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Biomedical subjects

A J Klein

Publications and source records attributed to A J Klein.

34 records · Page 2Linked to original sources
PubMed1986

Masking effects on ABR waves I and V in infants and adults.

The effects of high- and low-pass masking on waves I and V of the auditory brain stem response (ABR) were measured in normal infants who were 2-4 weeks old, and in adults. The signal was a 4-kHz tone pip presented at 86 dB peak equivalent sound-pressure level (p.e.SPL). The masking patterns were different for latency and amplitude criteria, and were also different for infants and adults. The largest difference between infants and adults was seen in the wave I data. Low-pass maskers were very disruptive of the infant wave I, while little or no effect was noted on the adult wave I. High-pass maskers were very disruptive of the adult wave I, while less of an effect was measured on the infant wave I. The wave V data were similar between groups. Cochlear regions which contribute most importantly to wave I extend up to one octave above the frequency of the signal in adults, and to one-half octave above the signal frequency in infants. The reasons for the differences found between infants and adults are uncertain. Two possible mechanisms which can explain these data are differences in peripheral auditory sensitivity, and differences in tuning characteristics of the auditory system.

Adult↗
PubMed1984

Frequency and age-dependent auditory evoked potential thresholds in infants.

Auditory evoked-potential thresholds to 0.5, 4.0 and 10.0 kHz tone pips were measured in 40 normal infants 2-28 wks old and 14 normal hearing adults. Thresholds to 500 Hz tone pips were based upon the steady-state, 40 Hz evoked potential. Thresholds to 4.0 and 10.0 kHz tone pips were based upon the brainstem response. Stimulus intensity was varied in 5-dB steps for threshold search. The greatest difference between infant and adult thresholds occurred at 4.0 kHz. The magnitude of this difference decreased with age; however, differences were still significant up to 28 wks of age. No significant differences were seen at 500 Hz. To the 10.0 kHz stimulus only the youngest (2-4 wk) infants had thresholds that were significantly higher than adults. The reasons proposed to explain these results are complex interactions between immaturity of the conductive mechanism, brainstem pathways, and possibly the cochlea.

Acoustic Stimulation↗
PubMed1983

Properties of the brain-stem response slow-wave component.

A slow-wave component of the brain-stem response recordable to signals at low sensation levels shows some promise for estimating hearing thresholds at low frequencies. This study describes several properties of this slow-wave response (SWR) in 30 normal hearing subjects and examines correlations with psychophysical thresholds. Acoustic signals were tone pips at 0.25, 0.5, 1, 2, and 4 kHz with 3-ms rise-fall times and no plateau. Repetition rate was 40/s. The EEG was filtered at 20 to 1,500 Hz before averaging. Results showed SWR thresholds were on the average about 15 dB higher than behavioral thresholds, however, the range was 0- to 35-dB sensation level. A large decrease in SWR amplitude and a 20-dB increase in threshold could occur in states of deep sleep. The SWR appears to be useful for estimating low-frequency thresholds, but the 35-dB threshold range in normal hearing subjects should be considered when interpreting some SWR results.

Acoustic Stimulation↗
PubMed1983

Properties of the brain-stem response slow-wave component. II. Frequency specificity.

Frequency specificity of a slow-wave response (SWR) of the brain-stem response (BSR) was measured with a simultaneous masking tuning-curve paradigm. The SWR tuning curves to 250-Hzz tone pips show greatest sensitivity to 350- to 400-Hz maskers. The SWR tuning curves to 500-Hz tone pips are most sensitive to 500- and 600-Hz maskers. Higher-frequency tuning curves show greatest sensitivity when masker frequency is equal to signal frequency. Frequency specificity is preserved to 80-dB sound-pressure level or 55- to 65-dB sensation level. Tone-pip frequencies of 0.5, 1.0, 2.0 and 4.0 kHz appear to be adequate stimuli for eliciting a frequency-specific SWR. The 250-Hzz tone pip does not elicit a frequency-specific SWR and is probably not a useful test frequency under the present recording conditions.

Acoustics↗
PubMed1982

An analysis of auditory brainstem responses in infants.

Acoustic brainstem responses (ABRs) were recorded from 148 infants from 4 to 60 weeks of age. 28 subjects returned to the laboratory 3 or more times for additional recordings. Filtered clicks of 1, 2, 4 and 8 kHz were presented at two intensities, 30 and 50 dB HL re the average threshold for a group of young adults. Responses to a broadband click, 50 dB nHL, were also recorded. The latencies of waves I, III and V were measured. Wave I latencies for the 8 kHz filtered click showed no change but those for lower frequencies decreased with age. The latency decreases with age were largest for wave V, and, among the filtered clicks, was largest for the responses to 1 kHz. Best-fitting curves were determined for latency vs. age for each filtered click and for the broadband click. Wave V--Wave I latency differences showed that the rostral conduction time for responses to the 8 kHz FC decreased with age and, for the 1 kHz filtered click (50 dB), remained constant. The early development of basal regions in the cochlea is viewed as insuring the delivery of a wide range of frequencies to rostral segments of the auditory system. The limiting feature of maturation is at rostral sites. The immature auditory system appears to be fully capable of transducing low frequency stimuli, but not high frequencies.

Acoustic Stimulation↗
PubMed1981

Physiological (waves I and V) and psychophysical tuning curves in human subjects.

Tuning curves obtained on wave I (VIII nerve) and wave V of the auditory brainstem response were recorded simultaneously with ear-canal and forehead electrodes. On these same human subjects using the same acoustic stimuli psychophysical tuning curves were also measured. For each subject the three tuning curves were qualitatively similar; however, both intra- and inter-subject quantitative differences were present. The best agreement was between the psychological and the wave V tuning curves. The wave I tuning curve differed from the other two mainly on the high-frequency side by showing a wider response area. The main difference between both physiological tuning curves and the psychophysical tuning curve occurred near center frequency of the probe signal: Physiological tuning curves had deeper tips in comparison to the psychophysical tuning curves which had shallow rounded tips. This might be due to energy splatter of the short-duration signal which can significantly effect psychophysical judgments while minimally contributing to the physiological responses. A precise measure of sharpness of tuning was difficult to obtain; however, the response area of wave I appears to be more biased towards high-frequency cochlear neurons than either wave V or psychophysical judgments. Tuning curves are shown to be a viable method of relating physiological to psychophysical measurements in human subjects.

Action Potentials↗
PubMed1981

Physiological and psychophysical measures from humans with temporary threshold shift.

Tuning curves and amplitude-intensity functions on wave I and wave V of the auditory-evoked brain stem response and psychophysical tuning curves were obtained from human subjects (N = 5) with noise-induced temporary threshold shift (TTS). All tuning curves were measured with the same stimuli. Maskers were pure tones presented simultaneously with the signal which was a 3.6-kHz tone pip. TTS was produced by a narrow-band noise centered at 2.6 kHz and presented at 86 dB SPL for 8 h. The maximum mean TTS was 28 dB and occurred at 3.5 kHz. Although intersubject variability of TTS was small, individual differences in other measurements were substantial. In some subjects, amplitudes of waves I and V decreased following the noise exposure with wave I typically being more affected, while in other subjects, little or no change in amplitude occurred. All tuning curves had wider response areas following noise exposure. In a given subject, changes in psychophysical and wave V tuning curves were similar and were less than changes measured for wave I. Recovery of tuning curves (low- and high-frequency side) to pre-exposure values required between 7 and 41 h depending upon the individual and preceded complete recovery of TTS.

Adult↗
PubMed1979

A technique for separating endogenous from exogenous human cortical potentials.

In a temporal discrimination paradigm, if signal duration is the stimulus dimension to be discriminated, the moment of subject's decision can be manipulated by varying the duration of the target stimulus. As stimulus duration is lengthened, task-contingent potentials related to the decision process can be separated from those evoked by stimulus onset. Analysis of individual evoked responses indicates that 3 task-contingent components, occurring at 220, 300 and 340 msec are precisely time-locked to the moment of decision.

Acoustic Stimulation↗
PubMed1978

Acoustically dependent latency shifts of BSER (wave V) in man.

The latencies of wave V in Brain Stem Evoked Responses (BSER) elicited by a set of acoustic transients were measured. The stimuli were produced by delivering pulses to two filters, arranged in series. The filters were set so that the maximum acoustic energy in the transients, i.e., filtered clicks, occurred at 0.5, 1, 2, 4, or 8 kHz. The filtered clicks were presented via earphones at a rate of 30/s at 20, 40, or 60 dB HL to ten subjects with normal hearing. The latencies of wave V varied systematically with center frequency of the filtered clicks when they were each at the same HL. Stimuli presented at 40 dB HL produced the greatest opportunity for relating stimulus frequency to latency. The latencies for a smaller set of responses to stimuli presented at 10/s were the same as those for the principal data taken at 30/s. The changes in latency of wave V due to frequency are similar to those observed by other investigators in whole-nerve responses recorded in man.

Acoustic Stimulation↗
PubMed1978

Payments arrangements.

No matter what financial arrangements are made with patients, there is no foolproof method of ensuring payment. As stated earlier, the financial arrangement does not indicate mistrust of the patient, but is a means of communication. If we accept the fact that nearly all patients have full intentions of meeting their financial obligations, the guiding rule should be flexibility. Inflexibility when making financial arrangements may limit the growth of your practice. Sensitivity is an important ingredient in helping to understand and to meet your patient's needs. Many more patients will accept necessary dentistry if they are given the opportunity to select a method of payment with which they are comfortable.

Dental Offices↗
PubMedDate not supplied

Thresholds of filtered transients.

Absolute and masked thresholds were obtained for sinusoids, one-third-octave filtered noise, one-third-octave filtered clicks, and for broadband noise and clicks as a function of repetition rate of the filtered clicks. The results indicate that if signal energy is computed for each stimulus, then similar absolute and masked thresholds can be obtained. Thresholds for repetition rate and number of clicks were similar to published results on temporal integration of tones. These results provide a direct and objective means for measuring the level of brief narrow-band stimuli and support the use of these signals as a means of probing auditory sensitivity.

Acoustic Stimulation↗