Biomedical subjects

J R Dubno

Publications and source records attributed to J R Dubno.

At least 19 recordsLinked to original sources

PubMed2001

The amplitude-modulation following response in young and aged human subjects.

The amplitude-modulation following response (AMFR) is a steady-state auditory response which may be an objective measure of intensity discrimination. Aged subjects with normal hearing have poorer intensity discrimination for low-frequency tones measured behaviorally, which would predict poorer AMFRs for low-frequency carriers. Experiment 1 was designed to assess age-related differences in AMFR characteristics. Response amplitudes were not significantly different among the young and aged groups for either carrier frequency (520 or 4000 Hz) or modulation depth (0--100%). Response phase did not vary systematically among groups. These results suggest that the AMFR may not be directly comparable to behavioral measures of intensity discrimination in aged subjects with normal hearing. To assess the contribution of high-frequency hearing loss on the AMFR in aged subjects, Experiment 2 compared AMFR amplitudes in aged subjects and in young subjects under the condition of high-pass masking. The amplitude of the AMFR was reduced at 520 Hz for both aged subjects and masked young subjects compared to unmasked young subjects, suggesting that reduced amplitudes in aged subjects with high-frequency hearing loss were associated with threshold elevations. Furthermore, the results suggest that the base of the cochlea contributes to the AMFR for low carrier frequencies.

Acoustic Stimulation↗

PubMed2001

Auditory brainstem responses in younger and older adults for broadband noises separated by a silent gap.

Wave V of the auditory brainstem response was measured to two 50-ms broadband noise bursts separated by silent gaps of varied duration (4, 8, 32, or 64 ms) for younger and older adults with normal hearing. All subjects had measurable wave V responses to the first noise burst. However, for the second noise burst, three of eight older adults did not have responses with gap durations of 4 and 8 ms, and one of eight younger adults did not have a measurable response with a gap duration of 4 ms. When responses were present for older adults, latencies were similar to those of younger subjects but amplitudes were smaller. These results suggest age-related deficits in gap detection at the level of the brainstem in a group of aged subjects with no threshold elevation. Results are similar to those of Boettcher et al. (1996) using an identical paradigm in young and aged Mongolian gerbils.

Acoustic Stimulation↗

PubMed2001

Forward- and simultaneous-masked thresholds in bandlimited maskers in subjects with normal hearing and cochlear hearing loss.

Forward- and simultaneous-masked thresholds were measured at 0.5 and 2.0 kHz in bandpass maskers as a function of masker bandwidth and in a broadband masker with the goal of estimating psychophysical suppression. Suppression was operationally defined in two ways: (1) as a change in forward-masked threshold as a function of masker bandwidth, and (2) as a change in effective masker level with increased masker bandwidth, taking into account the nonlinear growth of forward masking. Subjects were younger adults with normal hearing and older adults with cochlear hearing loss. Thresholds decreased as a function of masker bandwidth in forward masking, which was attributed to effects of suppression; thresholds remained constant or increased slightly with increasing masker bandwidth in simultaneous masking. For subjects with normal hearing, slightly larger estimates of suppression were obtained at 2.0 kHz rather than at 0.5 kHz. For hearing-impaired subjects, suppression was reduced in regions of hearing loss. The magnitude of suppression was strongly correlated with the absolute threshold at the signal frequency, but did not vary with thresholds at frequencies remote from the signal. The results suggest that measuring forward-masked thresholds in bandlimited and broadband maskers may be an efficient psychophysical method for estimating suppression.

Adult↗

PubMed2001

Psychophysical suppression measured with bandlimited noise extended below and/or above the signal: effects of age and hearing loss.

The objectives of this study were to measure suppression with bandlimited noise extended below and above the signal, at lower and higher signal frequencies, between younger and older subjects, and between subjects with normal hearing and cochlear hearing loss. Psychophysical suppression was assessed by measuring forward-masked thresholds at 0.8 and 2.0 kHz in bandlimited maskers as a function of masker bandwidth. Bandpass-masker bandwidth was increased by introducing noise components below and above the signal frequency while keeping the noise centered on the signal frequency, and also by adding noise below the signal only, and above the signal only. Subjects were younger and older adults with normal hearing and older adults with cochlear hearing loss. For all subjects, suppression was larger when noise was added below the signal than when noise was added above the signal, consistent with some physiological evidence of stronger suppression below a fiber's characteristic frequency than above. For subjects with normal hearing, suppression was greater at higher than at lower frequencies. For older subjects with hearing loss, suppression was reduced to a greater extent above the signal than below and where thresholds were elevated. Suppression for older subjects with normal hearing was poorer than would be predicted from their absolute thresholds, suggesting that age may have contributed to reduced suppression or that suppression was sensitive to changes in cochlear function that did not result in significant threshold elevation.

Adult↗

PubMed2001

Psychophysical suppression effects for tonal and speech signals.

This experiment assessed the benefits of suppression and the impact of reduced or absent suppression on speech recognition in noise. Psychophysical suppression was measured in forward masking using tonal maskers and suppressors and band limited noise maskers and suppressors. Subjects were 10 younger and 10 older adults with normal hearing, and 10 older adults with cochlear hearing loss. For younger subjects with normal hearing, suppression measured with noise maskers increased with masker level and was larger at 2.0 kHz than at 0.8 kHz. Less suppression was observed for older than younger subjects with normal hearing. There was little evidence of suppression for older subjects with cochlear hearing loss. Suppression measured with noise maskers and suppressors was larger in magnitude and more prevalent than suppression measured with tonal maskers and suppressors. The benefit of suppression to speech recognition in noise was assessed by obtaining scores for filtered consonant-vowel syllables as a function of the bandwidth of a forward masker. Speech-recognition scores in forward maskers should be higher than those in simultaneous maskers given that forward maskers are less effective than simultaneous maskers. If suppression also mitigated the effects of the forward masker and resulted in an improved signal-to-noise ratio, scores should decrease less in forward masking as forward-masker bandwidth increased, and differences between scores in forward and simultaneous maskers should increase, as was observed for younger subjects with normal hearing. Less or no benefit of suppression to speech recognition in noise was observed for older subjects with normal hearing or hearing loss. In general, as suppression measured with tonal signals increased, the combined benefit of forward masking and suppression to speech recognition in noise also increased.

Adult↗

PubMed2000

Use of context by young and aged adults with normal hearing.

Word recognition in sentences with and without context was measured in young and aged subjects with normal but not identical audiograms. Benefit derived from context by older adults has been obscured, in part, by the confounding effect of even mildly elevated thresholds, especially as listening conditions vary in difficulty. This problem was addressed here by precisely controlling signal-to-noise ratio across conditions and by accounting for individual differences in signal-to-noise ratio. Pure-tone thresholds and word recognition were measured in quiet and threshold-shaped maskers that shifted quiet thresholds by 20 and 40 dB. Word recognition was measured at several speech levels in each condition. Threshold was defined as the speech level (or signal-to-noise ratio) corresponding to the 50 rau point on the psychometric function. As expected, thresholds and slopes of psychometric functions were different for sentences with context compared to those for sentences without context. These differences were equivalent for young and aged subjects. Individual differences in word recognition among all subjects, young and aged, were accounted for by individual differences in signal-to-noise ratio. With signal-to-noise ratio held constant, word recognition for all subjects remained constant or decreased only slightly as speech and noise levels increased. These results suggest that, given equivalent speech audibility, older and younger listeners derive equivalent benefit from context.

Adult↗

PubMed2000

Experience with a yes-no single-interval maximum-likelihood procedure.

The report in 1993 by Green [J. Acoust. Soc. Am. 93, 2096-2105 (1993)] describing the application of a new psychophysical method requiring few trials and little time to measure auditory thresholds has generated considerable interest among experimentalists. The procedure uses a single-interval stimulus presentation, requests a yes-no decision by subjects, and implements a maximum-likelihood calculation to determine the next trial stimulus level within an adaptive track, as well as the final threshold estimate. Data are presented here describing separate experiences with this procedure in two laboratories in both detection and discrimination tasks. Issues addressed include comparisons with more traditional psychophysical methods, variability in threshold estimates, experimental time required, and possible minor modifications to improve the basic procedure. Results using this procedure are comparable in terms of variability of estimates to those emerging from more lengthy procedures. However, because it may be difficult for some listeners to maintain a consistent criterion and because attentional lapses may be costly, experimenters must be willing to monitor performance closely and repeat some tracks in cases where excessively high variability is noted. Further, this procedure may not be suitable for tasks for which the form of the psychometric function is not well-established. Modifications allowing a variable slope parameter in the maximum-likelihood evaluations of psychometric functions may be of benefit.

Attention↗

PubMed1999

Gender-specific effects of drugs on hearing levels of older persons.

As part of a study of human presbyacusis, a questionnaire on medicinal drug usage was given to 357 subjects (184 females, 173 males). Previous results from 211 subjects showed gender effects, that is, for males, none of the drugs had any measurable effects on hearing, whereas women taking calcium channel blockers (CCBs) had hearing levels 12 dB better than women not taking them; women taking beta adrenergic medication had hearing levels 20 dB poorer, and women taking antihistamine/cold preparations had hearing levels 9 dB poorer. Results from the original 211 subjects were confirmed when the sample size was increased from 211 to 357 subjects only for the beta adrenergic medications. Results for antihistamine/cold preparation medications showed small effects only for female subjects. Data from 13 additional female subjects who used CCBs showed hearing levels 10-14 dB poorer than predicted from the original data. Male data were consistent in both samples. The inconsistency for females could reflect sampling error. A more likely possibility is that since the original 10 subjects using CCBs had a mean age of 72 yr and the second sample of 13 had a mean age of 79.5 yr, poorer hearing levels might be anticipated because of the difference in chronological age and possibly duration of drug usage.

Adrenergic beta-Agonists↗

PubMed1999

Feasibility of using fMRI to study mothers responding to infant cries.

While parenting is a universal human behavior, its neuroanatomic basis is currently unknown. Animal data suggest that the cingulate may play an important function in mammalian parenting behavior. For example, in rodents cingulate lesions impair maternal behavior. Here, in an attempt to understand the brain basis of human maternal behavior, we had mothers listen to recorded infant cries and white noise control sounds while they underwent functional MRI (fMRI) of the brain. We hypothesized that mothers would show significantly greater cingulate activity during the cries compared to the control sounds. Of 7 subjects scanned, 4 had fMRI data suitable for analysis. When fMRI data were averaged for these 4 subjects, the anterior cingulate and right medial prefrontal cortex were the only brain regions showing statistically increased activity with the cries compared to white noise control sounds (cluster analysis with one-tailed z-map threshold of P < 0.001 and spatial extent threshold of P < 0.05). These results demonstrate the feasibility of using fMRI to study brain activity in mothers listening to infant cries and that the anterior cingulate may be involved in mothers listening to crying babies. We are currently replicating this study in a larger group of mothers. Future work in this area may help (1) unravel the functional neuroanatomy of the parent-infant bond and (2) examine whether markers of this bond, such as maternal brain response to infant crying, can predict maternal style (i.e., child neglect), offspring temperament, or offspring depression or anxiety.

Adult↗

PubMed1999

Psychometric functions for gap detection in noise measured from young and aged subjects.

Psychometric functions for gap detection of temporal gaps in wideband noise were measured in a "yes/no" paradigm from normal-hearing young and aged subjects with closely matched audiograms. The effects of noise-burst duration, gap location, and uncertainty of gap location were tested. A typical psychometric function obtained in this study featured a steep slope, which was independent of most experimental conditions as well as age. However, gap thresholds were generally improved with increasing duration of the noise burst for both young and aged subjects. Gap location and uncertainty had no significant effects on the thresholds for the young subjects. For the aged subjects, whenever the gap was sufficiently away from the onset or offset of the noise burst, detectability was robust despite uncertainty about the gap location. Significant differences between young and aged subjects could be observed only when the gap was very close to the signal onset and offset.

Adult↗

PubMed1999

Determination of optimal data placement for psychometric function estimation: a computer simulation.

Psychometric functions are used to relate the responses of a subject to physical stimuli in a variety of psychophysical tasks. However, it is time consuming to obtain data to determine a psychometric function if many stimulus levels and many trials are required. A computer simulation was conducted to determine the minimum number of data points needed for such a determination. The computer simulation also determined the optimal placements of the stimuli and the number of trials per datum point for psychometric function determinations. Results indicate that a 2-point sampling method with 30-50 trials per point at optimal locations can produce a psychometric function with accurate spread and threshold estimates in a yes-no paradigm. However, the 4-point sampling method yields statistically smaller variances of the estimates. For the 2-alternative forced-choice paradigm, at least 120 trials per point are needed for the 2-point sampling method's estimated parameters to differ from the known parameter values by less than 5%. The simulation results suggest that 3-alternative or 4-alternative forced-choice is preferable to 2-alternative. Furthermore, when a criterion-free paradigm is not required, the yes-no paradigm is a better procedure than m-alternative forced-choice for obtaining the corresponding psychometric function because of smaller standard deviation of the estimates and smaller number of trials/point required.

Computer Simulation↗

PubMed1998

Gender-specific effects of medicinal drugs on hearing levels of older persons.

As part of a large-scale study of presbyacusis, responses to a medicinal drug questionnaire from 85 female and 126 male human subjects were analyzed. Medicinal drugs were divided into 35 categories based on their pharmacologic effects. Subjects' ages ranged from 60 to 82 years. At least 10% of subjects reported taking drugs in 14 of 35 categories. Results were significantly different between female and male subjects. In men, none of the 14 categories showed a statistically significant relation to the pure-tone average (PTA) of 500, 1000, 2000, and 4000 Hz. In women, 3 of the 14 categories showed a statistically significant relation to the PTA. First, the average PTA of female subjects taking beta-adrenergic medication was 20 dB higher (poorer) than those not taking beta-adrenergic medication. Second, women taking antihistamine/cold preparations had an average PTA 9 dB higher (poorer) than those not taking antihistamine/cold preparations. Third, the average PTA of women taking calcium-channel blockers (CCBs) was 12 dB lower (better) than those not taking CCBs. In men, however, these drugs produced effects on the PTA of less than 3 dB. Differences between women and men were not explainable by differences in age or hearing level.

Adrenergic beta-Agonists↗

PubMed1998

Analysis of blood chemistry and hearing levels in a sample of older persons.

OBJECTIVE: As part of an ongoing study of presbyacusis, the relationship between blood chemistry levels and hearing levels was investigated. Previous reports often used small sets of blood chemistry measures, and results were inconclusive. This experiment examined hearing levels and 27 measures of blood chemistry using various univariate and multivariate statistical procedures. DESIGN: Blood from 89 female and 128 male human subjects was collected. Subjects' ages ranged from 60 to 82 yr, and hearing levels ranged from normal to moderate/severe. Subjects with a history of middle ear disease were excluded. Electrolyte panel (Na, K, Cl, CO2, Ca, urea nitrogen, glucose, creatinine, and Mg), hematology panel (WBC, RBC, Hgb, hematocrit, platelet, etc.), serum lipids (total cholesterol, low-density lipoprotein [LDL], and high-density lipoprotein [HDL]), immunoglobulins (IgG, IgA, IgM, and IgE), and thyroxine were analyzed using univariate and multivariate statistical procedures. RESULTS: Blood chemistry levels of most subjects were within normal ranges as defined by our laboratory. Correlation between blood chemistry measures and pure-tone averages (PTAs) ranged from minimal to low. Results of factor analysis, discriminant analysis, and canonical analysis showed that combining blood chemistry measures from the same panel still could not predict PTA effectively. One exception to this was a gender-specific effect of cholesterol. Hearing levels of women with high LDL/HDL ratios were 5 dB better than those of women with low LDL/HDL ratios. The comparable difference in men was only 1 dB. CONCLUSION: Results suggest that blood chemistry measures that are primarily within the normal range have very little value in predicting pure-tone thresholds in older subjects.

Age Factors↗

PubMed1998

Frequency and intensity discrimination measured in a maximum-likelihood procedure from young and aged normal-hearing subjects.

A maximum-likelihood method was applied in measurements of frequency and intensity discrimination for aged and young normal-hearing subjects with closely matched audiograms. This method was preferred over other psychophysical procedures because it is efficient and controls experimental variance, features that are highly desirable for testing aged subjects. In order to implement the method, psychometric functions for each task were also measured from young subjects using a constant-stimuli procedure. For the young subjects, the differential thresholds obtained from these two procedures were generally comparable. Further, both sets of data were consistent with previous literature, indicating that the maximum-likelihood method was successfully applied for frequency and intensity discrimination. A frequency-dependent difference between young and aged subjects in both frequency and intensity discrimination was observed. Even with closely matched audiograms, aged subjects demonstrated poorer discrimination abilities than young subjects. The age-related difference was always largest at 500 Hz and decreased as frequency increased.

Adolescent↗

PubMed1998

Interaction of noise-induced hearing loss and presbyacusis.

A medical-legal and scientific topic of longstanding interest is the interaction between presbyacusis and noise-induced permanent threshold shift (NIPTS). Current medical-legal practices as well as international standard, ISO 1999 International Organization for Standards: Acoustics: Determination of Occupational Noise Exposure and Estimation of Noise-Induced Hearing Impairment. ISO 1999. Geneva, International for Standards, 1990 assume that NIPTS and hearing loss caused by the aging process add in dB. Results of laboratory studies with animals are inconsistent in their support of the "additivity assumption". When intense, short-duration exposures are used, the predictions of the combined effects of noise and age are too large. The additivity model appears to be supported with long-duration exposures, but we question the accuracy of such predictions. The animal studies reviewed here suggest that the allocation of hearing loss in an older individual into a noise component and an aging component is much more complex than "additivity in dB".

Aged↗

PubMed1997

Extended high-frequency thresholds in older adults.

Most measures of auditory sensitivity at extended high frequencies (frequencies greater than 8 kHz) have been obtained from listeners with normal hearing less than 40 years of age. The purpose of this study was (a) to measure thresholds at frequencies above 8 kHz in older listeners who, as a group, have elevated thresholds at lower frequencies, and (b) to assess test-retest reliability, age and gender effects, and the influence of thresholds below 8 kHz. Extended high-frequency (EHF) thresholds were measured for 162 older listeners (60-79 years) using a commercially available high-frequency audiometer, with a frequency range of 8 to 18 kHz and an intensity range of 0 to 110 dB SPL. Thresholds were measured once at the beginning of a 1- to 2-hour test session and then remeasured at the end of the test session. EHF thresholds of older listeners with normal hearing at conventional audiometric frequencies were substantially higher than the thresholds reported for younger listeners, with normal hearing by Dreschler and van der Hulst (1987). EHF thresholds of older listeners with hearing loss at conventional audiometric frequencies were further elevated as compared to older listeners with normal hearing. Differences in EHF thresholds between females and males were either not present or were reduced when gender differences in conventional audiometric thresholds were taken into account. No significant differences were seen in thresholds at 8 kHz and higher between the 60- to 69-and 70- to 79-year-old age groups. Results also indicated that thresholds above 8 kHz can be measured in older listeners within a clinically acceptable +/- 10 dB test-retest range.

Age Factors↗

PubMed1997

Age-related and gender-related changes in monaural speech recognition.

Previous studies of older listeners suggest age-related declines in speech recognition. However, the interpretation of these results is not straightforward because auditory thresholds, which account for the largest proportion of the variance in speech-recognition scores, also vary considerably with age. Here, effects of age, gender, and auditory thresholds on several measures of speech recognition were assessed for a large sample of individuals enrolled in a longitudinal study of age-related hearing loss. Participants ranged in age from 55-84 years. They were evaluated with a battery of conventional audiometric measures and speech-recognition materials, including NU-6 monosyllabic words, Synthetic Sentence Identification sentences, and high-context and low-context sentences from the Speech Perception in Noise test. Two analyses were conducted to assure that changes in speech-recognition scores with age were examined independently of age-related changes in auditory thresholds. In the first analysis, no significant differences in speech recognition were observed for individuals in three age groups (55-64, 65-74, 75-84 years) who were selected so that average puretone thresholds for the groups were within 5 dB. In the second analysis, using partial correlations to adjust both score and age for their association with average thresholds, significant declines with age were observed for males in maximum word recognition, maximum synthetic sentence identification, and keyword recognition in high-context sentences. For females, no significant changes in speech recognition with age were observed for any test.

Age Factors↗

PubMed1997

Interaction of noise-induced permanent threshold shift and age-related threshold shift.

Current medical-legal practices as well as an international standard (ISO 1999) assume the permanent threshold shifts produced by exposure to noise add (in dB) to the threshold shifts caused by increased chronological age (presbyacusis). This assumption, known as the additivity rule, was tested in an animal model. Mongolian gerbils, born and raised in a quiet vivarium, were exposed at age 18 months to a 3.5-kHz pure tone for 1 h at 113 dB SPL. At 6-weeks post-exposure, permanent threshold shifts in the exposed ear were approximately 20 dB in the 4- to 8-kHz region. Thresholds in the nonexposed, control ear were unaffected by the exposure. Animals were then allowed to age in the quiet vivarium until age 36 months and then were retested. Thus in a given animal, aging-only effects were assessed in one ear (internal control) and noise-plus-aging effects were assessed in the other (test) ear. A second control was mean age-related threshold shift measured in 48 gerbils who were born and raised in the quiet vivarium. This group is referred to as a non-noise-exposed population (population control). Using the additivity rule, predictions with either the internal or population control significantly overestimated noise-plus-aging effects. Use of the ISO 1999 compression factor reduced the overestimations by 0-5 dB. The intensity rule produced the most accurate predictions. These results suggest that the interaction of noise-induced permanent threshold shift and age-related threshold shift is not straightforward and that current medical-legal methods using the additivity rule overestimate the contribution of "noise effects".

Age Factors↗