Biomedical subjects

C A Champlin

Publications and source records attributed to C A Champlin.

At least 19 recordsLinked to original sources

PubMed2001

Acute effect of nicotine on non-smokers: I. OAEs and ABRs.

This paper is the first in a series of three investigating the role of cholinergic mechanisms in the auditory system by assessing the acute effects of nicotine, an acetylcholinomimetic drug, on aggregate responses within the auditory pathway. In a single-blind procedure, auditory responses were obtained from 20 normal-hearing, non-smokers (10 male) under two conditions (nicotine, placebo). After the drug session, plasma tests revealed a subject's nicotine concentration. The effects of nicotine on early, exogenous responses of the auditory system (otoacoustic emissions and auditory brainstem potentials) are described in this first paper. Results indicated that transdermal administration of nicotine to non-smokers does not significantly affect cochlear activity but does acutely affect the neural transmission of acoustic information. Overall, otoacoustic emissions were unaffected by transdermal nicotine while wave I of the auditory brainstem response was significantly increased in latency and decreased in amplitude.

Administration, Cutaneous↗

PubMed2001

Acute effect of nicotine on non-smokers: II. MLRs and 40-Hz responses.

This paper is the second in a series of three investigating the role of cholinergic mechanisms in the auditory system by assessing the acute effects of nicotine, an acetylcholinomimetic drug, on aggregate responses within the auditory pathway. In a single-blind procedure, auditory responses were obtained from 20 normal-hearing, non-smokers (10 male) under two conditions (nicotine, placebo). The effects of nicotine on central, mesogenous responses of the auditory system (middle latency and 40-Hz responses) are described in this second paper. Results indicated that transdermal administration of nicotine to non-smokers does significantly affect the central, neural transmission of acoustic information. Na-Pa amplitude and Nb latency of the middle latency response and latency measures of the 40-Hz response were acutely altered by the presence of nicotine.

Acoustic Stimulation↗

PubMed2001

Acute effect of nicotine on non-smokers: III. LLRs and EEGs.

This paper is the last in a series of three investigating the role of cholinergic mechanisms in the auditory system by assessing the acute effects of nicotine, an acetylcholinomimetic drug, on aggregate responses within the auditory pathway. In a single-blind procedure, auditory responses were obtained from 20 normal-hearing, non-smokers (10 male) under two conditions (nicotine, placebo). The effects of nicotine on long-latency responses of the auditory system and on electroencephalograms are described in this paper. Results indicated that transdermal administration of nicotine to non-smokers significantly affects the afferent and efferent transmission of acoustic information, as well as enhancing cortical activation. Long-latency response amplitudes and electroencephalogram activity (dominant power and frequencies) were altered by acute doses of transdermal nicotine.

Acoustic Stimulation↗

PubMed2001

Strategies used in feigning hearing loss.

Thirty unsophisticated participants with normal hearing were paid to simulate a hearing loss according to their success in "deceiving" the examiner. The behaviors that these "malingerers" manifested are described. A post-examination interview revealed the strategies used by these participants, which may reflect those strategies used by patients who truly attempt to feign a hearing loss.

Adolescent↗

PubMed2000

Comparison of auditory evoked potentials in heterosexual, homosexual, and bisexual males and females.

The auditory evoked potentials (AEPs) elicited by click stimuli were measured in heterosexual, homosexual, and bisexual males and females having normal hearing sensitivity. Estimates of latency and/or amplitude were extracted for nine peaks having latencies of about 2-240 ms, which are presumed to correspond to populations of neurons located from the auditory nerve through auditory cortex. For five of the 19 measures obtained, the mean latency or amplitude for the 57 homosexual and bisexual females was different from that of the 49 heterosexual females in a manner that implies a masculinization of the auditory systems of the homosexual and bisexual females. A similar masculinization effect was previously observed for the otoacoustic emissions generated by the cochlea. For five other measures, the mean latency or amplitude for the 53 homosexual and bisexual males was different from that of the 50 heterosexual males in a manner that implies a hypermasculinization of the auditory systems of the homosexual and bisexual males. Hypermasculinization has been reported recently for other physical characteristics of homosexual males. One parsimonious interpretation of these findings is that homosexual males and females both were exposed to higher than normal levels of androgens at some point(s) in development. Data are reported only for the female subjects not using oral contraceptives because those drugs can masculinize certain AEP measures.

Bisexuality↗

PubMed2000

Reconsidering the limits of normal hearing.

A proposal is made that 15 dB HL, rather than 25 dB HL, be considered the upper limit of normal hearing sensitivity. This recommendation is based on an explanation of the change from an earlier philosophy and the fact that so many people with hearing levels that average less than 25 dB HL consider themselves to have hearing difficulty. Such reclassification of people with slight to mild hearing losses would dignify their clinical complaints and aid in counseling that would assist them with their hearing difficulties.

Adolescent↗

PubMed2000

The CON-SOT-LOT test for nonorganic hearing loss.

The efficacy of a screening procedure for detecting nonorganic hearing loss using standard audiometric instrumentation was examined. Thirty normal-hearing subjects' responses to continuous and standard and lengthened off-time pulsed tones, using an ascending-descending method, were compared. Subjects were asked to respond to test stimuli in normal-hearing and simulated hearing loss conditions. Data show that there are clinical and statistical differences between subjects' response patterns in the normal-hearing condition as compared to the feigned hearing loss condition. The procedure is offered as a simple method of screening for nonorganic hearing loss.

Adult↗

PubMed2000

The question of phonetic balance in word recognition testing.

Twenty subjects with normal hearing and 15 subjects with mild-to-moderate sensorineural hearing losses were tested with eight lists of words using monosyllabic pronunciation to determine word recognition scores. Four of the lists were taken from Northwestern University Test No. 6 and four were simply made up by randomly selecting words from a dictionary. All of the word lists were used to determine performance-intensity functions. No clinically meaningful differences were observed among the lists.

Adult↗

PubMed1998

Seventh survey of audiometric practices in the United States.

A 5-page questionnaire was sent to 500 audiologists who were randomly selected from the directory of members of the American Academy of Audiology to assess the clinical practices most commonly used by certified audiologists in the United States. Survey content was limited to only those practices and procedures routinely used by audiologists across the nation. The current results were then compared to those obtained in similar studies conducted in 1971, 1972, 1978, 1985, 1989, and 1994 to determine which clinical procedures are being retained, modified, or replaced.

American Speech-Language-Hearing Association↗

PubMed1997

Auditory filters measured at neighboring center frequencies.

Auditory filters were derived in 20 normal-hearing human listeners at center frequencies (CFs) of 913, 1095, 3651, and 4382 Hz using the roex (p,r) method. Comparisons were made between slopes of the filters' skirts at the neighboring CFs with filter output levels of 45 and 70 dB. The same comparisons were made with regard to filter equivalent rectangular bandwidth (ERB). In the 1000-Hz region, the low-frequency slopes (Pl) of filters centered at 913 and 1095 Hz were significantly correlated at both stimulus levels, while the high-frequency slopes (Pu) were similar only at the high test level. In the 4000-Hz region, for sinusoids of 3651 and 4382 Hz, the level effect was clearer as both Pu and Pl values diverged at the low level but were related at high levels. The ERBs centered at the same CFs displayed a similar level dependence. At the stimulus level most likely to be affected by an active feedback mechanism, auditory filters centered at nearly the same frequency displayed quite distinct frequency selectivity, and this trend was stronger in the 4000-Hz region than the 1000-Hz region. The findings suggest that a saturating, active cochlear mechanism may not be distributed evenly, or contribute to peripheral tuning with equal effectiveness throughout the length of the partition.

Adult↗

PubMed1997

Audiologists' professional satisfaction.

This study was primarily designed to explore the job satisfaction of audiologists in the United States. A total of 285 audiologists completed background questions, rated statements, and answered questions about their job satisfaction. Through the use of multiple regression analyses, six statements were identified as being statistically significant in predicting job satisfaction. The most important factor was in the category of challenge.

Adult↗

PubMed1996

Auditory temporal resolution in specifically language-impaired and age-matched children.

Recently there has been renewed interest in the auditory processing capabilities of children with specific language impairment. In this study, eight children with specific language impairment and eight nonimpaired, age-matched peers completed a task to assess temporal resolution abilities. Children were asked to detect a tone in three masking conditions wherein the masker contained silent gaps of 0 msec., 40 msec., or 64 msec. in duration. Thresholds were measured in each masking condition at 500 Hz and 2000 Hz. Across the groups, thresholds decreased (improved) significantly as a function of increases in the duration of the gaps. Children in the two groups exhibited remarkably similar thresholds for the three masking conditions. However, children with specific language impairment required a significantly greater number of ascending trials to achieve the threshold criterion than did age-matched children. Results suggest that language-impaired children perceive temporal aspects of acoustic stimuli as well as their normally developing peers. Attentional mechanisms may play an important role in the difficulties they exhibit in auditory processing.

Attention↗

PubMed1993

Manipulations of the duration and relative onsets of two-tone forward maskers.

The effects of absolute and relative masker duration were investigated using one- and two-tone forward maskers. In the absolute-duration conditions, the duration (D) of a one-component on-frequency (M1; Dm1-alone) or off-frequency (M2; Dm2-alone) masker or the common duration of a two-component masker (Dm1 = Dm2) was varied. Masked threshold increased as duration increased in all three conditions. In the relative-duration conditions, the duration of one masker component was fixed at a relatively long value and the duration of the other component was varied (Dm1 > Dm2 or Dm2 > Dm1). In the Dm1 > Dm2 condition, masked threshold decreased as the duration of Dm2 was increased. In the Dm2 > Dm1 conditions, masked threshold increased and then decreased slightly as the duration of Dm1 was increased. Masked threshold was frequently lower in the M1+M2 than in the M1-alone conditions, indicating psychophysical suppression. Further, masked threshold in the Dm2 > Dm1 condition was always higher than in the corresponding absolute-duration condition (Dm1 = Dm2) having the same M1 duration, indicating masker enhancement. A two-stage neural model was proposed to account for these forward-masking data.

Acoustic Stimulation↗

PubMed1993

Adaptation of suppression as an explanation of enhancement effects.

Delaying the onset of a signal relative to the onset of a simultaneous notched masker often improves the ability of subjects to "hear out" the signal at both threshold and suprathreshold levels. Viemeister and Bacon [J. Acoust. Soc. Am. 71, 1502-1507 (1982)] suggested that such signal-enhancement effects might be attributable to adaptation of the suppression directed from the masker to the signal, thereby releasing the signal from suppression. In support of their hypothesis, Viemeister and Bacon reported that a masker, preceded by an enhancer having no component at the signal frequency, produced more forward masking than did the masker by itself. Here the masker enhancement described by Viemeister and Bacon, signal enhancement, and two-tone suppression were measured in the same six subjects. Parametric manipulations of the masker-enhancement stimulus produced results similar to those previously reported for parallel investigations of signal enhancement, indicating that the two types of enhancement are closely related effects. Although the present data reveal an inverse relationship between the amounts of suppression and enhancement, suggesting that the two processes may be interrelated, no support was obtained for the hypothesis that adaptation of suppression can account for enhancement.

Adaptation, Physiological↗

PubMed1993

Absolute sensitivity measured psychophysically and using auditory steady-state potentials.

Absolute thresholds were measured psychophysically (behaviorally) and physiologically in the same subjects. Psychophysical thresholds were obtained using a modified method of limits. Physiological thresholds were based on auditory steady-state potentials recorded from the scalp. The stimuli for both types of test were click trains, periodic tone bursts and amplitude-modulated tones. The center frequency of the bursts and amplitude-modulated tones was 480 or 2000 Hz. It was found that psychophysical thresholds improved, and physiological thresholds worsened as the stimulus became more frequency-specific. Because of this interaction, the differences between psychophysical and physiological thresholds increased monotonically as a function of frequency specificity. Physiological thresholds obtained with the low-frequency stimuli were lower than those acquired with the high-frequency stimuli, while psychophysical thresholds obtained with the two frequencies were essentially the same.

Acoustic Stimulation↗

PubMed1992

Method for detecting auditory steady-state potentials recorded from humans.

Auditory steady-state potentials were recorded from the scalp of adult humans. The stimuli were 100-microseconds clicks presented at a rate of 39.1/s. Four stimulus levels were used (-20, 0, 10, and 20 dB SL). The presence or absence of a response was determined by three frequency-domain methods and examiners. The frequency-domain methods were: magnitude-squared coherence (MSC), phase coherence (PC), and magnitude only (MO). The MSC method generally had the highest d' values, indicating that it was the most sensitive method for detecting responses. The hearing threshold predicted by the MSC method was the lowest, and it was within 4 dB of the behaviorally measured threshold for the click stimuli. Further, the amplitude of the response was significantly more variable than its phase, and no relation was found between the variability of the amplitude of the response and the amplitude of the noise. In summary, response detection methods that incorporate phase information (such as MSC and PC) should be chosen over methods which incorporate only amplitude information.

Acoustic Stimulation↗

PubMed1990

Acoustic measurements of objective tinnitus.

Ear canal sound pressure levels were measured from a 38-year-old woman who had experienced objective tinnitus in her right ear for approximately 2 years. The tinnitus sounded like a series of "sighs" that were synchronous with her pulse rate. Because the level of the tinnitus fluctuated in a pulsing manner, it appeared to be of vascular origin. Psychoacoustically, the tinnitus behaved like a low-pass masker (cutoff frequency = 1.5 kHz) of about 40 dB SPL. This masking effect was manifested as a low-frequency hearing loss in the subject's right ear. A miniature microphone system was used to monitor the tinnitus before, during, and after a jugular-vein ligation. Because the cause of the tinnitus was only generally known, acoustically monitoring the sound as the jugular vein and/or its tributaries were systematically clamped and then released enabled the site of generation to be known exactly. By monitoring the tinnitus during surgery, the effectiveness of the corrective procedure could be immediately evaluated. Hearing sensitivity in the affected ear returned to normal limits following the elimination of the tinnitus. One year after the surgery, the tinnitus was barely audible to the woman, but only when she positioned her head a specific way. The level of the tinnitus measured in this head-turned condition was markedly lower than the level obtained preoperatively.

Adult↗

PubMed1990

Reductions in overshoot during aspirin use.

The overshoot effect was measured before, during, and after the administration of a moderate dose of aspirin. Prior to the drug, detectability of the 6-ms, 3550-Hz signal was 5-11 dB worse when presented 2 ms after the onset of the 200-ms wideband masking noise than when presented 190 ms after masker onset. Following 4 days of aspirin use, detectability in the long-delay condition was unchanged from the predrug value, but (for four of the five subjects) detectability in the short-delay condition was improved by about 4-8 dB. Thus the overshoot effect was markedly reduced by aspirin because the drug partially counteracted the normally poor detectability for signals presented soon after masker onset. This paradoxical improvement in detectability was accompanied by an aspirin-induced loss in detectability of 5-16 dB for a 200-ms sample of that same signal presented in the quiet. Similar paradoxical effects have previously been obtained by inducing a temporary hearing loss with exposure to intense sound. It is presumed that the same basic mechanisms underlie the parallel outcomes. The so-called cochlear amplifier is discussed in this regard, and also the possibility that the known differences in those primary auditory fibers having high and low spontaneous rates may be involved. A supplementary experiment demonstrated that shifting audibility with either a wideband or a narrow-band background noise does not affect the overshoot effect in the same way as does aspirin or exposure to intense sound, further suggesting that the cochlear amplifier must be altered in order for overshoot to be diminished.

Acoustic Stimulation↗