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Biomedical subjects

W D Ward

Publications and source records attributed to W D Ward.

At least 19 recordsLinked to original sources
PubMed1991

The role of intermittence in PTS.

Exposure of chinchillas to noise that is continuous results in auditory damage that is a function of the total energy of the exposure, provided that a critical exposure is not exceeded. Breaking a continuous exposure into 45 exposure periods given once a day Monday through Friday for 9 weeks (an interrupted exposure) is shown to result in a slight reduction in damage, but breaking each of the 45 daily exposures into short noise bursts presented at regular intervals (interrupted and intermittent exposures) reduces the damage more significantly. The shorter the noise bursts, the greater will be the reduction in damage. Too few data are available to establish a principle that will predict correctly the amount of reduction afforded by a particular temporal pattern; while the "equal energy" principle predicts no reduction at all, the "mean level" principle derived from studies of temporary threshold shifts (e.g., a noise at 80 dB half the time and at 100 dB half the time has a mean level of 90 dB and will have the same effect as a continuous 90-dB noise) predicts too much reduction.

Animals↗
PubMed1990

The role of subject verbalization in generalized correspondence.

We examined the role of subject verbalization in the generalization of verbal-nonverbal correspondence. Twelve kindergarten children underwent correspondence training (subject verbalization) or received reinforcement for performing an experimenter-selected behavior (experimenter verbalization). A reversal design, along with the introduction of a multiple baseline design across behaviors, was used to assess functional relations. Pupils who received correspondence training demonstrated greater generalization. Our findings suggest that subject verbalization may be necessary to accomplish generalized correspondence.

Attention↗
PubMed1989

Comments on "The Growth of and Recovery from TTS in Human Subjects Exposed to Impact Noise" [J. Acoust. Soc. Am. 85, 1681-1690 (1989)].

This letter disputes the contention that the growth of temporary threshold shift (TTS) with time can be adequately described by Gompertz functions. The similarity between TTS growth functions in high levels of impact and of continuous noise is stressed, a similarity that leads to the proposition that some sort of peak-limiting action that occurs at the stapes serves to protect the cochlea in the 120-dBA region.

Auditory Threshold↗
PubMed1983

The American Medical Association/American Academy of Otolaryngology formula for determination of hearing handicap.

The main problem in attempting to estimate auditory handicap from easily measured indices such as pure-tone sensitivity or intelligibility scores for numbers, words or sentences is that no criterion to establish validity has received wide acceptance. Even though few would disagree with the definition of handicap accepted by the American Medical Association: 'the disadvantage imposed by an impairment sufficient to affect the individual's efficiency in the activities of daily living', this definition is so vague that it is of little practical value. Consequently, all formulae to rate handicap are based on assumptions of a more or less arbitrary nature. A dozen such assumptions are shown to underly the formula of the American Medical Association/American Academy of Otolaryngology.

Age Factors↗
PubMed1979

Alteration of oxidative enzymes (LDH and MDH) in perilymph after noise exposure.

Chinchillas were exposed to noise (123 dB, 1/2 h, 700--2800 Hz). The activity of lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) was studied immediately after exposure or 1, 7, 14, 21, or 28 days later. LDH activity in perilymph doubled immediately after exposure, gradually decreasing to control values in about a month. The activity of MDH not only doubled immediately after the exposure but continued to rise for at least another 24 h, reaching a peak value of 3.5 times normal at 24 h. The activity was still 1.6 times normal even after a month of recovery. The enzyme activity of serum and CSF remained within the control range throughout the experimental period except for an initial increase of serum enzyme activity due to anesthetic. The results demonstrate that the morphological changes induced by a noise exposure that is known to produce permanent threshold shift (PTS) are reflected in a significant elevation of oxidative enzymes in perilymph. Possible mechanisms of the elevation of enzymes in perilymph are discussed.

Animals↗
PubMed1978

Categorical perception--phenomenon or epiphenomenon: evidence from experiments in the perception of melodic musical intervals.

Categorical perception was investigated in a series of experiments on the perception of melodic musical intervals (sequential frequency ratios). When procedures equivalent to those typically used in speech-perception experiments were employed, i.e., determination of identification and discrimination functions for stimuli separated by equal physical increments), musical intervals were perceived categorically by trained musicians. When a variable-step-size (adaptive) discrimination procedure was used, evidence of categorical perception (in the form of smaller interval-width DL's for ratios at identification category boundaries than for ratios within categories), although present initially, largely disappeared after subjects had reached asymptotic performance. However, equal-step-size discrimination functions obtained after observers had reached asymptotic performance in the adaptive paradigm were not substantially different from those initially obtained. The results of other experiments imply that this dependence of categorical perception on procedure may be related to differences in stimulus uncertainty between the procedures. An experiment on the perception of melodic intervals by musically untrained observers showed no evidence for the existence of "natural" categories for musical intervals.

Humans↗