Biomedical subjects

C A Zizz

Publications and source records attributed to C A Zizz.

4 recordsLinked to original sources

PubMed1996

Postural adjustments produced by moving visual (horizontal optokinetic) patterns.

The effects of horizontal optokinetic stimulation (HOKS) on postural sway were examined in 30 normal subjects aged 20 to 75 years. Fixed-platform posturography was evaluated with the eyes open and closed and during HOKS (20-100 degrees/sec) in the rightward and leftward directions. Forward-backward sway was greater in amplitude than lateral sway under all viewing conditions. Sway amplitude was greater with eyes closed than with eyes open. HOKS significantly enhanced sway amplitude in both directions; however, significant differences occurred only between velocity extremes. Compared to younger subjects, older subjects showed greater forward-backward sway with eyes closed and greater lateral sway during HOKS. HOKS produces a visual cue that conflicts with the other two sensory signals regulating posture (vestibular and proprioceptive systems). Such conflicting visual cues may contribute to serious postural instability and falls in the elderly. The addition of optokinetic stimuli to fixed-platform posturography may enhance its diagnostic value.

Adult↗

PubMed1994

Masking-level difference for spondaic words in 2000-msec bursts of broadband noise.

One protocol developed for the Tonal and Speech Materials for Auditory Perceptual Assessment audio compact disc was the masking-level difference (MLD) for spondaic words in which the words and broadband noise were mixed and recorded at 16 selected signal-to-noise ratios. Four words were recorded at each level. Because it was impossible to monitor the word presentations at negative signal-to-noise ratios, a different paradigm was devised in which the spondaic words were embedded in 2000-msec bursts of noise. Before the materials were finalized for the compact disc, two experiments studied the perceptual characteristics of the paradigm. Experiment I was performed to determine the characteristics of the MLD for spondaic words in 2000-msec bursts of noise at 70 dB SPL. An unexpected finding was that the mean SoNo thresholds were at signal-to-noise ratios 3-4 dB lower than previously reported spondaic word thresholds in continuous broadband noise. Experiment II examined this discrepancy with the spondaic words embedded in continuous noise and in the 2000-msec noise bursts. The results confirmed the 3-4 dB difference between thresholds for the two masker conditions. Based on the pilot data, the spondaic words embedded in 2000-msec bursts of broadband noise at signal-to-noise ratios of 0 dB to -30 dB were recorded on the compact disc in the S pi No paradigm. In the compact disc trials, which involved 120 subjects with normal hearing, the MLDs for the spondaic words recorded on the compact disc were measured on 60 subjects at each of two noise levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗

PubMed1990

Normative data in quiet, broadband noise, and competing message for Northwestern University Auditory Test No. 6 by a female speaker.

Two descriptive experiments were performed on a version of the Northwestern University Auditory Test No. 6 (NU No. 6) recorded by a female speaker that is included on an audio compact disc recently produced by the Department of Veterans Affairs. In Experiment 1, normative psychometric functions for the female speaker version of the NU No. 6 materials were established on 24 young adults for three monaural listening conditions (in quiet, in 60-dB SPL broadband noise, and in 60-dB SPL competing message). The 60-dB SPL broadband noise shifted the psychometric function for the NU No. 6 words 33 dB, whereas the 60-dB SPL competing message shifted the function only 18-22 dB. In contrast to the slopes of the quiet and noise conditions (4.5%/dB), the slope of the competing message function was more gradual (3.5%/dB). In Experiment 2, comparisons between the psychometric functions for the female and the original male speaker versions of NU No. 6 in quiet and in broadband noise were made on 8 young adults. In comparison to the psychometric functions for the male speaker version of NU No. 6, the functions for the female speaker version of NU No. 6 were displaced between the 10-90% correct points to higher sound-pressure levels by 10-13 dB in quiet and by 12-16 dB in noise. The difference in performance on the two versions of NU No. 6 is attributed to spectral differences between the two sets of materials that produced a calibration anomaly.

Adult↗

PubMed1988

Reliability of spontaneous otoacoustic emission suppression tuning curve measures.

The purpose of this investigation was to study the reliability of spontaneous otoacoustic emission (SOAE) suppression tuning curve (STC) measurements. Two repetitions of an SOAE STC, using a 4-dB suppression criterion, were obtained from 5 subjects who exhibited stable SOAE level (SD less than or equal to 1.5 dB) and SOAE frequency (+/- 5 Hz). Analyses of variance revealed no significant difference between the SOAE STC trials (p greater than .05). The SOAE frequency was below the SOAE STC tip, which is similar to the relationship between the probe frequency and a simultaneously masked psychophysical tuning curve. The mean slope of the SOAE STC low-frequency segment was 53.7 dB/octave, whereas the mean slope of the SOAE STC high-frequency segment was 124.8 dB/octave. The mean low- to high-frequency slope ratio was 2.4. The mean Q10 value for the 5 subjects was 5.3. The SOAE STC low- and high-frequency slopes and Q10 were similar to psychophysical tuning curve data obtained in simultaneous masking and physiological tuning curve data.

Adult↗