons during a single cadaveric instructional course.

Cadaver↗

PubMed1996

Gap detection for pairs of noise bands: effects of stimulus level and frequency separation.

Temporal gap detection was determined for single 20-Hz-wide noise bands having various center frequencies, and for simultaneously present pairs of noise bands where the spectral separation between center frequencies was varied. in most conditions, each noise band was present 30 dB above its detection threshold, but in some conditions, each noise band was presented 15 dB above its detection threshold. The results for single noise bands indicated that the gap threshold did not vary significantly across center frequency. Gap detection was significantly better for pairs of noise bands than for single noise bands. The improvement in gap detection when two noise bands were presented instead of one was greater at the 15-dB presentation level than at the 30-dB level. In the case where pairs of bands were presented, there was no effect of the spectral separation between bands, even though the spectral separation was varied over a range of 5 oct. Spectral integration for gap detection may be limited only by the audibility curve.

Adult↗

PubMed1996

Across-frequency processing of multiple modulation patterns.

This study sought to determine the degree to which the auditory system can perform simultaneous across-frequency analyses on concurrent, but independent, modulation patterns. This was tested by measuring detection of a multicomponent signal presented against a background comprised of multiple modulation patterns. The results indicated that independent comodulation masking releases (CMRs) could occur simultaneously, but only if the independent modulation patterns were restricted to relatively discrete frequency regions. Moreover, the analysis accomplished in each region did not appear to be optimal. This suggests that there are limits to the independence with which simultaneous across-frequency analyses can be performed.

Adult↗

PubMed1996

Cochlear hearing loss and the processing of modulation: effects of temporal asynchrony.

Temporal coincidence and envelope correlation among components of a complex sound are informative cues for the perceptual organization of that sound. Listeners with hearing loss of cochlear origin often exhibit reductions in temporal processing of stimuli with randomly fluctuating envelopes. The purpose of this study was to examine the performance of such listeners on auditory grouping tasks which rely on temporal cues. The first experiment examined temporal asynchrony effects in a comodulation masking release (CMR) task. Performance was poorer than normal and appeared to be associated with reduced frequency selectivity. However, the pattern of asynchrony effects was the same as normal. The second experiment examined temporal asynchrony effects in a task based on envelope comparison interference. On this task, performance was similar to that for normal-hearing listeners. It was concluded that listeners with hearing loss of cochlear origin are comparable to normal-hearing listeners in their ability to make use of relatively gross temporal asynchrony cues.

Adult↗

PubMed1996

Effects of masker gating for signal detection in unmodulated and modulated bandlimited noise.

Thresholds for a 400-ms 1000-Hz pure-tone signal were obtained as a function of masking noise bandwidth for unmodulated and square wave modulated masking noise. Rates of modulation were 10 and 40 Hz. Noise bandwidths were 128 Hz, 387 Hz, 921 Hz, and 1505 Hz. The masking noise was either continuous or gated on and off with the signal. In general, signal thresholds were relatively constant as a function of noise bandwidth in unmodulated noise, and improved as a function of increasing noise bandwidth in modulated noise. Noise gating had little or no effect on signal threshold in unmodulated noise. At the 10-Hz modulation rate, signal thresholds were somewhat higher in gated than in continuous noise at relatively narrow noise bandwidths, but thresholds were similar in gated and continuous noise for relatively wide noise bandwidths. At bandwidths of 387, 921, and 1505 Hz, comodulation masking release (CMR) was calculated as the unmodulated noise threshold minus the modulated noise threshold, corrected by the difference between the unmodulated noise threshold and the modulated noise threshold at the 128-Hz bandwidths. At wide masker bandwidth, CMRs were higher for gated noise than for continuous noise. This was due almost entirely to the threshold gating effect found in the 128-Hz bandwidth condition. These results suggested that there was a within-channel effect for gated noise thresholds to be higher than continuous noise thresholds, but essentially no across-channel effect of gating. At the 40-Hz modulation rate, signal thresholds were similar for gated and continuous noise at all noise bandwidths. There was a very small but significant' effect for the gated noise threshold to be lower than the continuous noise threshold at the widest noise bandwidth. It was speculated that this effect may be related to a decrease in sensitivity to modulation with continuous stimulation. In general, effects of gating appear to be small or absent for across-channel masking release in broadband modulated masking noise.

Adult↗

PubMed1996

Evaluation of clinicopathological parameters in cattle grazing timber milkvetch.

The purpose of this study was to determine whether hematological and serum biochemical parameters could be used to diagnose poisoning in cattle grazing timber milkvetch (Astragalus miser var. serotinus), a nitropropanol-containing legume. Blood samples were obtained from 20 Hereford cattle on timber milkvetch range in southern British Columbia during 1992 and 1993. Relevant changes in blood parameters were not detected and the parameters could not be used to predict nitropropanol ingestion or intoxication. The same parameters were measured in dosing trials with cattle with rumen fistulas, but relevant changes were not detected. Succinate dehydrogenase is the key target in nitropropanol intoxication and an assay for this enzyme may provide a probe for diagnosis.

Animals↗

PubMed1996

Evidence against the influence of aging on distortion-product otoacoustic emissions.

Previous research has reported reduced otoacoustic emission amplitude as a function of age. In each study, however, interpretation of findings was confounded by age-related hearing loss. The present study was designed to re-evaluate the contribution of age and peripheral hearing loss on the prevalence and amplitude of distortion-product otoacoustic emissions (DPOAEs) by controlling for degree of peripheral hearing loss. Twenty subjects were divided into four age ranges. All subjects in each group had 15 dB HL or better thresholds from 0.25 through 8 kHz and normal immittance findings. DPOAE audiograms recorded at three intensity levels and input/output functions recorded at six discrete frequencies showed no significant differences in amplitude or noise level between age groups. Findings indicate that when the degree of peripheral hearing loss is adequately controlled, there is no direct effect of advanced age on DPOAE measures. Clinical implications are discussed.

Acoustic Stimulation↗

PubMed1995

Long-term effects of chronic otitis media on binaural hearing in children.

OBJECTIVE: To determine the long-term effect of otitis media with effusion (OME) on binaural hearing in children. DESIGN: Longitudinal testing over a 4-year period following insertion of tympanic membrane grommets, employing clinical and normal control groups. SUBJECTS: Twenty-two children with a history of OME were tested before insertion of grommets and at 3 months and 1 year after surgery; 14, 11, and 8 of the children were followed up for 2, 3, and 4 years after surgery, respectively. An age-matched control group of 40 children was tested. METHODS: The masking-level difference (MLD) paradigm was used to measure the ability of the binaural auditory system to aid the detection of a pure-tone signal presented in a random masking noise. RESULTS: Although the results indicated a significant improvement in the MLD with increasing time after middle ear surgery, the MLD remained significantly reduced even 2 years after hearing threshold correction. The MLDs of the OME group did not differ significantly from those of the control group when tested 3 years after middle ear surgery, even though a small proportion of subjects with a history of OME continued to have MLDs smaller than normal limits. CONCLUSIONS: In general, the results suggest a slow recovery of binaural function in children with OME after restoration of normal hearing thresholds.

Adolescent↗

PubMed1995

Binaural function in children with attention-deficit hyperactivity disorder.

OBJECTIVE: To evaluate the basic binaural function of children with attention-deficit hyperactivity disorder (ADHD). DESIGN: Case-control study. Measures of binaural function were compared for children with and without ADHD. SUBJECTS: Forty-two children; 26 had ADHD and 16 were normal controls. INTERVENTIONS: None. RESULTS: For detection tasks, no differences were seen between children with ADHD and controls. For speech recognition tasks, the younger children with ADHD did not perform as well as the controls. CONCLUSIONS: Younger children with ADHD might have a reduced processing efficiency for signal recognition in certain types of noise, but not for signal detection.

Adolescent↗

PubMed1995

Masker interaural phase and the MLD: effects of conductive hearing loss.

Sensitivity to binaural signals that were interaurally antiphasic with respect to the masking noise was examined as a function of the interaural phase of the masking noise, for listeners with normal hearing, and listeners with conductive hearing losses. Some of the hearing-impaired listeners were tested both before and after middle ear surgery. In agreement with previous findings, the normal-hearing listeners showed the lowest thresholds when the masking noise had no interaural phase shift, with thresholds increasing monotonically as the interaural phase of the center frequency of the masker approached +/- 180 degrees. Although many of the masked threshold functions of the hearing-impaired listeners showed significant changes in thresholds as a function of masker interaural phase, most of the functions were abnormal in shape, and few showed peaks for the interaural masker phase of 0 degrees. Although functions often continued to be abnormal after middle ear surgery, a few subjects obtained postsurgery functions that were correlated with the average normal function. The results indicate that although normal-hearing listeners generally have the lowest antiphasic signal threshold for a masker with 0 degrees interaural phase, conductively-impaired listeners often do not show a clear minimum for antiphasic signal threshold at any particular masker interaural phase.

Acoustic Stimulation↗

PubMed1995

A gene for autosomal dominant nonsyndromic hereditary hearing impairment maps to 4p16.3.

Mapping genes for nonsyndromic hereditary hearing impairment may lead to identification of genes that are essential for the development and preservation of hearing. We studied a family with autosomal dominant, progressive, low frequency sensorineural hearing loss. Linkage analysis employing microsatellite polymorphic markers revealed a fully linked marker (D4S126) at 4p16.3, a gene-rich region containing IT15, the gene for Huntington's disease (HD). For D4S126, the logarithm-of-odds (lod) score was 3.64 at theta = 0, and the overall maximum lod score was 5.05 at theta = 0.05 for D4S412. Analysis of recombinant individuals maps the disease gene to a 1.7 million base pair (Mb) region between D4S412 and D4S432. Genes for two types of mutant mice with abnormal cochleovestibular function, tilted (tlt) and Bronx waltzer (bv), have been mapped to the syntenic region of human 4p16.3 on mouse chromosome 5. Further studies with the goals of cloning a gene for autosomal nonsyndromic hearing impairment and identifying the murine homologue may explain the role of this gene in the development and function of the cochlea.

Adolescent↗

PubMed1995

Central auditory processing in Alzheimer's disease.

OBJECTIVE: This investigation was designed to determine whether people in the early to middle phases of Alzheimer's disease (AD) show impaired central auditory processing as compared with nondemented elderly. DESIGN: A peripheral and central auditory test battery was administered to 10 subjects diagnosed with mild-to-moderate AD based on a neuropsychological test battery and radiographic techniques, and a control group of 10 subjects with no evidence of dementia, matched for age, gender, and average degree of hearing loss. Immittance audiometry, pure-tone and speech audiometry, and otoacoustic emissions were recorded in all subjects. Central auditory assessment included the synthetic sentence identification with ipsilateral competing message, dichotic digits, dichotic sentence identification, pitch patterns, and duration patterns. RESULTS: Peripheral auditory status was statistically similar between subject groups. Neither average high frequency hearing sensitivity nor mean speech recognition ability was significantly different. However, a significant difference was noted between groups for average low frequency hearing sensitivity in the left ear (p < 0.05). Subjects with AD showed slightly poorer low frequency thresholds versus matched controls. Based on analysis of performance on each measure of the central auditory test battery, the AD group scored significantly lower than the matched control group on four of the five measures utilized. Differences for right versus left ear performance were found among AD subjects. CONCLUSIONS: Overall patterns in findings cannot be easily explained as artifacts of cognitive decline. Results support screening for central auditory dysfunction in the AD population, since impaired processing could influence psychiatric assessment of cognitive deficit as well as audiologic management of peripheral hearing loss in this population.

Aged↗

PubMed1995

Comodulation masking release (CMR): effects of gating as a function of number of flanking bands and masker bandwidth.

Normal-hearing subjects participated in two CMR experiments. For experiment 1, two, three, five or nine 20-Hz-wide comodulated flanking bands were presented continuously or gated simultaneously with a 2000-Hz signal. The signal had a duration of 400 ms. Larger CMRs were obtained as the number of flanking bands increased for both the continuous and gated conditions. For fewer number of bands, the average CMR for continuous noise was substantially larger than for gated noise. As the number of bands increased, CMR increased more for gated than for continuous noise, and the difference between CMRs for gated and continuous noise decreased. Experiment 2 involved detecting a 400-ms 1000-Hz pure-tone signal in a seven-band comodulated noise complex. The noise bands, presented continuously or gated with the signal, were either 10, 20, 40, or 80 Hz wide. Larger CMRs were observed for continuous maskers and for smaller masker bandwidths; however, the effect of gating did not change significantly across bandwidth. The results of the first experiment indicate that the effects of gating on CMR are minimized when the number of auditory channels providing information is large. The results of the second experiment indicate that this effect is not simply a function of the large CMR magnitude obtained with a large number of flanking bands.

Adult↗

PubMed1995

Modulation detection interference using random and sinusoidal amplitude modulation.

The detection of amplitude modulation (AM) of a target sound is made more difficult by the presence of a modulated sound some spectral distance from the target. This effect (modulation detection interference, or MDI) was examined for stimuli with random amplitude modulations (RAM) and for sounds with sinusoidal amplitude modulations (SAM) as a function of average modulation depth (m) of the interferer. In an experiment comparing comodulated and independent RAM targets and interferers, the amount of interference was not related to the modulation coherence of the target and interferer. Elevations in AM threshold increased as a function of m in a similar way for both conditions. The MDI for RAM and SAM targets and interferers was also compared. While no difference was found for AM detection of RAM and SAM, MDI was found to be greater for the RAM stimuli than for the SAM stimuli. A subsidiary experiment comparing RAM and SAM modulation depth discrimination indicated that RAM discrimination is more difficult than SAM discrimination. Taken together, these results are quantitatively consistent with a mechanism resembling AM discrimination as the underpinning of MDI in conditions where the target and interferer are synchronously gated.

Adult↗

PubMed1995

Perceptual organization in a comodulation masking release interference paradigm: exploring the role of amplitude modulation, frequency modulation, and harmonicity.

Two areas of interest within auditory scene analysis are the identification of cues which contribute to auditory grouping and/or segregation, and the methodology employed to measure such effects. The present study explored the roles of three purported grouping cues--correlated AM, correlated FM, and harmonicity--using a comodulation masking release interference paradigm. This method was reasoned to be free of alterations in the subject's mode of listening (analytic versus synthetic). The results suggested that correlated AM was a viable grouping cue. For some listeners, the presence of FM also appeared to provide a grouping cue, but, generally, no effect of coherence of FM was observed. No effect of harmonicity was observed in this paradigm.

Adult↗

PubMed1995

Within- and across-channel processes in modulation detection interference.

Modulation detection interference (MDI) describes the effect of an amplitude-modulated sound on detection of amplitude modulation (AM) on a spectrally distant target sound. In MDI, AM detection is worsened by an AM interfering sound. Previous research has implicated both within-channel and across-channel processes as the basis for MDI. This study examined the detection of 10-Hz sinusoidal AM as a function of the spectral relationship, gating synchrony, and ear of presentation of the target and interfering sounds. Using a 993-Hz target sound, AM detection improved as the frequency of the interferer increased from 1250 to 2188 Hz, and as it decreased from 788 to 450 Hz. MDI was less for continuous interferers than for interferers gated synchronously with the target. In the continuous interferer conditions, however, MDI was still greatest for interferers most proximal to the target. The effects of frequency proximity and gating asynchrony were also evident using interferers presented to the ear contralateral to the target ear. While a 1250-Hz interferer led to more MDI than a 788-Hz interferer when the interferers were presented to the same ear as a 993-Hz target, no significant asymmetry was noted with dichotic stimulation. Taken together, the results of these experiments indicated that MDI is the result of across-channel, and to a limited extent, within-channel processes.

Adult↗