Biomedical subjects

R G Karzon

Publications and source records attributed to R G Karzon.

7 recordsLinked to original sources

PubMed1991

Validity and reliability of tympanometric measures for pediatric patients.

Sensitivity and specificity of static acoustic admittance (SAA) and tympanometric width (TW) were assessed for 116 pediatric patients. Otologic examination was the validation criterion. Reliability of immediate repeat tympanometric measures (SAA, TW, peak pressure, and estimate of ear canal volume) was also evaluated. A statistically significant change in SAA, with a larger SAA on measure two than measure one, was observed. No significant change across the two sequential measures was observed for TW, peak pressure, or the estimate of ear canal volume. The sensitivity and specificity data collected are discussed with respect to assisting clinicians in selecting tympanometric criteria suitable to their own clinical situation.

Acoustic Impedance Tests↗

PubMed1990

Individual differences in auditory electric responses. III. A replication, with observations of individual vs. group characteristics.

In the first two reports in this series (Lauter & Loomis, 1986, 1988) we presented data on repeated-measures testing with auditory brainstem responses (ABRs) for a group of 7 normal young adults. In this paper, we report data for an additional group of 8 young adults, which replicate the patterns for both latency and amplitude stability observed in the first group, in spite of a number of procedural differences between the two studies. Examples are also presented from both groups illustrating the effects of individual-subject characteristics on group characteristics. Results indicate that ABR latency-variability patterns based on 8-week series are quite different from subject to subject, including individual peculiarities in the pattern of responses according to ear-of-presentation, and the detail of these differences may both contribute to and be obscured by the group within-subject calculations. In contrast, ABR amplitude-variability patterns are much more similar across individuals and ear-of-presentation, most often taking the form of a 'W-shaped' function, with greater consistency at peaks I, III, and V, compared with peaks II and IV.

Acoustic Stimulation↗

PubMed1990

Individual differences in auditory electric responses: comparisons of between-subject and within-subject variability. IV. Latency-variability comparisons in early, middle, and late responses.

In this series of reports to date (Lauter & Loomis, 1986, 1988; Lauter & Karzon, 1990 a & b) we have described patterns of relative variability observed in latency and amplitude of auditory brainstem responses (ABRs) collected in a repeated-measures within-subjects design testing two groups of neurologically normal adults. Each of the two groups of subjects was additionally tested for one other type of auditory evoked potential, according to the same schedule of eight weekly sessions: middle-latency responses (MLRs: 10 to 50 ms post-stimulus) were collected from Group II (four females and four males), and late responses (50 to 300 ms post-stimulus) from Group I (four females and three males). This paper presents data comparing and contrasting the patterns of relative variability of waveform-peak latency observed in middle-latency, late responses, and the ABR data previously reported. Results document a trimodal distribution of response latency variability, with ABR peak V in one category, characterized by high within-subject stability and low between-subject stability, ABR peaks II, III, and IV, together with MLR peak No in a second category, of intermediate within-subject stability, and a third category consisting of ABR peak I together with all auditory-evoked-potential (AEP) peaks subsequent to MLR peak No, in which consistency of peak latency calculated within subjects approaches the low level of consistency calculated across subjects.

Adult↗

PubMed1990

Individual differences in auditory electric responses: comparisons of between-subject and within-subject variability. V. Amplitude-variability comparisons in early, middle, and late responses.

Each of two groups of adult subjects was tested under a repeated-measures design (Lauter & Loomis, 1986, 1988; Lauter & Karzon, 1990a, b) for ABRs and one other set of responses: middle-latency responses (MLRs: 10 to 50 ms post-stimulus) from Group II (four females and four males), and late responses (50 to 300 ms post-stimulus) from Group I (four females and three males). A companion paper (Lauter & Karzon, 1990b) presents data comparing and contrasting the patterns of relative variability of waveform-peak latency observed in middle-latency, late responses, and the ABR data previously reported. This paper presents amplitude results for the same data sets. Our findings indicate that, as we have reported previously, with regard to between-subject vs. within-subject variability of peak parameters of auditory EP waveforms, normal adult subjects are more consistent when compared with themselves than when compared with each other. This is true at all auditory EP levels tested, from brainstem to cortex, and is observed in both amplitude and latency data, in spite of the fact that the actual values of amplitude-stability measures are an order of magnitude smaller than for latency stability.

Adult↗

PubMed1989

Syllabic pitch perception in 2- to 3-month-old infants.

The pitch patterns present in speech addressed to infants may play an important role in perceptual processing by infants. In this study, the high-amplitude sucking procedure was used to assess discrimination by 2- to 3-month-old infants of rising versus falling pitch patterns in 400-msec synthetic [ra] and [la] tokens. The syllables' intonation contour was modeled on infant-directed speech, and covered a range characteristic of an adult female speaker (180-300 Hz). Group data indicated that the 2- to 3-month-old infants discriminated the pitch contour for both stimuli. Results are discussed with reference to previous studies of syllabic pitch perception.

Arousal↗

PubMed1985

Discrimination of polysyllabic sequences by one- to four-month-old infants.

The goal of this research was to ascertain the effects of suprasegmental parameters (fundamental frequency, amplitude, and duration) on discrimination of polysyllabic sequences by 1- to 4-month-old infants. A high-amplitude sucking procedure, with synthesized female speech, was used. Results indicate that young infants can discriminate the three-syllable sequences [marana] versus [malana] when suprasegmental characteristics typical of infant-directed speech emphasize the middle syllable. However, infants failed to demonstrate discrimination when adult-directed suprasegmentals were used and in several other experimental conditions in which prosodic parameters were manipulated. The pattern of results obtained in the six experiments suggests that the exaggerated suprasegmentals of infant-directed speech may function as a perceptual catalyst, facilitating discrimination by focusing the infant's attention on a distinctive syllable within polysyllabic sequences.

Female↗

PubMed1983

A model for predicting hearing aid performance.

A major problem in selecting a hearing aid is the inability to determine quickly and accurately, from manufacturers' data, the output speech and noise levels over the frequency range of interest and for arbitrary positions of hearing aid controls. This study demonstrates the feasibility of developing a model for a commercial hearing aid and the implementation of the model on a small desktop computer. With the model, output speech and noise levels can be predicted quickly and easily for any combination of control positions, even with the aid driven to saturation. The electroacoustic measurements required for development of the model and the schematic and mathematical models for the aid are presented. The validity of the model is demonstrated by comparing measured values of hearing aid gain, output noise levels, output speech levels and maximum output levels, with corresponding data from the computer model.

Computers↗