Biomedical subjects

J W Hall

Publications and source records attributed to J W Hall.

At least 37 records · Page 2Linked to original sources

PubMed1998

Perceptual consequences of peripheral hearing loss: do edge effects exist for abrupt cochlear lesions?

There is a growing body of research that shows evidence of central neural reorganization in response to lesions in the auditory periphery, even if the lesions occur in maturity. This reorganization consists of an increased neural representation of frequencies corresponding to the edge frequency of the lesion. Data were collected to determine whether this over-representation might have consequences for human perception. The hypothesis was that increased central representation might increase acuity on some psychophysical tasks performed at the edge frequency. Tasks included frequency sweep detection (for tones), intensity discrimination (for 100-Hz-wide bands of noise and tones), gap detection and gap discrimination (both for 100-Hz-wide bands of noise). Results from observers with steeply sloping hearing losses were compared with results from normal-hearing observers performing these tasks with masking noise generated to simulate steeply sloping hearing loss. None of these data provide compelling evidence for the hypothesized edge effect. A 40-Hz following response to tone bursts was collected from a subset of the hearing-impaired observers in an attempt to confirm the animal physiology findings of neural over-representation of the edge frequency. No edge-frequency effect was noted in the results, though there was a non-significant tendency for one of the hearing-impaired observers to show shorter latency of response.

Acoustic Stimulation↗

PubMed1998

Temporal analysis and stimulus fluctuation in listeners with normal and impaired hearing.

The first experiment investigated the effects of mild to moderate sensorineural hearing impairment on temporal analysis for noise stimuli of varying bandwidth. Tasks of temporal gap detection, amplitude modulation (AM) detection, and AM discrimination were examined. Relatively high levels of stimulation were used in order to reduce the possibility that the results of the listeners with hearing impairment would be influenced strongly by audibility. A general summary of results was that there was relatively great interlistener variation among the listeners with hearing impairment, with most listeners showing normal performance and some showing degraded performance, regardless of the bandwidth of the stimulus carrying the temporal information. A second experiment investigated the hypothesis that listeners with sensorineural hearing impairment might have poor gap detection due to loudness recruitment. Here, gap markers were presented at levels where loudness growth was steeper for the listeners with hearing impairment than for the listeners with normal hearing. Although gap detection was sometimes poorer in listeners with hearing impairment than in listeners with normal hearing, there was no clear relation between gap detection performance and loudness recruitment in listeners with mild to moderate sensorineural hearing impairment.

Acoustic Stimulation↗

PubMed1998

A broiler chick bioassay for measuring the feeding value of wheat and barley in complete diets.

Energy is an important component of poultry feed and is derived principally from cereal grains. Unfortunately, all of the chemical energy is not available to the bird, and biological assays must be used to determine the digestible energy value of a cereal grain. The bioassay described uses four pens of six male broiler chicks, complete diets containing 80% of a test cereal grain (with or without an appropriate commercial enzyme), and ad libitum feed intake. Apparent metabolizable energy values (kilocalories per kilogram of cereal grain, DM basis) values are calculated from gross energy and acid insoluble ash measurements of diet and excreta collected for 24 h at 16 d of age. To monitor variation between broiler chick assays, due to bird, environment, etc., common control samples of Hard Red Spring (HRS) and Canadian Prairie Spring (CPS) wheat were tested in each of 15 separate assays over 2 yr. Similarly, for barley, control samples of hulled and hulless barley were repeatedly tested in five assays. Broiler performance in this study was lower than expected for commercial broilers, in part due to a high dietary cereal grain component and the fine mash texture. However, AME values as determined were comparable to those reported in the literature for wheat and barley. The CV for AME measured among pens, representing the intra-assay CV, was between 1.2 and 3.4% and was lower with enzyme supplementation. The interassay CV was only slightly higher than the intra-assay CV. This assay provides precise estimations of ME in cereal grains fed to young broilers that can be used for diet formulation or for verification of laboratory measures of feeding value of cereal grains.

Animal Feed↗

PubMed1998

Using acid insoluble ash marker ratios (diet:digesta) to predict digestibility of wheat and barley metabolizable energy and nitrogen retention in broiler chicks.

Routine bioassay measurements of AME or N retention of broiler diets require measurements of gross energy (GE) or N and an acid insoluble ash marker in diet, excreta, or ileal digesta. These measurements of GE and N are time-consuming and expensive in comparison to measurements of added or natural occurring levels of acid insoluble ash. Data from bioassay measurements of AME and N retention of 138 wheat and 97 barley samples (with or without enzyme) were used to develop prediction equations relying on measurements of one that uses acid insoluble ash of diet, excreta or ileal digesta and GE and N of diet only; and a second equation using only acid insoluble ash of diet, excreta, or ileal digesta. The prediction equations demonstrate that part of or all of routine bomb calorimetry measurements for GE used to determine AME of wheat- or barley-based diets could be eliminated if a prediction error of 80 kcal/kg ME or less were acceptable. The prediction of N retention as compared to AME, based in part or totally on acid insoluble ash measurements, was less accurate; the prediction errors were equal to 2.3 and 6.5% for wheat- and barley-based diets, respectively. Ongoing research to improve the determination (speed, ease, and accuracy) of acid insoluble ash could provide a useful method to assess feeding value of ingredients and commercial poultry diets.

Animals↗

PubMed1998

The effect of masker interaural time delay on the masking level difference in children with history of normal hearing or history of otitis media with effusion.

OBJECTIVE: To determine the relation between the masking level difference (MLD) and the interaural time delay of the stimulus in children with a history of normal hearing and with a history of otitis media with effusion (OME). DESIGN: MLDs for a 500 Hz pure tone presented in a 100 Hz-wide masking noise were determined as a function of the interaural delay of the masker (six interaural delays between -726 microsec and +998 microsec were examined). For the masker with zero interaural delay, the signal was presented either interaurally in-phase or 180 degrees out of phase. For the masker delay conditions, the signal was given the same interaural delay as the masker and then was inverted interaurally. All children had normal audiograms at the time of testing. Ten children had a history of normal hearing and seven children had a history of OME. RESULTS: Similar to what has been found previously in adults, children with a history of normal hearing showed the maximum MLD (approximately 16 dB) for an interaural time delay of 0 microsec, with the MLD decreasing as a function of interaural time delay (by as much as 4 to 5 dB for the extreme delays). Children with a history of OME had significantly smaller MLDs than normal for the three smallest interaural delays but did not differ significantly from normal at the three largest interaural delays. CONCLUSIONS: The form of the function relating masker interaural time delay to MLD magnitude is adult-like by age 6 yr. The function indicates a binaural advantage for the processing of sound near auditory midline. This advantage is less apparent in children having a history of OME.

Audiometry, Pure-Tone↗

PubMed1998

Change in envelope beats as a possible cue in comodulation masking release (CMR).

The detection advantage associated with masker envelope coherence across frequency has typically been described in terms of comparisons of information across auditory channels. More recently it has been suggested that analysis of the output of a wider initial filter, similar to that suggested for the TMTF, can account for the data [B. G. Berg, J. Acoust. Soc. Am. 100, 1013-1023 (1996)]. This approach suggests that a change in envelope beats could serve as the cue to the addition of a pure-tone signal. Data are presented here for the detection of a tone added to multiple maskers with coherent envelopes. In one condition a change in envelope beats was an accurate potential cue, whereas in others the change was too unreliable to serve as an indicator of the presence of the signal. All conditions employing maskers with coherent envelopes produced very similar thresholds, and all showed improved sensitivity over the case of detecting a signal added to a single masker centered on the signal frequency. Results are interpreted as evidence that a change in envelope beats does not form the basis of detection in CMR.

Acoustic Stimulation↗

PubMed1998

The masking-level difference in low-noise noise.

In experiment 1 NoSo and NoS pi thresholds for a 500-Hz pure tone were obtained in a low-fluctuation masking noise and a high-fluctuation masking noise for six normal-hearing listeners. The noise bandwidth was 10 Hz. In agreement with previous investigations, the NoSo thresholds were lower in low-fluctuation noise than in high-fluctuation noise. For three listeners, NoS pi thresholds were similar for the two types of noise, while for the other three listeners, Nos pi thresholds were higher for low-fluctuation noise than for high-fluctuation noise. In experiment 2, the masker was created by amplitude modulating a 500-Hz pure tone by a 0-10-Hz low-pass noise. The degree of masker fluctuation was controlled by adjusting the average modulation depth (100%, 63%, 40%, and 25%). The signal was a 10-Hz-wide noise centered on 500 Hz. Results were similar to those of experiment 1: for the NoSo conditions, signal detection improved with decreasing degree of fluctuation, and for NoS pi conditions, the results were subject dependent. For three listeners, NoS pi thresholds were again similar in the two types of noise, while for the other three listeners, NoS pi thresholds were again higher in low-fluctuation noise than in high-fluctuation noise. The results showed that a high degree of masker fluctuation sometimes facilitates NoS pi detection. It is possible that the binaural detection mechanism utilizes the relatively good signal-to-noise ratios that occur in the low power or "dip" regions of fluctuating masker waveforms.

Adult↗

PubMed1998

Masker fluctuation and the masking-level difference.

Previous work suggests that, for some listeners, masker fluctuation may be advantageous for NoS pi detection. This study tested the hypothesis that the benefit of masker fluctuation to binaural analysis is based on the ability to take advantage of epochs of low masker energy in the fluctuating masker where the cues underlying binaural signal detection are more salient. The hypothesis was evaluated using the time-domain version of COSS analysis derived by Buus et al. [J. Acoust. Soc. Am. 99, 2288-2297 (1996)] which measures the perceptual weight applied by a listener within a relatively brief time window as a function of the masker level during the window. The results indicated a dependency of signal detection on short-term masker level in the NoS pi condition but not in the NoSo condition. This finding supports a new perspective indicating that binaural signal detection depends upon the envelope of a masker in a way that is fundamentally different from that typically associated with monaural detection.

Auditory Perception↗

PubMed1998

The role of auditory filters in comodulation masking release (CMR).

Comodulation masking release (CMR) is the detection advantage conferred by coherence of amplitude modulation across masker frequency. This phenomenon has typically been described in terms of across-frequency comparisons or in terms of cueing, where analysis of the output of an auditory filter in the region of the signal is aided by the outputs of independent auditory filters. An alternative approach is to assume a broad initial predetection filter, one which encompasses frequencies generally thought to fall into disparate auditory filters. These two basic approaches are compared. Stimuli consisted of comodulated maskers, spaced in frequency at one of three fixed intervals, with fine structure that either produced strong envelope beats in the summed waveform or did not. The signal was a pure tone of random starting phase. For the smallest masker frequency spacing detection of a high-frequency signal seemed to be improved in the presence of envelope beats, while detection of a low-frequency signal seemed to be degraded by envelope beats. These results are discussed in terms of the number of maskers assumed to sum in an auditory filter and the relative availability of within- and between-channel cues. This explanation is consistent with an initial stage of auditory filtering and is fundamentally inconsistent with a broad initial filter. Results for larger masker frequency spacings showed this trend less reliably, a finding that was further explored via data from a modulation discrimination task.

Adult↗

PubMed1997

Human offset auditory brainstem response: effects of stimulus acoustic ringing and rise-fall time.

Offset auditory brainstem response (ABR) traditionally has been thought to be an artifactual response elicited by stimulus acoustic ringing. Additionally, offset ABR's sensitivity to stimulus rise-fall time has been associated with concurrent changes in acoustic ringing. The present study tested the validity of offset ABR by recording the response in 40 young, normal-hearing adults using tone burst stimuli with varying degrees of acoustic ringing and various rise-fall times. Stimuli were computer-generated 10-ms tone bursts of 500 and 2000 Hz. In Experiment 1, offset ABR was recorded using stimuli with no acoustic ringing, normal ringing, and excessive ringing. Rise-fall time was held constant at 0.5 ms. In Experiment 2, rise-fall time was manipulated in a stimulus with no ringing. In Experiment 3, only rise time was manipulated in a no-ringing stimulus, while fall time was held constant at 0.5 ms. Reliable offset ABRs were recorded for all degrees of acoustic ringing, including the "no-ringing' condition. Offset ABR was sensitive to rise and fall times, and was elicited best with a 500-Hz stimulus. The results indicate that offset ABR is a real response and not an artifact produced by acoustic ringing.

Acoustic Stimulation↗

PubMed1997

Auditory development in complex tasks of comodulation masking release.

Experiments on listeners aged 5 years to adult were conducted to investigate the development of comodulation masking release (CMR) under conditions where auditory grouping could be affected either by the coherence of modulation pattern among noise bonds, or the temporal asynchrony among bands. The conditions examining CMR when two modulation patterns were present (each carried by a different set of noise bands) indicated a similar effect across all age groups. Here, CMR was substantial when the on-signal band (OSB) and six comodulated flanking bands (FBs) were presented, decreased when two bands having a second pattern of modulation were added, and then recovered partially when a further six bands that had the second modulation pattern were added. In conditions where there was a temporal asynchrony between the OSB and the FBs, the children typically showed smaller CMRs than the adults. In the case where the OSB preceded the FBs, adults typically showed CMR near zero when the temporal fringe was 50 ms or more. Children usually showed negative CMRs for such conditions. In the case where the FBs preceded the OSB, all age groups showed substantial CMRs, but the CMRs of adults were significantly larger than those of the children. The present results indicate that the effect of a second, independent modulation pattern on CMR is similar in children and adult listeners, but that CMR appears to be detrimentally affected more in children than in adults when there is a temporal asynchrony between the on-signal and flanking bands.

Adult↗

PubMed1997

MLD in children: effects of signal and masker bandwidths.

The first aim of this study was to obtain a more detailed picture of the effect of masker bandwidth (20 Hz to 1000 Hz bandwidth) on the masking level difference (MLD) for a 500-Hz signal as a function of listener age. The results of the pure-tone signal experiment showed that the MLDs of older children differed from adults only for the narrowest masker bandwidth. In contrast, children younger than about 7 years of age tended to have smaller MLDs than adults at all but the widest masker bandwidth must be for MLDs of adult magnitude to be observed. One interpretation of this effect is that younger listeners require relatively great spectral dissimilarity (and, therefore perceptual dissimilarity) between the signal and masker in order to obtain MLDs of adult magnitude. The second aim of this study was to test this possibility by determining the MLD for noise signals in cases where the signal and masker bandwidths were the same. The results of this experiment showed that the MLDs of children were as large as those of adults when the signal/masker bandwidth was 320 Hz, but were smaller than those of adults when the signal/masker bandwidth was 20 Hz. This indicates that the factor limiting the MLD for narrowband noise in children is related more to the masker bandwidth than to the perceptual similarity between the signal and the masker.

Adult↗

PubMed1997

The relation between gap detection, loudness, and loudness growth in noise-masked normal-hearing listeners.

Gap detection was measured for 50 and 1000-Hz-wide noise markers arithmetically centered on 1000 Hz. The markers were presented in a lowpass background noise having a high-frequency cutoff of 2000 Hz. The pressure spectrum level of the background noise was either 0 or 40 dB/Hz. Gap detection was determined at sensation levels (SLs) of 10, 15, 20, and 30 dB in the 0-dB/Hz background, and at SLs of 10, 15, and 20 dB in the 40-dB/Hz background. Because loudness increased more steeply in the higher level noise background, the markers in the 40-dB/Hz background were at higher loudness (and at a steeper portion of the loudness growth function) than markers in the 0-dB/Hz background, for markers matched in terms of SL. The main goal of the experiment was to determine whether gap detection would be relatively poor at steep portions of the loudness growth function due to the gap being confused with ongoing random dips. Such confusion might be particularly great when the noise bandwidth was narrow (and therefore characterized by prominent fluctuation) and the growth of loudness was steep. Gap detection was poorer for the 50-Hz-wide marker than for the 1000-Hz-wide marker. For a given marker bandwidth at a given SL, gap detection was similar whether the marker was presented in the 0-dB/Hz noise or the 40-dB/Hz noise. Supplementary conditions indicated that (1) gap detection results for 50-Hz-wide markers presented at equal SL's were also similar between a 0-dB/Hz noise background and a 55-dB/Hz noise background, and that (2) gap detection for 50- and 1000-Hz-wide markers was poorer in a 40-dB/Hz background than in a 0-dB/Hz background when markers were matched for loudness. The results generally indicated similar gap detection thresholds for markers presented at similar SLs across a relatively wide range of background noise levels. Gap detection was related more closely to the marker-to-noise ratio than to the loudness relation between markers or the steepness of loudness growth.

Auditory Threshold↗

PubMed1997

Multiband detection of energy fluctuations.

this study sought to characterize the integration of synchronous energy fluctuations across relatively independent spectral regions. The detection of four classes of signal was examined where each class of signal was associated with a change in energy over time. The four signal types were: (1) multicomponent tonal complexes, with each component centered in a narrow band of noise; (2) intensity increments in multiple narrow bands of noise; (3) intensity decrements in multiple narrow bands of noise; and (4) temporal gaps in multiple narrow bands of noise. Each signal type was examined in a separate experiment, although stimulus characteristics such as presentation level and frequency location were held constant. Experiment 1 confirmed that the detection of multitonal complexes masked by narrow bands of noise is linearly related to the square root of N, where N is the number of signal components. Experiment 2 extended this to show that, when the signal was an increment in the level of a noise band carrier, threshold continued to be a linear function of the square root of N, although threshold was about 2 dB higher than for a comparable tonal signal. Experiment 3 indicated that the detection of a decrement in energy in one or more noise bands was relatively poorer in terms of absolute level changes than was the detection of an energy increment in the same stimulus. Examination of psychometric functions for decrement detection suggested that performance improved by less than the square root of N. Experiment 4 found that gap detection improved with increasing N but by a factor greater than the square root of N expected on statistical grounds. Examination of the underlying psychometric functions confirmed this effect. The results of these experiments suggest that, for energy increments, the auditory system integrates information from across the spectrum in a statistically independent manner, at least over the frequency range examined here. This does not appear to be the case for the detection of energy gaps or decrements.

Adult↗

PubMed1997

Signal detection and pitch ranking in conditions of masking release.

Masked threshold levels for signal detection or pitch ranking (low, middle, or high) were determined in conditions where one of three possible signal frequencies could be presented on a given trial of a three-interval forced-choice task. Thresholds were determined under conditions investigating binaural masking release (the masking-level difference, or MLD) and monaural masking release in modulated noise. It was assumed that part of the masking release in modulated noise was due to a within-channel analysis of information in the masker dips, and that part of the masking release was due to across-frequency analysis of temporal envelope information (comodulation masking release, or CMR). In the MLD experiment, the masker was a low-pass noise with a frequency cutoff of 1000 Hz. In the modulated-noise experiment, a broadband noise was square-wave amplitude modulated at a rate of 25 Hz and then digitally low-passed filtered at 1000 Hz. The results indicated that when the frequency separation between frequency components was relatively wide, masking release for pitch ranking was similar to that for signal detection. However, as the frequency separation between components narrowed, masking release for pitch ranking decreased. The results are consistent with an interpretation that information regarding signal frequency is relatively coarse under the conditions of masking release examined here.

Adult↗

PubMed1997

Auditory brainstem response: recent developments in recording and analysis.

During the past 25 years since the 'discovery' of the ABR, clinicians world-wide have exploited the clinical utility of this evoked response with many different populations. The 1970s and 1980s saw the development of ABR protocols for increasing the reliability and validity of the response in various clinical situations. Now, in the last decade of the century, advanced technology and the development of increasingly sophisticated software allows more flexibility in these measurements. Thus, ABR testing continues to evolve at a rapid pace. The main focus for ABR in the 1990s has been on developing techniques to improve the quality of the response, decrease the time in which it takes to record the response, and minimize human error through objective response analysis. Some of the major recent developments were reviewed in this chapter. The intent of this review is to provide the researcher and the clinician with an understanding of the underlying principles of the techniques which will be, and are already, available to them on their ABR equipment. Many of these techniques are promising for use with newborns, children, and difficult-to-test populations where time is a limiting factor in the amount of information that can be obtained. We encourage any and all clinicians to experiment with these techniques to determine how each technique might contribute to their particular clinic protocols. As with any new technique, there will be a learning curve associated with understanding the underlying principles, mastering the technical requirements, and realizing the most valuable clinical applications of these methods. Once the procedures become familiar to clinicians and applied in varied clinical settings, it is likely that the neurodiagnostic and audiologic value of ABR will be profoundly enhanced.

Auditory Threshold↗

PubMed1997

Factors affecting the recordability of auditory evoked response component Pb (P1).

The auditory middle latency response (AMLR) is characterized by two positive peaks (Pa, Pb) and two negative peaks (Na, Nb). The unpredictable nature of the second positive peak, Pb or P1, has made its diagnostic use problematic. Our purpose was to determine an appropriate combination of stimulating and recording variables that evoked a repeatable Pb in adults and children. Three experiments were designed to evaluate systematically the amplitude and latency of the Pb as a function of duration, stimulus type (500- and 4000-Hz tone bursts and clicks), repetition rate (0.5, 0.7, 1.1, 2.1, and 5.1/sec), and electrode array. Results showed that a longer duration (60 msec), low-frequency (500-Hz) tone burst consistently evoked the Pb in all subjects. Results also showed that a longer interstimulus interval (1.1/sec) is more likely to evoke the Pb component. Additionally, results showed that Pb is generally largest when recorded from a noninverting electrode at Fz with a noncephalic reference. Finally, results showed that Pb latency is significantly longer and amplitude larger in children than in adults.

Adolescent↗

PubMed1996

Chick cartilage fibronectin differs in structure from the fibronectin in limb mesenchyme.

Fibronectin, present in the extracellular matrix of several tissues, is heterogeneous in structure. This heterogeneity is largely due to the alternative splicing of three exons (IIIB, IIIA, and V) during processing of the fibronectin primary transcript. Previously, we determined that the splicing patterns of fibronectin mRNAs change from B+A+ to B+A- during the differentiation of mesenchyme into cartilage (V. D. Bennett, K. M. Pallante, and S. L. Adams, J. Biol. Chem. 266, 5918-5924, 1991). Therefore, the structure of fibronectin at the protein level most likely changes during chondrogenesis as well. In order to characterize the fibronectin protein in chick limb prechondrogenic mesenchyme and cartilage, we generated a polyclonal antibody specific for the region encoded by exon IIIB in the chick fibronectin gene. Immunoblot and immunohistochemistry analyses with this antibody and an antibody specific for the region encoded by exon IIIA indicate that both antibodies react with the fibronectin present in prechondrogenic mesenchyme. In contrast, only the exon IIIB antibody reacts with the fibronectin present in chick cartilage. Quantitative ELISA assays with these antibodies indicate that approximately 96% of the fibronectin in chick embryonic cartilage contains exon IIIB while less than 3% of the fibronectin contains exon IIIA. These results corroborate the structures of the fibronectin isoforms present in prechondrogenic mesenchyme and cartilage that were predicted from our previous characterization of the fibronectin mRNAs in these tissues and indicate that essentially all of the fibronectin in cartilage is synthesized and secreted by cartilage chondrocytes.

Alternative Splicing↗