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Biomedical subjects

J W Hall

Publications and source records attributed to J W Hall.

At least 73 records · Page 4Linked to original sources
PubMed1995

Amplitude discrimination in masking release paradigms.

In the first phase of the study, detection thresholds were obtained in conditions that were associated with comodulation masking release (CMR), conditions that were associated with the masking-level difference (MLD), or conditions that were not associated with masking release (baseline conditions). In the second phase of the study, amplitude discrimination was determined for standard tones presented at sensation levels (SLs) 0-30 dB above the masked detection thresholds. Results indicated that, at matched SLs, amplitude discrimination was poorer under conditions of masking release than for baseline conditions, both for the MLD and for CMR. Implications of these results for models of masking release are discussed.

Adult↗
PubMed1995

Pasture management strategies for reducing the risk of legume bloat in cattle.

Results from two decades (1973-1993) of bloat research at Kamloops are reviewed. The trials were conducted with groups of ruminally fistulated cattle either grazing or fed daily fresh-cut alfalfa (Medicago sativa) herbage. Studies were conducted during the growing season (May to September) and in the fall (October and November). The alfalfa was usually in the vegetative to early bloom stages of growth. Visual assessments of bloat severity on a scale of 1 to 5 were made .5 to 2 h after feeding started, at which time ruminal cannulas were opened to relieve ruminal pressure. Every cultivar of alfalfa tested caused bloat, but sainfoin (Onobrychis viciifolia), birdsfoot trefoil (Lotus corniculatus), and cicer milkvetch (Astragalus cicer) did not. This confirms the bloat-safe features of these alternate legume forages. Bloat was positively associated with the level of Fraction 1 protein and total soluble protein in alfalfa, supporting the concept of a decreased probability of bloat with advancing stages of plant maturity. There was no association between alfalfa saponins and bloat. Prefeeding ruminal chlorophyll levels were higher and ruminal clearance rates were lower in cattle that were susceptible to bloat. Cattle that bloated on a given day consumed 18 to 25% less alfalfa immediately before bloat than non-bloaters did in the same time period. Ruminal cations were associated with bloat incidence but cation manipulation through supplementation did not prevent bloat. Of all the feed additives tested, only poloxalene (Bloat Guard) completely prevented bloat.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1995

Auditory dysfunction in selected syndromes and patterns of malformations: review and case findings.

Hundreds of syndromes may be associated with hearing impairment. Within recent years, there has been heightened research and clinical interest in hearing and syndromes, probably due to both advances in molecular genetics and improved techniques for auditory assessment of infants and young children. An example of the current appreciation for the possible relation between auditory dysfunction and syndromes or patterns of malformations is the inclusion of syndromes as a risk factor for hearing impairment by the 1990 Joint Committee on Infant Hearing. In this paper, we review syndromes and patterns of malformation that are frequently or occasionally associated with hearing impairment. In addition, we illustrate, in case studies, auditory findings that may be associated with three of these syndromes and patterns of malformation: Carpenter syndrome, ichthyosiform dermatosis, and Townes syndrome. We conclude with a discussion of strategies for audiologic assessment and management of infants and children with syndromes and patterns of malformations.

Adolescent↗
PubMed1994

Modulation Detection Interference (MDI) in listeners with cochlear hearing loss.

This study compared Modulation Detection Interference (MDI) in listeners with cochlear hearing loss and in listeners with normal hearing. The study was motivated by questions of temporal resolution in the listeners with cochlear hearing loss as well as by their general difficulty in monitoring target sounds in the presence of competing background noise. The first experiment was similar to the MDI paradigm of Yost and Sheft (1989) and showed an equivalence in performance between the two groups of listeners: MDI brought about by an interfering tone comodulated with the target tone at 10 Hz was about 11 dB in both groups. There was also no difference in MDI magnitude when the modulation rate of the interferer changed to 25 Hz, indicating a lack of tuning to differential modulation rate in the gated paradigm employed here. The second experiment was analogous in concept to the measurement of a psychophysical tuning curve; the depth of modulation of the interfering carrier was adjusted to just interfere with the detection of a suprathreshold degree of modulation on the target carrier. The listeners with cochlear hearing loss performed quite similarly to the normal group, and the general lack of a frequency effect for the carrier tones suggested that MDI was relatively insensitive to presumed differences in auditory filter bandwidth between listeners. Because the basis of MDI has been hypothesized to be the fusion of the interfering tone with the target tone, the results of this study suggest that the auditory grouping factors presumed to underlie MDI are intact in listeners with hearing loss of cochlear origin.

Acoustic Stimulation↗
PubMed1994

Effect of otitis media with effusion on comodulation masking release in children.

This study investigated comodulation masking release (CMR) in a group of children with a history of otitis media with effusion (OME) and a control group of children with no known history of ear disease. CMR was measured both in a monotic condition and in a dichotic condition (where comodulated flanking bands were added to the ear contralateral to the signal). CMR was measured before the insertion of pressure equalization tubes, approximately 1 to 3 months after surgery, and approximately 6 to 8 months after surgery. The results indicated that monotic CMRs were reduced in children who had hearing loss due to OME. Furthermore, the monotic CMR remained abnormally small even when threshold had returned to normal for 1 to 3 months. The monotic CMR was essentially normal 6 to 8 months following surgery. No differences were found between the two groups of children for the dichotic CMR.

Age Factors↗
PubMed1994

Motivation and methods for manipulating acoustic ringing of earphones.

Transient acoustic stimuli are used for generating auditory evoked responses (AERs). Common transducers do not accurately reproduce transient stimuli, since the transducer diaphragm oscillates at its resonant frequency at the abrupt initiation or termination of a stimulus. These oscillations are called "acoustic ringing." This paper discusses methods for reducing and canceling acoustic ringing, and describes one method, a systems approach, in detail. It also delineates one method for enhancing acoustic ringing. The methods described provide effective techniques for empirical study of the effects of acoustic ringing on AERs or for any application requiring accurate transduction of a transient stimulus.

Acoustics↗
PubMed1994

Signal detection in complex comodulated backgrounds by normal-hearing and cochlear-impaired listeners.

Comodulation masking release (CMR) was investigated in normal-hearing and cochlear-impaired listeners. The narrow-band masker centered on the tonal signal was flanked by a series of other narrow noise bands, some of which had temporal envelopes that were the same as that of the on-signal band (comodulated bands) and some of which had different temporal envelopes (codeviant bands). Previous research using such stimuli with normal-hearing listeners indicated that CMR was often substantially reduced when two codeviant bands were present at spectral locations close to the signal frequency, but that CMR recovered to some extent when more codeviant bands were added. In the present study, cochlear-impaired listeners showed an abnormally large reduction in CMR when codeviant bands were present, and poorer recovery of CMR with increasing number of codeviant bands. Supplementary experiments suggested that the poor recovery of CMR with increasing number of codeviant bands may have been due to the small range (in dB) over which CMR could occur in cochlear-impaired listeners. It is possible that abnormal reduction in CMR with codeviant bands present was due to poor peripheral analysis in hearing-impaired listeners.

Acoustic Stimulation↗
PubMed1994

The effect of conductive hearing loss on the masking-level difference: insert versus standard earphones.

Previous studies have indicated that the masking-level difference is reduced in listeners having conductive hearing loss, even when sensation level is controlled. According to the crosstalk hypothesis, this deficit can be explained in terms of reduced binaural cues at the level of the cochleas, due to acoustic contributions from the bone conduction route. It is possible that such a deficit can be overcome through the use of insert earphones, because such transducers provide a high degree of interaural attenuation. In this study, NoSo and NoS tau thresholds were measured in normal-hearing subjects and in subjects having hearing loss due to otosclerosis, using both standard TDH earphones encased in NAF-48490-1 circumaural cushions and deeply seated Etymotic 3A insert earphones. Masking noise was presented both at a fixed sound-pressure level and at a fixed sensation level. The results did not indicate consistently larger MLDs with insert earphones for either group of subjects, for either type of presentation level. The MLDs of the hearing-impaired subjects often remained abnormally small even when the insert transducers were used and the noise was presented at a fixed SL. Whereas acoustic crosstalk appeared to have a role in the results obtained, other factors (perhaps related to long-term hearing threshold asymmetry and/or interaural phase mismatch) also were apparently involved.

Acoustic Impedance Tests↗
PubMed1994

Development of temporal resolution in children as measured by the temporal modulation transfer function.

Temporal modulation transfer functions (TMTFs) were measured in listeners aged 4 years to adult in order to characterize the development of temporal resolution in children. Four age groups were tested, 4-5 years of age, 6-7 years of age, 9-10 years of age, and adult. Sensitivity to sinuosoidal modulation of a noise carrier (a bandpass noise from 200-1200 Hz) was determined for modulation frequencies of 5, 20, 100, 150, and 200 Hz. The data from all listeners indicated decreasing sensitivity to modulation as a function of increasing frequency of modulation. Time constants were derived from the 3-dB down points of functions that were fitted to the data. No age effects were observed for the derived time constants. However, sensitivity to modulation was found to be reduced in the children 4-5 and 6-7 years of age, as compared to adults, and in the children 4-5 years of age as compared to children 9-10 years of age. The agreement of time constant across all age groups was interpreted as indicating that the peripheral encoding of the temporal envelope is probably adultlike in children aged 4 years and above; however, young children appear to be relatively inefficient in processing the information underlying modulation detection.

Acoustic Stimulation↗
PubMed1994

Comodulation masking release for elderly listeners with relatively normal audiograms.

Thresholds for the detection of a 1.0-kHz pure tone were measured in modulated and unmodulated noise for a group of nine elderly listeners, aged 62-83, with normal or near-normal audiograms, and a reference group of seven younger normal-hearing listeners. The masker was either a band of noise 128 Hz wide [approximately one equivalent rectangular bandwidth (ERB) centered at 1.0 kHz], or a band of noise 1505 Hz wide (approximately five ERBs above and five ERBs below 1.0 kHz). The noise was either unmodulated or was square-wave modulated at rates of 10, 20, 30, 40, and 50 Hz. A measure of comodulation masking release (CMR) was derived from the masking data. Because wider filters have been found to be associated with reduced CMR, auditory filter shapes were also estimated for the elderly listeners. The filters were found to be normal at the center frequencies of 800, 1000, and 2000 Hz ruling out possible confounding effects of impaired auditory filters on CMR. Masked detection thresholds were generally significantly higher for the elderly as compared to the younger listeners for both unmodulated and modulated noise. Thresholds were lower in modulated as compared to unmodulated noise masking for both elderly and young listeners. For both groups of listeners and for both narrow- and wideband masking, detection thresholds continued to increase as modulation rates were increased. CMR was not different for the elderly and young listeners and it was similarly decreased, for both groups, at higher rates of modulation.

Adult↗
PubMed1994

Clinical application of otoacoustic emissions: what do we know about factors influencing measurement and analysis?

Three electrophysiologic audiologic procedures-aural immittance measurement, auditory brainstem response (ABR), and otoacoustic emissions (OAE)- were first described in the 1970's. Immittance measurement and ABR have contributed importantly for years to the assessment of auditory function in children and adults, whereas OAEs have not yet been incorporated into the everyday audiology test battery. In this article, we argue that the transition from OAE measurement by hearing scientists in laboratory settings to routine application by audiologists in the clinic will be greatly facilitated by (1) comprehensive, large-scale studies of the effects of subject characteristics, such as gender and age (from infancy to advancing adulthood), on both transient evoked (TEOAE) and distortion product (DPOAE) otoacoustic emissions; (2) clinical investigations of TEOAE and DPOAE in sizeable patient populations with specific neurotologic diagnoses; (3) guidelines for OAE test protocols in clinical environments; and (4) clear criteria for OAE analysis in clinical populations.

Acoustic Stimulation↗
PubMed1994

Evaluation of two supplements for the prevention of alfalfa bloat.

Poloxalene and a mineral mixture feed supplement patented for the treatment of emphysema, polyarthritis, and other pectin related diseases were tested in two trials for their ability to prevent bloat in cattle fed fresh alfalfa. Each trial had a crossover design using three Jersey steers with rumen fistulas per group. Each trial period continued until the total number of cases of bloat reached > or = 24. Treatments were given at 0800 each day. The mineral mixture was given at 100 g/d and 190 mg/kg body weight per day in the first and second trials, respectively. Poloxalene, which was tested only in the second trial, was given at 23 mg/kg body weight per day. Each group of steers was then fed 200 kg of freshly harvested alfalfa in the vegetative to early bloom stages of growth at 0830. In the first trial, only 69% as many cases of bloat occurred on the mineral mixture as on the control treatment, but no significant difference was detected in the second trial. The potency of the alfalfa may have been higher in the second trial, when forage dry matter was lower, magnesium and soluble nitrogen were higher, and bloat occasionally occurred twice a day. Bloat did not occur when the steers were treated with poloxalene. In these trials, poloxalene was completely effective in preventing bloat, but the mineral mixture was only partially so.

Animal Feed↗
PubMed1993

Invited commentary: cryopreservation as a tool for the study of selectively bred lines in rodent behavioral genetics.

Cryopreserved embryos should survive centuries. Upon rederivation, in vitro survival is high. Upon reimplantation, in vivo survival is substantial. Genetic stability of the embryos at -196 degrees C is theoretically absolute for several decades and likely high for centuries. Cryopreservation and rederivation services are available at a reasonable cost from commercial vendors. Preservation of a sufficient number of embryos can serve as an insurance policy against loss of the lines from several causes. In addition to the protective utility of a single banked sample, repeated preservation during the course of selection offers several advantages. Correlated responses to selection which appear late in selection may be verified by use of a cross-sectional experimental design to take a "snapshot" of the gradually developing response. After attainment of the selection limit, a generation may be chosen retrospectively which represents the best compromise between maximizing response and minimizing inbreeding irrelevant to the selected trait. Estimates of changes in gene frequencies could be derived from molecular biological analyses. An example of such an experiment in progress employing embryos from the COLD and HOT selected mouse lines is discussed.

Animals↗