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Biomedical subjects

B A Wright

Publications and source records attributed to B A Wright.

At least 19 recordsLinked to original sources
PubMed2000

Continuity and change in the evaluation of ideal and acceptable body sizes across a wide age span.

OBJECTIVE: Continuity and change in the evaluation of ideal and acceptable body sizes across a wide subject age span were examined. METHOD: Ratings of ideal and socially acceptable body sizes were elicited from 303 children, 427 adolescents, 261 young adults, and 326 middle-age adults. Line drawing arrays of babies, children, young adults, middle-age, and older adults were portrayed, ranging in size from very thin to very obese. RESULTS: All subject groups selected, in all arrays, similar ideal body sizes, rated sizes in the midrange of fatness as socially acceptable, and were least accepting of very thin and obese body sizes. Tolerance for body size variations increased with subject age. DISCUSSION: Continuity throughout a wide subject age span was observed in evaluations of body sizes. However, adults were more accepting of body size variations than younger subjects, especially children. Implications of endorsing midrange body sizes for the fashion industry are discussed.

Adolescent↗
PubMed1999

Strategies used to detect auditory signals in small sets of random maskers.

Detection performance for a masked auditory signal of fixed frequency can be substantially degraded if there is uncertainty about the frequency content of the masker. A quasimolecular psychophysical approach was used to examine response strategies in masker-uncertainty conditions, and to investigate the influence of uncertainty when the number of different masker samples was limited to ten or fewer. The task of the four listeners was to detect a 1000-Hz signal that was presented simultaneously with one of ten ten-tone masker samples. The masker sample was either fixed throughout a block of two-interval forced-choice trials or was randomized across or within trials. The primary results showed that: (1) When the signal level was low and the masker sample differed between the two intervals of a trial, most listeners based their responses more on the presence of specific masker samples than on the signal. (2) The detrimental effect of masker uncertainty was clearly evident when only four maskers were randomly presented, and grew as the size of the masker set was increased from two to ten. (3) The slopes of psychometric functions measured with the same masker samples differed among the fixed and two random-masker conditions. (4) There were large differences in the influence of masker uncertainty across masker samples and listeners. These data demonstrate the great susceptibility of human listeners to the influence of masker uncertainty and the ability of quasimolecular investigations to reveal important aspects of behavior in uncertainty condition.

Adult↗
PubMed1998

Practice-related improvements in somatosensory interval discrimination are temporally specific but generalize across skin location, hemisphere, and modality.

This paper concerns the characterization of performance and perceptual learning of somatosensory interval discrimination. The purposes of this study were to define (1) the performance characteristics for interval discrimination in the somatosensory system by naive adult humans, (2) the normal capacities for improvement in somatosensory interval discrimination, and (3) the extent of generalization of interval discrimination learning. In a two-alternative forced choice procedure, subjects were presented with two pairs of vibratory pulses. One pair was separated in time by a fixed base interval; a second pair was separated by a target interval that was always longer than the base interval. Subjects indicated which pair was separated by the target interval. The length of the target interval was varied adaptively to determine discrimination thresholds. After initial determination of naive abilities, subjects were trained for 900 trials per day at base intervals of either 75 or 125 msec for 10-15 d. Significant improvements in thresholds resulted from training. Learning at the trained base interval generalized completely across untrained skin locations on the trained hand and to the corresponding untrained skin location in the contralateral hand. The learning partially generalized to untrained base intervals similar to the trained one, but not to more distant base intervals. Learning with somatosensory stimuli generalized to auditory stimuli presented at comparable base intervals. These results demonstrate temporal specificity in somatosensory interval discrimination learning that generalizes across skin location, hemisphere, and modality.

Adult↗
PubMed1998

Detection of sinusoidal amplitude modulation at unexpected rates.

The detectability of sinusoidal amplitude modulation at unexpected modulation rates was assessed using a probe-signal method. With this method, three listeners were led to expect a target modulation rate (4, 32, or 256 Hz) by presenting the signal most often at that rate, and sensitivity to modulation at six other unexpected rates between 4 and 256 Hz was measured via occasionally presented probe modulation rates. The modulation phase was random on each two-interval forced-choice trial and the overall level of the 500-ms broadband carrier was randomly varied between 55 and 75 dB SPL across intervals. The modulation depth at each rate was set so that the modulation was detected on about 90% of the trials when only that rate was presented. Performance at the unexpected rates depended upon the target rate. For the 4-Hz target, modulation at all rates was detected on about 80% of the trials. For the 32- and 256-Hz targets, unexpected modulation rates of 16 Hz and above were detected on 80%-90% of the trials, but modulation rates below 16 Hz were detected nearly at chance. The influence of expectation of modulation rate on the detection of sinusoidal amplitude modulation is not readily predicted by current models of modulation detection.

Adult↗
PubMed1997

Learning and generalization of auditory temporal-interval discrimination in humans.

The sensory encoding of the duration, interval, and order of different stimulus features provides vital information to the nervous system. The present study focuses on the influence of practice on auditory temporal-interval discrimination. The goals of the experiment were to determine (1) whether practice improved the ability to discriminate a standard interval of 100 msec bounded by brief 1 kHz tones from longer intervals, and, if so, (2) whether this improvement generalized to different tonal frequencies or temporal intervals. Learning was examined in 14 human subjects using an adaptive, two-alternative, forced-choice procedure. One hour of training per day for 10 d led to marked improvements in the ability to discriminate between the standard and longer intervals. The generalization of learning was evaluated by independently varying the spectral (tonal frequency) and temporal (interval) components of the stimuli in four conditions tested both before and after the training phase. Remarkably, there was complete generalization to the trained interval of 100 msec bounded by tones at the untrained frequency of 4 kHz, but no generalization to the untrained intervals of 50, 200, or 500 msec bounded by tones at the trained frequency of 1 kHz. Thus, these data show that (1) temporal-interval discrimination using a 100-msec standard undergoes perceptual learning, and (2) the neural mechanisms underlying this learning are temporally, but not spectrally, specific. These results are compared with those from previous investigations of learning in visual spatial tasks, and are discussed in relation to biologically plausible models of temporal processing.

Acoustic Stimulation↗
PubMed1997

Deficits in auditory temporal and spectral resolution in language-impaired children.

Between 3 and 6 per cent of children who are otherwise unimpaired have extreme difficulties producing and understanding spoken language. This disorder is typically labelled specific language impairment. Children diagnosed with specific language impairment often have accompanying reading difficulties (dyslexia), but not all children with reading difficulties have specific language impairment. Some researchers claim that language impairment arises from failures specific to language or cognitive processing. Others hold that language impairment results from a more elemental problem that makes affected children unable to hear the acoustic distinctions among successive brief sounds in speech. Here we report the results of psychophysical tests employing simple tones and noises showing that children with specific language impairment have severe auditory perceptual deficits for brief but not long tones in particular sound contexts. Our data support the view that language difficulties result from problems in auditory perception, and provide further information about the nature of these perceptual problems that should contribute to improving the diagnosis and treatment of language impairment and related disorders.

Analysis of Variance↗
PubMed1997

Detectability of simultaneously masked signals as a function of masker bandwidth and configuration for different signal delays.

Signal detectability was measured in three temporal conditions as a function of the bandwidth and configuration of simultaneous maskers that either did or did not spectrally overlap the signal. The 20-ms signal was 250 Hz wide and was centered at 2500 Hz (fs). Although there were marked individual differences, performance was typically poorer when signal onset came 1 ms rather than 250 ms after the onset of a 420-ms masker, and poorest when signal onset came 1 ms after the onset of a 23-ms masker. The results support the idea that two separate across-channel processes contribute to temporal changes in signal detectability. One process contributes to the improvement observed as signal onset is delayed from masker onset, and its influence is reduced by the presence of masking components at fs only when the masker extends exclusively below fs. The other process is associated with the improvement observed as masker offset is delayed from signal offset, and its influence is reduced by the presence of masking components at fs when the masker extends exclusively above, or both below and above fs. Both of these processes are primarily activated by frequencies ranging from 0.6 to 0.8fs and 1.2 to 1.4fs. The data also demonstrate that the measured critical bandwidth narrows as signal onset is delayed from masker onset.

Auditory Perception↗
PubMed1996

Auditory filter asymmetry at 2000 Hz in 80 normal-hearing ears.

Auditory filter asymmetry, bandwidth, dynamic range, and efficiency was measured at 2000 Hz in both ears of 40 naive, normal-hearing adults, counterbalanced for sex and initial ear tested. The filters were measured with 200-ms tonal signals temporally centered in 300-ms maskers. The maskers were notched noises presented at a spectrum level of 40 dB SPL. Quiet thresholds for the signal were also obtained. The distributions of the measured variables and correlations between them are reported. The average filter was nearly symmetric but the most common filters had steeper upper slopes. The shapes of the two sides of the filter were independent. Filter asymmetry was not correlated with the equivalent rectangular bandwidth (ERB), and quiet threshold was not consistently correlated with the dynamic range of the filter or with ERB. The mean ERB was 255 Hz.

Adolescent↗
PubMed1996

Correlated individual differences in conditions used to measure psychophysical suppression and signal enhancement.

Two-tone suppression and notched-noise signal enhancement (overshoot) were measured at 1000 Hz using standard procedures in 40 normal-hearing, naive adults, counterbalanced for sex, listening ear, and testing order. The threshold range across subjects for the same condition often exceeded 30 dB. In the suppression conditions, for some subjects the 20-ms forward-masked signal was as much as 15 dB easier to detect when the total masker (1000 Hz) and tonal suppressor (1150 Hz) were presented together, than when the masker was presented alone, indicating suppression. For other subjects, however, presenting the masker and suppressor together increased thresholds by as much as 13 dB, indicating additional masking. On average, adding the suppressor to the masker increased threshold by 0.6 dB. In the enhancement conditions, for every subject the 20-ms signal was harder to detect when it was presented at the onset of a 500-ms notched-noise masker (notch width: 1000 Hz) than when signal onset was delayed by 400 ms, and was hardest to detect when the signal and masker were gated on and off together for 20 ms. The average thresholds were 7 and 19 dB higher for the two conditions in which the signal was presented at masker onset than for the condition in which the signal was presented after a delay, indicating signal enhancement. The thresholds in all of the listening conditions appeared to be primarily determined by a single factor. However, it is not clear whether the best designation for this factor would be sharpness of frequency tuning or across-channel inhibitory strength.

Adolescent↗
PubMed1996

Nova Scotia Breast Screening Program experience: use of needle core biopsy in the diagnosis of screening-detected abnormalities.

PURPOSE: To evaluate a mammography screening program that uses a multidisciplinary team approach and needle core biopsy. MATERIALS AND METHODS: A total of 10,000 asymptomatic women (aged 40-74 years) underwent screening in the Nova Scotia Breast Screening Program between June 1991 and April 1994. Women aged 50-69 years were the target group. All mammograms were read by one of four radiologists. Patients with abnormal screening findings underwent work-up, which included needle core biopsy, at one of two diagnostic centers. RESULTS: Of 10,000 women, 2,794 were aged 40-49 years; 4,097, 50-59 years; 2,941, 60-69 years; and 168, 70-74 years, with 3.9, 6.4, 12.2, and 23.8 cancers detected per 1,000 patients, respectively. The overall rate was 7.7 cancers detected per 1,000 patients. Abnormalities were detected at screening in 838 patients (8.4%), 181 of whom underwent open surgery, with malignancy diagnosed in 77 (42%). Sixty-one (79%) of 77 patients had stage 0 or I cancer. In 43 (72%) of 60 patients in whom node status was assessed, findings were negative. CONCLUSION: A screening program with needle core biopsy and a multidisciplinary team approach to diagnosis is effective.

Adult↗
PubMed1995

Detectability of simultaneously masked signals as a function of signal bandwidth for different signal delays.

The improvement in signal detectability as signal onset is delayed from masker onset was measured as a function of signal bandwidth for wideband and notched-noise maskers. The signal was centered at 2500 Hz. In two conditions, the 20-ms signal was gated 1 or 250 ms after the onset of a 420-ms masker. Although there were marked individual differences, the signal was consistently more difficult to detect in the short-delay than in the long-delay condition. The difference in detectability decreased as signal bandwidth increased and was similar in magnitude across the masker types. This result indicates that an across-channel process contributes to the improvement in detectability as the signal delay is increased, because the masking components at the signal frequency in the wideband masker exerted very little influence on the size of the effect. In a third condition, the signal was gated 1 ms after the onset of a 23-ms masker. The signal was hardest to detect in this burst condition, and performance varied differently as a function of signal bandwidth in this than in the other two conditions, particularly for the notched-noise maskers. This outcome suggests the presence of a second across-channel process that is sensitive to masker offsets, especially when there are no masking components at the signal frequency. Finally, the pattern of results obtained across the three conditions using the wideband masker was consistent with the idea that the critical bandwidth narrows as the signal is delayed from masker onset.

Auditory Perception↗
PubMed1995

Detecting signals of unexpected or uncertain durations.

Expectation of signal duration influences the signal detectability. This is demonstrated in two experiments in which percent correct was measured for both tonal and noise signals whose durations were either unexpected or uncertain. In both experiments, the signal at each duration was set to have a d' of about 1.5 when that duration was presented alone and expected. When the six subjects were led to expect a short- or a long-duration signal using the probe-signal method, the detectability of signals decreased to near chance as the signal duration deviated from the expected value (experiment 1). When the subjects were led to expect a range of durations, the detectability was only slightly worse than when each signal was presented alone (experiment 2). Those results suggest that listeners adjust their temporal-integration intervals according to the demand of the specific task. Finally, the results obtained with the noise signal were analyzed using the multiple-look model and a modified energy-detector model. Assuming that the integration interval is matched to the expected signal duration, both models predict the detection of signals having unexpected durations reasonably well. Both models, however, fail to predict the small effect of duration uncertainty.

Audiometry, Pure-Tone↗
PubMed1994

Improving the detectability of a brief tone in noise using forward and backward masker fringes: monotic and dichotic presentations.

A brief tonal signal simultaneously masked by a brief noise burst became easier to hear when the masker duration was increased. The signal was a 1000-Hz tone, 4 ms in duration; the masker was a wideband noise having a spectral notch 1400 Hz wide centered at 1000 Hz. Compared to performance with a 22-ms burst masker, average detection threshold across five subjects improved by 15 dB when a 150-ms masker "fringe" preceded the signal (forward fringe), and by 9 dB when the masker fringe followed the signal (backward fringe). Little improvement was observed in either condition when the fringe was presented to the ear contralateral to the signal/burst complex. However, when the fringe was presented to both ears and the signal/burst complex to just one ear, the forward fringe was about as helpful as when the stimuli were presented monotically, but the benefit of the backward fringe was substantially reduced. The backward-fringe advantage was restored by reducing the level, or delaying the onset, of the contralateral component of the fringe. The results suggest that the forward-fringe advantage is a robust phenomenon that is largely insensitive to input to the contralateral ear. In contrast, the backward-fringe advantage appears to be a fragile effect that can be affected by inputs from both ears.

Acoustic Stimulation↗
PubMed1994

Detection of unexpected tones with short and long durations.

The detectability of short and long unexpected tones masked by a continuous wideband noise was assessed using a probe-signal method. This method leads the listener to expect a target frequency by presenting the signal most often at that frequency, and only occasionally at other unexpected probe frequencies. The probe-signal contour (percent correct as a function of probe frequency) was considerably broader with 5-ms than with 295-ms signals. However, auditory filter shapes measured using the notched-noise technique were very similar for those two signal durations, indicating that the results obtained in the probe-signal conditions do not simply reflect peripheral frequency selectivity. Further supporting this interpretation, probe tones having the same frequency but a different duration from the target were poorly detected. It is proposed that the subject listens through a time-frequency window whose location and shape in the time-frequency plane is determined by the duration and frequency of the target.

Acoustic Stimulation↗
PubMed1994

Detection of unexpected tones in gated and continuous maskers.

The effect of gating a wideband masker on the detectability of tones having unexpected frequencies was assessed using a probe-signal method. This method leads the listener to expect a target frequency by presenting the signal most often at that frequency, and measures sensitivity to other unexpected frequencies via occasionally presented probe tones. For 295-ms signals, the probe-signal contours (percent correct as a function of probe frequency) of two of four subjects were considerably broader for a 295-ms masker than for a continuous masker. For 5-ms signals, the probe-signal contours of four of five subjects were quite broad and similar for both gated and continuous maskers. When the probe-signal contours were expressed as the attenuation in decibels of the probes, the resulting "probe-signal filters" were frequently broader than auditory filters measured using notched noise in the same subjects. This suggests that subjects may monitor multiple auditory filters under some conditions in the probe-signal task. Signal threshold tended to be higher for conditions showing wider probe-signal filters, indicating a potential link between changes in signal threshold due to masker gating and the number of frequency channels that are monitored.

Acoustic Stimulation↗