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Biomedical subjects

J H Grose

Publications and source records attributed to J H Grose.

At least 19 recordsLinked to original sources
PubMed1998

Chronic conductive hearing loss in adults: effects on the auditory brainstem response and masking-level difference.

OBJECTIVE: To determine whether chronic conductive hearing loss in adults results in changes in the auditory brainstem response (ABR) similar to those observed in children with histories of otitis media with effusion. DESIGN: Test of effect of unilateral conductive hearing loss on adult ABR using age-matched control group and subjects as their own controls. SUBJECTS: Twelve adults with a history of unilateral conductive ear disease. An age-matched control group of 21 adults was also tested. METHODS: The ABR, an electrophysiologic test of auditory brainstem functioning, was used to evaluate possible brainstem abnormalities in the impaired listeners. In addition, the masking-level difference, a behavioral test of binaural auditory processing in the brainstem, was used. RESULTS: When comparing the patients' diseased ears with their healthy ears, significant delays were seen for wave V as well as for the I-V and III-V interwave intervals. For comparison with the control population, significant prolongations were again seen for wave V and for the III-V interwave intervals. In addition, reduced masking-level differences and significant correlations between the masking-level differences and the ABRs, independent of hearing threshold, were noted. CONCLUSIONS: The results suggest that chronic conductive impairment in adults leads to changes in the ABR similar to those observed in children with histories of otitis media with effusion. As such, these changes do not appear to be related to a critical period of development.

Adult↗
PubMed1998

The effect of otitis media with effusion on complex masking tasks in children.

OBJECTIVE: To determine whether there is a relationship between the presumed complexity of auditory processing and the time course of recovery of auditory function in children with a history of otitis media with effusion (OME). DESIGN: Longitudinal testing over a 1-year period following insertion of tympanostomy tubes in clinical and control groups. SUBJECTS: A total of 34 children with a history of OME were tested. Twenty-five were tested both just before the placement of tympanostomy tubes and on up to 3 separate occasions (1 month, 6 months, and 1 year) after the placement of the tubes. With subject attrition, there were 27, 16, and 10 listeners at the 1-month, 6-month, and 1-year tests, respectively. An age-matched control group of 29 children was tested. METHODS: The comodulation masking release (CMR) paradigm was used to measure the ability of the listener to detect a signal in a noise background composed of a simple (1 amplitude modulation pattern) or more complex (2 amplitude modulation patterns) masking background. RESULTS: Children with a history of OME had reduced masking release before and 1 month after insertion of tympanostomy tubes for both the simple and complex CMR tasks. After surgery, the CMR results for simple task was not significantly different from that in controls by 6 months, but CMR for the complex task remained significantly reduced even 1 year after surgery. CONCLUSION: Our results suggest a slower recovery of auditory function for more complex auditory tasks in children with a history of OME.

Auditory Perception↗
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

Effects of losartan and captopril on endothelin-1 production in blood vessels and glomeruli of rats with reduced renal mass.

Recently, we have reported that endothelin-1 (ET-1) production is increased in blood vessels and glomeruli of rats with chronic renal failure. This study was design to investigate the role of angiotensin II (Ang II) in endogenous ET-1 production in rats with reduced renal mass. One week after subtotal (5/6) nephrectomy, uremic rats were divided into three groups, and received either no treatment, the Ang II subtype 1 receptor (AT1) antagonist losartan (10 mg/kg/day), or the angiotensin-converting enzyme inhibitor (ACE-I) captopril (30 mg/kg/day) for 6 weeks. Sham-operated rats were used as controls and received no treatment. The levels of immunoreactive ET-1 (ir-ET-1) in plasma and urine, as well as in vascular and renal tissues, were determined by radioimmunoassay (RIA) after extraction. In uremic rats, losartan and captopril completely prevented the increase in systolic blood pressure. At week 6, plasma ir-ET-1 was similar in the different groups of uremic rats and in the controls. However, ir-ET-1 concentration in the mesenteric arterial bed, the thoracic aorta, preglomerular arteries, and glomeruli, as well as urinary ir-ET-1 excretion were significantly greater in uremic-untreated rats compared to controls (P < .01). Treatment of uremic rats with losartan or captopril reduced irET-1 concentration in the thoracic aorta and preglomerular arteries (P < .05), but ir-ET-1 concentration in the mesenteric arterial bed was unchanged. Although both drugs completely prevented the increase in proteinuria, losartan but not captopril significantly reduced ir-ET-1 concentration in glomeruli (P < .05) and normalized urinary ir-ET-1 excretion. This indicates that increased ET-1 production in blood vessels and glomeruli of uremic rats is modulated, at least in part, by Ang II through the AT1 receptor. The beneficial effects of the AT1 antagonist losartan could be attributable to the attenuation of Ang II-induced ET-1 production in this rat remnant kidney model of chronic renal failure, whereas those of the ACE-I captopril are not related to changes in ET-1 production in glomeruli.

Angiotensin II↗
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

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

Hemodynamic and hormonal changes during erythropoietin therapy in hemodialysis patients.

To better understand the mechanism of recombinant human erythropoietin (rhEPO)-induced increase in BP, hemodynamic parameters, body fluid volumes, and the hormones implicated in BP regulation were studied in 32 anemic hemodialysis patients before and after 3 to 4 mo of rhEPO therapy. Hemoglobin levels increased from 83 +/- 1.5 to 119 +/- 2.3 g/L (P < 0.01) after rhEPO therapy (25 to 43 U/kg) administered subcutaneously three times weekly. Mean 24-h systolic and diastolic ambulatory BP were significantly increased by 14 +/- 3 and 10 +/- 2 mmHg, respectively (P < 0.01 for both groups). Systemic vascular resistance consistently increased by 28 +/- 5% (P < 0.01), whereas cardiac output was decreased by 6 +/- 3% (P < 0.05). Red blood cell mass increased by 510 +/- 35 ml (P < 0.01), whereas plasma volume decreased by 420 +/- 66 ml (P < 0.01), which resulted in a nonsignificant increase in total blood volume. Extracellular fluid volume and exchangeable sodium were decreased by 873 +/- 255 ml (P < 0.01) and 125 mmol (P < 0.01), respectively. There was a positive correlation between the changes in exchangeable sodium and in systolic BP (r = 0.41, P < 0.05). Furthermore, a greater increase in 24-h systolic BP was observed in patients in whom exchangeable sodium increased or remained unchanged (n = 10) compared with patients (n = 22) with decreased exchangeable sodium (20 +/- 4 mmHg versus 8 +/- 2 mmHg, respectively, P < 0.01). Plasma catecholamines, plasma renin concentration, plasma atrial natriuretic peptide, and plasma endothelin-1 did not significantly change with rhEPO treatment, whereas plasma aldosterone increased significantly (P < 0.01). Although volume-independent mechanisms may contribute to rhEPO-induced BP increase, the results presented here suggest the importance of optimally reducing extracellular fluid volume to prevent, at least in part, the development of hypertension often observed with improved uremic anemia in these patients.

Adolescent↗
PubMed1998

Plasma and blood vessel endothelin-1 concentrations in hypertensive uremic rats treated with erythropoietin.

The present study was designed to evaluate whether changes in plasma and blood vessel endothelin-1 (ET-1) concentrations may play a role in the enhanced blood pressure response to recombinant human erythropoietin (r-HuEPO) replacement therapy in uremia. Renal failure was induced by 5/6 nephrectomy (Nx). Uremic rats received either r-HuEPO (100 u s.c. three times a week) or the vehicle for 5 weeks. They were compared to control rats receiving the vehicle. Systolic blood pressure (tail cuff method), hematocrit, serum creatinine, plasma and tissue ET-1 were measured at the end of the protocol. Immunoreactive ET-1 (ir-ET-1) was determined by radioimmunoassay of acid-extracts from the plasma, thoracic aorta and mesenteric arterial bed. Creatinine increased about three fold in Nx animals. Blood pressure in control rats was 120+/-3 mmHg compared to 161 +/-6 mmHg in the Nx + vehicle group (p <0.01) and 199+/-9 mmHg in the Nx + r-HuEPO group (p <0.01 vs Nx + vehicle). Hematocrit in control rats was 41.3+/-0.4% vs 32.6+/-1.8% in the Nx + vehicle group (p <0.01) and 47.6+/-1.5% in the Nx + r-HuEPO group (p <0.01). Plasma ir-ET-1 levels were similar in the Nx + vehicle and Nx + r-HuEPO groups (7.9+/-1.0 and 7.8+/-0.8 pg/ml). In contrast, thoracic aorta ir-ET-1 content was significantly higher in the Nx + r-HuEPO group than in the Nx + vehicle group (20.3+/-2.9 vs 13.4+/-1.9 pg, p <0.05). Similar results were obtained in the mesenteric arterial bed. There were significant correlations between blood pressure and ir-ET-1 content in the thoracic aorta (r= 0.45, p<0.05) and in the mesenteric arterial bed (r= 0.41, p<0.05). Vascular ET-1 content but not plasma levels are increased in uremic rats treated with r-HuEPO suggesting an increase in blood vessel ET-1 production which may play a role in the pathogenesis of r-HuEPO-induced hypertension.

Animals↗
PubMed1998

Plasma and peritoneal endothelin levels and blood pressure in CAPD patients with or without erythropoietin replacement therapy.

The aim of the study was to determine the ET-1 concentration in peritoneal dialysate fluid and to investigate the relationship between peritoneal and plasma ET-1 levels and blood pressure in stable continuous ambulatory peritoneal dialysis (CAPD) patients with and without human recombinant erythropoietin (r-HuEPO) replacement therapy. Twenty-seven stable CAPD patients were investigated. They completed their overnight exchange at the Dialysis Centre. Blood pressure was recorded and a blood sample was drawn. Biochemical parameters and ET-1 were measured in plasma and peritoneal dialysate fluid. Mean plasma ET-1 levels were increased by about four-fold in CAPD patients. ET-1 was detectable in peritoneal dialysate fluid and a significant correlation was observed between plasma and peritoneal ET-1 concentrations (r = 0.65, p < 0.01). The peritoneal clearance of ET-1 was lower than the creatinine clearance (1.69 +/- 0.08 ml/min vs. 3.96 +/- 0.15 ml/min, p < 0.01). There was also a significant correlation between the time (months) on dialysis and plasma (r = 0.68, p < 0.01) or peritoneal dialysate ET-1 levels (r = 0.46, p < 0.05). Mean blood pressure was higher in patients treated with r-HuEPO than in untreated patients (97 +/- 4 mmHg vs. 81 +/- 4 mmHg, p < 0.01). Plasma and peritoneal dialysate ET-1 concentrations were comparable in the two groups with or without r-HuEPO replacement therapy and plasma ET-1 values correlated significantly with mean blood pressure only in r-HuEPO-treated patients (r = 0.63, p < 0.05 vs. r = 0.10, N.S. in untreated patients). In conclusion, plasma ET-1 concentrations are elevated in CAPD patients and the levels appear to increase with time on dialysis. ET-1 is cleared by the peritoneal membrane but at a much lower rate than creatinine. Blood pressure is higher in CAPD patients or r-HuEPO replacement therapy and blood pressure correlates with plasma ET-1 levels in these patients.

Ascitic Fluid↗
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↗