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Biomedical subjects

E Buss

Publications and source records attributed to E Buss.

At least 19 recordsLinked to original sources
PubMed2001

Gap duration discrimination in listeners with cochlear hearing loss: effects of gap and marker duration, frequency separation, and mode of presentation.

This study examined the effects of cochlear hearing loss on gap duration discrimination (GDD), with particular interest in whether cochlear hearing loss results in increased difficulty for across-channel temporal judgments. The hypothesis being tested was that listeners with cochlear loss would perform as well as normal-hearing listeners for all within-channel conditions but would exhibit relatively greater performance deficits in the across-channel conditions. A subsidiary aim was to determine whether, in normal-hearing listeners, the across-channel effects previously observed for minimal-duration standard gaps also existed for relatively long standard gaps. Two experiments were undertaken, one dealing with monaural conditions and one dealing with dichotic conditions. The monaural results indicated that across-frequency GDD was poorer than isofrequency GDD, even for the longer gap durations of 35 and 250 ms examined here. However, the results showed no effect of hearing loss on GDD. Rather, GDD appeared to be sensitive to listener age, with younger listeners showing better performance in both within-channel and across-channel conditions. In addition, both within-channel and across-channel performance was sensitive to the duration of the leading gap marker. Finally, the pattern of dichotic "across-ear" performance was similar, but not equivalent, to that of monaural across-frequency performance.

Adult↗
PubMed2001

Quantitative volumetry in patients with carotid disease--effects of acetazolamide.

The intracranial effects of acetazolamide on flow velocities can be monitored noninvasively by transcranial Doppler (TCD) sonography. Extracranial volume flow changes can now reliably be measured with color duplex M-mode systems. The authors tested the volumetric effects of acetazolamide in patients with high-grade unilateral carotid disease to quantify the amount of flow changes. Patients in group 1 had a high-grade > 70% internal carotid artery (ICA) stenosis, without collateral flow through the ophthalmic artery (OA). Patients with occluded ICA were included in group 2 (patent OA collateralization) or group 3 (no OA collateralization) (n = 6 per group). In group 1, common carotid artery (CCA) volume flow in the stenotic (normal contralateral) side increased from 271 (388) ml/min by 52 (54%) with 1 g aceta-zolamide intravenously. Simultaneously, middle cerebral artery (MCA) flow velocities increased from 54 (56) cm/s by 47 (53%). In group 2, extracranial volume flow increased from 166 (444) ml/min by 19 (52)%. MCA flow velocities increased from 43 (65) cm/s by 13 (30)%. In group 3, volume flow increased from 159 (467) ml/min by 2 (46)%. Intracranial flow velocities rose from 49 (54) cm/s by 27 (41)%. Volume flow data showed the expected decline in patients with high-grade ICA stenosis and even more pronounced in patients with occlusion of the vessel. Cerebral reserve capacity was less sufficient in patients with a patent OA, despite an additional supply of 30 ml/min, indicating a hemodynamically critical situation.

Acetazolamide↗
PubMed2001

A comparison of threshold estimation methods in children 6-11 years of age.

Estimating detection threshold for auditory stimuli in children can be problematic because of lapses in attention and the time limits usually imposed by scheduling restrictions or fatigue. Data reported here were collected to compare the stability of threshold estimation procedures in testing children ages 6 to 11 in a three-alternative, forced-choice paradigm. Stimuli consisted of a 1-kHz tonal signal and a Gaussian noise masker, bandpass filtered between 500-2,000 Hz and presented at 25-dB spectrum level. The signal was either presented for 400 ms in the presence of a continuous masker (simultaneous masking) or for 10 ms just prior to a 400-ms masker (backward masking). For each masking paradigm the 79% correct threshold was assessed via each of three procedures: 3-down, 1-up adaptive staircase (Levitt), maximum likelihood estimation (MLE), and method of constant stimuli. Percent correct was measured at the end of the study for a signal 10 dB above the previously determined threshold in order to estimate the most appropriate psychometric function asymptote for fitting data collected via the method of constant stimuli. Both the MLE and Levitt procedures produced equally stable threshold estimates for both conditions and age groups. This was the case despite considerable variability in backward-masking thresholds.

Adult↗
PubMed2001

Gap detection for similar and dissimilar gap markers.

Detection thresholds for temporal gaps between markers of dissimilar frequency are usually elevated with respect to thresholds for gaps between markers of similar frequency. Because gaps between markers of dissimilar frequency represent both a spectrally based perceptual discontinuity as well as a temporal discontinuity, it is not clear what factors underlie the threshold elevation. This study sought to examine the effects of perceptual dissimilarities on gap detection. The first experiment measured gap detection for configurations of narrow-band gap markers comprised of pure tones, frequency-modulated tones, and amplitude-modulated tones. The results showed that gap thresholds for frequency-disparate pure-tone markers were elevated with respect to isofrequency tonal markers, but that perceptual discontinuities between markers restricted to the same frequency region did not uniformly elevate threshold. The second experiment measured gap detection for configurations of markers where the leading and trailing markers could differ along the dimensions of bandwidth, duration, and pitch. The results showed that, in most cases, gap detection deteriorated when the bandwidth of the two markers differed, even when the spectral content of the narrower-band marker was completely subsumed by the spectral content of the wider-band marker. This finding suggests that gap detection is sensitive to spectral dissimilarity between markers in addition to spectral discontinuity. The effects of marker duration depended on the marker bandwidth. Pitch differences across spectrally similar markers had no effect.

Adult↗
PubMed1999

Development of adult-like performance in backward, simultaneous, and forward masking.

Some researchers have argued that specific language impairment (SLI) is associated with deficits in processing certain temporal aspects of auditory stimuli. One recent study (Wright et al., 1997) suggests that backward masking in particular poses a problem for children with SLI, as compared to simultaneous or forward masking. Interpretation of this finding is complicated by the fact that very little is known about the development of normal, adult-like performance in these masking paradigms. The study reported here examined performance for children 5-11 years old on forward, simultaneous, and backward masking and compared their performance to that of adults. The data show a trend for improvement in performance with age in all three masking paradigms. There was no evidence for later or more gradual improvement in performance on the backward-masking paradigm. However, backward-masking thresholds were more variable than those in the other conditions and were subject to greater individual differences, even in the adult data set. Manipulation of masker bandwidth yielded no evidence for more adult-like performance in the child data with the wider bandwidth masker. Additional data collected on two naive adult observers show a marked improvement in backward-masking performance over time, suggesting that detection with these stimuli might be particularly subject to practice effects.

Adult↗
PubMed1999

Modulation gap detection: effects of modulation rate, carrier separation, and mode of presentation.

Modulation gap detection (MGD) is a procedure that measures the sensitivity to an interruption in the modulation pattern imposed upon one or more carrier frequencies. The MGD task was developed to test conditions where a temporal event traverses frequency, but without a concomitant interruption in the spectral continuity of the stimulus. This contrasts with across-frequency gap detection where there is an inherent spectral discontinuity associated with the temporal gap, and where there is a marked decline in performance when the markers of the temporal gap are widely separated in frequency. The purpose of this study was to test the hypothesis that a wideband temporal analysis will be facilitated if there exists a spectral continuity throughout the temporal event. Experiment 1 established the procedure of MGD and indicated that a modulation rate of 8 Hz was optimal for the task. Experiment 2 showed that performance declined markedly when the carrier frequencies of the modulation markers were widely separated in frequency. This finding indicates that spectral continuity across the temporal event is not a sufficient prerequisite for the auditory system to undertake a wideband temporal analysis. Experiment 3 revealed that dichotic MGD also results in poor performance, similar to that seen for widely separated carrier frequencies in the monaural case. This supports the hypothesis that the "channels" across which temporal events are poorly processed do not necessarily correspond to peripheral frequency channels.

Audiometry, Pure-Tone↗
PubMed1999

Influence of acetazolamide and CO2 on extracranial flow volume and intracranial blood flow velocity.

BACKGROUND AND PURPOSE: The vasomotor response can be tested by means of transcranial Doppler sonography. If a constant vessel diameter is assumed, the flow velocity changes will reflect blood flow volume changes. This hypothesis is difficult to verify. Simultaneous assessment of intracranial flow velocity and extracranial flow volume changes may solve this problem. METHODS: We tested vasomotor response in 32 volunteers (age, 42+/-18 years) with 5% CO2. Acetazolamide (1 g) was tested in 15 volunteers (age, 28+/-8 years). To evaluate drug-dependent flow changes in the external carotid artery territory, acetazolamide was administered in 7 patients with unilateral occlusion of the internal carotid artery without evidence of collateralization through the ophthalmic artery (age, 67+/-12 years). Simultaneous recording included measurements of flow volume in the common carotid arteries (M-mode color duplex system) and flow velocity in the middle cerebral arteries. RESULTS: With CO2 and acetazolamide, intracranial flow velocity increased by 31% and 39%, respectively, with a simultaneous increase of common carotid artery flow volume of 47% and 50%, respectively. No change in extracranial flow volume was observed in patients with an occluded internal carotid artery. CONCLUSIONS: These data show not only the expected increase of flow velocity in the middle cerebral artery but also suggest an increase in cross-sectional vessel diameter of 6% and 4% with CO2 and acetazolamide, respectively. It remains unresolved whether this observation is due to a direct effect of the drug on the vessel walls or is simply pressure dependent.

Acetazolamide↗
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

The effects of different envelope patterns and uncertainty for the detection of a tone added to SAM complex tonal maskers.

Thresholds for the detection of a tone added in-phase to the carrier of a fully modulated SAM tone were measured. In some conditions the signal was added to a single SAM tone, and in other conditions the signal was added to the sum of three or more SAM tones. Level equalization ensured that the addition of the tonal signal did not lead to increases in energy. When multiple SAM tone maskers were used, a small number of reproducible maskers were tested, each masker being composed of SAM tones with a variety of relative modulator phases. The maskers were either fixed across intervals and trials, roved across trials but fixed across intervals, or randomly chosen across both intervals and trials. The frequency separation between the signal-centered and off-frequency SAM tones was also varied. For small signal-centered/off-frequency SAM tone frequency separations, a separation ratio of 1.3, thresholds in the fixed condition depend on the relative modulator phases, and a simple mixture model reasonably predicted thresholds in the roving condition based on thresholds in the fixed condition for two of the three observers. For signal-centered/off-frequency SAM tone frequency separation factor of 1.68, effects of relative modulator phases were not obtained. Thresholds in the target-alone condition were generally superior to thresholds measured with the comodulated masker. Comodulated thresholds were better than target-alone thresholds only when level equalization was not used, and so the addition of the signal led to increases in level.

Acoustic Stimulation↗
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 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

Effects of modulator phase for comodulation masking release and modulation detection interference.

In an effort to evaluate the importance of across-frequency comparisons of envelope patterns in comodulation masking release (CMR) experiments and to compare joint effects of target-masker frequency separation for both CMR and modulation detection interference (MDI) tasks, thresholds were measured for three tasks. These tasks were: (a) the detection of sinusoidal amplitude modulation (SAM) of a tone, (b) the detection of a reduction in the modulation depth of a fully modulated SAM tone, and (c) the detection of a tone added to a narrow band of noise. Thresholds were obtained for the target alone and for the target presented with two maskers. For the detection of SAM, thresholds did not depend on whether the modulation patterns of the target and masker elements were the same or random. For the latter two tasks, modulator phase effects were apparent for target-masker frequency separations less than 1-2 oct. In contrast, past work has shown that observers can compare modulator envelope phases across frequency separations larger than 1-2 oct [Strickland et al., J. Acoust. Soc. Am. 86, 2160-2166 (1989); Yost and Sheft, J. Acoust. Soc. Am. 85, 848-857 (1989)]. In a second experiment, thresholds for the detection of SAM were obtained after prolonged exposure to a fully modulated SAM tone. For four of the five observers, modulation-rate specific adaptation was obtained for test/adapting carrier-frequency separations approaching 2 oct below and 1 oct above the adaptor.

Auditory Perception↗
PubMed1996

The effects on comodulation masking release of systemic variations in on- and off-frequency masker modulation patterns.

Detection thresholds were obtained for a 500-Hz tone added to a masker comprised of an amplitude-modulated tone centered at the signal frequency (on-frequency masker) and an array of amplitude modulated tones centered at 300, 700, 800, 900, 1000, and 1100 Hz (off-frequency maskers). The shapes of the amplitude modulation patterns of the on- and off-frequency maskers were either matched or mismatched. In the shape-matched conditions the on- and off-frequency masker modulation patterns were the same, either sinusoidally or square-wave amplitude modulated. In the shape-mismatched conditions, the on-frequency masker was sinusoidally amplitude modulated and the off-frequency maskers were square-wave amplitude modulated. The rate of modulation was either 10 or 20 Hz, and the duty cycle of square-wave modulation was systemically varied. The relative phases of the on- and off-frequency modulators were either in-phase, out-of-phase, or random-phase. Comodulation masking release (CMR) was defined as the difference between thresholds in the in-phase and random-phase conditions. CMRs as large as 12 dB were obtained for the shape-matched as well as the shape-mismatched conditions. Thresholds in the out-of-phase condition were on average 2.6 dB higher than those in the random-phase condition. Results are consistent with a cued listening model where off-frequency modulation minima trigger sampling at the output of the auditory filter centered on the signal frequency.

Adult↗
PubMed1991

Weight change in depression: influence of "disinhibition" is mediated by body mass and other variables.

The direction of weight change (gain or loss) in depression has recently been found to be a stable characteristic of patients across depressive episodes. A search for determinants of the direction of weight change revealed two candidates: the body mass index (BMI) (weight in kilograms/height in meters squared) and a psychological variable, "disinhibition" of dietary restraint. The present study, of 68 patients with a history of recurrent depression, found a significant correlation between BMI and weight change; in other words, heavier persons were more likely to gain weight if depressed. There was also a correlation between "disinhibition" and weight change. "Disinhibition" correlated with BMI and, when controlled for BMI, age and sex, the correlation between "disinhibition" and weight change fell to insignificance. We conclude that BMI along with age and sex mediated the correlation between "disinhibition" and weight change.

Appetite↗