Biomedical subjects

F Wightman

Publications and source records attributed to F Wightman.

At least 19 recordsLinked to original sources

PubMed2005

A randomised controlled trial of oral zinc on the immune response to tuberculosis in HIV-infected patients.

SETTING: The National HIV Unit, Singapore. OBJECTIVE: To test whether zinc supplementation improves the immune response to tuberculosis in HIV-positive patients. DESIGN: A double-blind, randomised, placebo-controlled trial of 28 days of oral zinc sulphate (50 mg of elemental zinc) or placebo in stable adult HIV-positive patients receiving antiretroviral therapy with a CD4 count <200 cells/microl. METHODS: IFN-gamma response to mycobacterial antigen stimulation, CD4/8 cell count, lymphocyte subsets, T-cell receptor excision circle (TREC) levels and viral load were measured at baseline and day 28. RESULTS: Thirty-two patients received zinc and 34 placebo. There was no significant change in the IFN-gamma response to human PPD stimulation in the zinc or placebo groups (placebo baseline: 0.42 +/- 1.03, day 28: 0.84 +/- 1.21 IU/ml, zinc baseline: 1.26 +/- 2.41, day 28: 1.39 +/- 1.88 IU/ml, P = 0.31 between groups), nor any of the other mycobacterial antigens tested. There were no changes in absolute CD4/8 cell levels or other lymphocyte subsets, TREC or viral load. Baseline zinc levels were normal in 62/66 (93.9%) patients. CONCLUSIONS: We found no evidence for recommending pharmacological supplementation with oral zinc in HIV-positive patients without zinc deficiency.

Administration, Oral↗

PubMed2001

Children's detection of pure-tone signals with random multitone maskers.

Preschoolers and adults were asked to detect a 1000-Hz signal, which was masked by a multitone complex. The frequencies and amplitudes of the components in the complex varied randomly and independently on each presentation. A staircase, cued two-interval, forced-choice procedure disguised as a "listening game" was used to obtain signal thresholds in quiet and in the presence of the multitone maskers. The number of components in the masker was fixed within an experimental condition and varied from 2 to 906 across experimental conditions. Thresholds were also measured with a broadband noise masker. Eight preschool children and eight adults were tested. Although individual differences were large, among both adults and children, there was little difference between the groups in the mean amount of masking produced by the maskers with large numbers of components (400 and 906). There was also a small but significant difference between adults and children in the mean amount of masking produced by the broadband noise. The difference between the groups was much larger with smaller numbers of components. Data obtained from the adults were basically similar to that previously reported [cf. Neff and Green, Percept. Psychophys. 41, 409-415 (1987); Oh and Lutfi, J. Acoust. Soc. Am. 104, 3489-3499 (1998)]: maskers comprised of 10-40 components produced as much as 30 to 60 dB of masking in some, but not all listeners. Those same maskers produced larger amounts of masking (70-83 dB) in many of the preschool children, although, as in the adult group, individual differences were large. The component-relative-entropy (CoRE) model [Lutfi, J. Acoust. Soc. Am. 94, 748-758 (1993)] was used to describe the differences in performance between the children and adults. According to this model the average child appears to integrate information over a larger number of auditory filters than the average adult.

Adult↗

PubMed1998

Of vulcan ears, human ears and 'earprints'.

Explore the source record for details and available documents.

Adaptation, Physiological↗

PubMed1995

Effects of signal and masker uncertainty on children's detection.

This paper reports the results of two experiments that examined the effects of signal and masker uncertainty on preschool-age children's and adults' detection of tonal signals in noise maskers. In Experiment 1 (signal uncertainty) the signal was randomly at 501 or 2818 Hz. The majority of the adult listeners showed a slight decrement in performance consistent with an ability to monitor both frequencies simultaneously. The majority of the children, however, showed no decrement in performance, suggesting that the children may not have focused attention at the signal frequency even when it was fixed. In Experiment 2 (masker uncertainty), random-frequency, random-level, tonal distracters were added to each interval of the 2 alternative-forced-choice (2afc) procedure. The effect of masker uncertainty was much larger than that of signal uncertainty. For most of the adult listeners and some of the children, the distracters produced higher thresholds (on average by 10 dB) and shallower psychometric function slopes. For most of the children, thresholds increased by 20 dB or more and psychometric functions were often nearly flat.

Adult↗

PubMed1994

Psychometric functions for children's detection of tones in noise.

This article reports the results of an experiment that used a two-alternative forced-choice task to measure the ability of 3- to 5-year-old children to detect 501 Hz, 1000 Hz, and 2818 Hz sinusoids in noise. Psychometric functions were fit to each individual's data, and thresholds (signal level required for 75% correct) were interpolated from the fitted functions. Results showed that, on average, the children's thresholds were higher and the slopes of their psychometric functions were shallower than those of the adults. However, the between-subjects variability in the children's data was large, and the performance of many individual children was not well described by group mean performance. One-third of the children produced thresholds that were elevated by an average of 10 dB but psychometric function slopes that were adult-like. Another one-third of the children produced thresholds that were elevated relative to those of the adults by an average of 20 dB and psychometric function slopes that were very shallow. The data from a smaller group of children showed large variability in psychometric function slope and threshold, and for a very few children performance was at chance regardless of the signal level. A replication of the study several months later showed that for most listeners the individual patterns of performance persisted over time.

Acoustic Stimulation↗

PubMed1992

Spectral pattern discrimination by children.

This research measured the ability of 47 children, aged 4-9 years, to use spectral shape cues to discriminate among random-intensity sounds. The children were tested in forced-choice paradigms that were embedded in a video game format. Two classes of sounds were studied: tonal complexes with sinusoidally rippled amplitude spectra, and synthetic speech sounds (isolated vowels and consonants). The discriminability of the sounds was measured both in quiet and in a background of wide-band noise. Although the intersubject variability in performance was high, especially among the youngest children, the results revealed a substantial age effect. For both classes of sounds, the performance of the younger children was significantly poorer than the performance of an adult control group. However, there was no evidence in the data that the masking effect of the noise was greater for the children than for the adults.

Adolescent↗

PubMed1989

Frequency resolution in children.

The auditory frequency resolving ability of preschool children, school-aged children, and adults was assessed in a standard forced-choice masking experiment. Thresholds for pure-tone signals at 500 Hz, 2000 Hz, and 4000 Hz were obtained in two masking conditions. In one condition, the masker was a 4000-Hz-wide band of noise centered at the signal frequency; in the other, there was a notch in the noise spectrum, approximately one-half octave wide and 50 dB deep, centered at the signal frequency. Frequency resolving ability was inferred from the difference in signal threshold between the two masking conditions. The adaptive forced-choice psychophysical procedure was embedded in a video game in order to obtain rigorous psychophysical data within the attentional limits of young children. This procedure produced data from children as young as 3 years old that were qualitatively indistinguishable from adult data. However, the threshold estimates from the children were more variable from run to run than were the estimates obtained from adults. The mean data from this experiment suggest that frequency resolving ability improves at all frequencies with increasing age.

Adult↗

PubMed1989

Temporal resolution in children.

The auditory temporal resolving power of young children was measured using an adaptive forced-choice psychophysical paradigm that was disguised as a video game. 20 children between 3 and 7 years of age and 5 adults were asked to detect the presence of a temporal gap in a burst of half-octave-band noise at band center frequencies of 400 and 2,000 Hz. The minimum detectable gap (gap threshold) was estimated adaptively in 20-trial runs. The mean gap thresholds in the 400-Hz condition were higher for the younger children than for the adults, with the 3-year-old children producing the highest thresholds. Gap thresholds in the 2,000-Hz condition were generally lower than in the 400-Hz condition and showed a similar age effect. All the individual adaptive runs were "adult-like," suggesting that the children were generally attentive to the task during each run. However, the variability of threshold estimates from run to run was substantial, especially in the 3-5-year-old children. Computer simulations suggested that this large within-subjects variability could have resulted from frequent, momentary lapses of attention, which would lead to "guessing" on a substantial portion of the trials.

Attention↗

PubMed1980