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PubMed1989

Taste thresholds in man are differentially influenced by hydrocortisone and dexamethasone.

The present study focused on sensory processing (taste threshold) in healthy young men given different cortisol doses within the normal physiological range. It aimed to differentiate the effects of dexamethasone, a synthetic pure glucocorticoid, compared to hydrocortisone, which has both glucocorticoid and mineralocorticoid properties. In a double-blind, cross-over design, 18 male subjects participated in three sessions. Subjects were pretreated orally with hydrocortisone (50 mg), dexamethasone (2 mg) or placebo. Taste detection was tested by a forced-choice three stimulus drop technique to determine detection acuity and a signal detection procedure to determine the ability to detect differences in NaCl concentration. Cortisol concentrations were determined in blood and saliva. Hydrocortisone and dexamethasone had opposite effects on taste detection acuity. With the highest cortisol levels after intake of hydrocortisone, subjects made more errors in detection trials with respect to stimuli close to the absolute taste detection threshold than after intake of dexamethasone. Detection of differences was impaired by both glucocorticoids. This type of behavioral study in man may help clarify the roles of heterogeneous corticosteroid receptor systems within the human brain.

Adolescent↗
PubMed1983

Meridional variations in the line orientation discrimination of the cat.

Cat's differential orientation thresholds were measured with single lines presented in succession. Differential orientation thresholds measured at horizontal or vertical orientations were smaller (median 2.9 degrees) than those measured at oblique orientation (median 4.7 degrees). Replications of the experiments showed that the oblique effect was stable over a period of 2 years. Using the same behavioral methods grating acuity was measured and did not show an oblique effect. These behavioral observations are compared with the physiological data on orientation specificity of area 17 cells. This comparison suggests that the most likely explanation of the meridional variation in orientation discrimination is the meridional variation in orientation preference of area 17 S cells.

Animals↗
PubMed1992

Automatic perimetry in detecting early glaucomatous visual field defects. A follow-up study.

A prospective study was conducted to identify the value of the differential light threshold changes in glaucoma patients. Using Humphrey Field Analyzer, we determined the differential light threshold on 42 preselected points in the Bjerrum area in the age-matched early glaucoma and normal group, each in 50 eyes, whose initial Goldmann perimetries were normal. It was found that both generalized and localized sensitivity of the retina declined obviously in the glaucomatous group. After Goldmann perimetry follow-up for 2.5 years, 24 eyes showed reproducible typical visual field defects (VFD) in the glaucoma group, which appeared in the same location where light threshold had reduced previously. Therefore, a typical glaucoma VFD was preceded by the slight localized depression of light sensitivity in the Bjerrum area.

Adult↗
PubMed1989

Pressure pain thresholds, clinical assessment, and differential diagnosis: reliability and validity in patients with myogenic pain.

Four studies are presented testing the validity and reliability of pressure pain thresholds (PPTs) and of examination parameters believed to be important in the clinical assessment of sites commonly used for such measures in patient samples. Forty-five patients with a myogenous temporomandibular disorder were examined clinically prior to PPT measures. Criteria for history and examination included functional aspects of the pain, tissue quality of the pain site, and the type of pain elicited from palpation. Control sites within the same muscle and in the contralateral muscle were also examined. PPTs were measured as an index of tenderness using a strain gauge algometer at these sites. The data from the 5 male subjects were excluded from subsequent analyses due to the higher PPT in the males and to their unequal distribution among the various factorial conditions. The first study demonstrated strong validity in PPT measures between patients (using pain sites replicating the patients' pain) and matched controls (n = 11). The PPT was not significantly different between the primary pain site (referred pain and non-referred pain collapsed) and the no-pain control site in the same muscle (n = 16). The PPT was significantly lower at the pain site compared to the no-pain control site in the contralateral muscle (n = 13). The second study indicated adequate reliability in patient samples of the PPT measures. In the third study, the PPT was significantly lower at sites producing referred pain on palpation compared to sites producing localized pain on palpation. The PPT findings from the control sites were inconsistent on this factor. The fourth study presented preliminary evidence that palpable bands and nodular areas in muscle were most commonly associated with muscle regions that produce pain; such muscle findings were not specific, however, for regions that produce pain. Further, the intraexaminer reliability in reassessing these pain sites qualitatively was only fair. Referred pain had a poor association with the pain pattern and physical findings, which may suggest a need to reevaluate part of the theory regarding referred muscle pain. The reliability of PPT measures was better overall than the reliability of the signs and site-specific symptoms, suggesting that pressure pain thresholds may be an important tool in clinical studies of pain. PPT measures demonstrate a high within-subject variability in pain patient subjects as well as non-pain subjects.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed2006

Near-threshold production of phi mesons in pp collisions.

The pp-->ppphi reaction has been studied at the Cooler Synchrotron COSY-Jülich, using the internal beam and ANKE facility. Total cross sections have been determined at three excess energies epsilon near the production threshold. The differential cross section closest to threshold at epsilon=18.5 MeV exhibits a clear S wave dominance as well as a noticeable effect due to the proton-proton final-state interaction. Taken together with data for ppomega production, a significant enhancement of the phi/omega ratio of a factor 8 is found compared to predictions based on the Okubo-Zweig-Iizuka rule.

Journal Article↗
PubMed2005

Nonlinear explanation for bone-conducted ultrasonic hearing.

Human listeners can perceive speech from a voice-modulated ultrasonic carrier presented via a bone-conduction stimulator. This study explored the psychoacoustic characteristics and underlying mechanisms of ultrasonic hearing by measuring difference limens for frequency (DLF) for pure tones modulated onto ultrasonic carriers. Human subjects were presented with two pulsed tones and asked to judge whether the first or the second had the higher pitch. When amplitude modulation was based on a double side-band transmitted carrier, the DLFs were as small as those from the air-conducted pure tones at 0.25-4 kHz. Ultrasounds yielded larger DLFs for tones with low (0.125 kHz) and high (6-8 kHz) frequencies. Results were essentially identical between the two types of carriers, sine wave (30 kHz) and bandpass noise (30+/-4 kHz), despite the different bandwidths in the ultrasonic range. When amplitude modulation was based on a double side-band suppressed carrier, DLFs corresponded to those from tones with double frequencies. These results suggest nonlinear conduction that demodulates audible signals from ultrasounds and provides inputs to the cochlea.

Acoustic Stimulation↗
PubMed2000

Increased noise severity limits potentiation of noise induced hearing loss by carbon monoxide.

This study evaluates the influence of noise intensity and duration on auditory dysfunction due to simultaneous exposure to noise and carbon monoxide (CO). Previous studies have demonstrated that CO potentiates noise induced hearing loss (NIHL). It is not known whether auditory dysfunction due to combined exposure parallels impairment due to noise alone. Based on the 5 dB exchange rate between noise intensity and exposure doubling time, equivalent noise exposure conditions were used. Long Evans hooded rats were divided into groups that received noise alone (95, 100 and 105 dB SPL), and noise plus CO (1200 ppm), for durations of 4, 2 and 1 h, respectively. Controls were exposed to air or CO alone. Thresholds were evaluated 4 weeks later using an electrophysiological endpoint, the compound action potential threshold. Results demonstrate that the 5 dB exchange rate is not conserved under the conditions and subjects used. Moreover, dysfunction due to combined exposure did not parallel dysfunction due to noise alone. Further, although an increase in exposure duration results in increased auditory dysfunction, no further potentiation of NIHL by CO is observed. This suggests that at increasing noise severity, dysfunction due to combined exposure is limited by impairment due to noise alone.

Acoustic Stimulation↗
PubMed2001

Cochlear implant thresholds: comparison of middle latency responses with psychophysical and cortical-spike-activity thresholds.

The electrically evoked middle latency response (EMLR) is a potentially useful measure of activation of the auditory system by a cochlear prosthesis. The present study compared cochlear prosthesis thresholds determined using EMLR with thresholds determined for psychophysical detection and for spike activity in cortical neurons. In systemically deafened guinea pigs, the difference between EMLR and psychophysical threshold level varied, with differences ranging from -4.6 dB (EMLR threshold more sensitive) to +10.7 dB (psychophysical threshold more sensitive) across animals and phase durations. Threshold differences between EMLR and auditory cortex neural spike responses were similar in magnitude and range (-6 to +15 dB) to those seen for EMLR vs. psychophysical thresholds. These ranges are comparable to the behavioral operating range for a given condition. In 3 of 12 subjects, the EMLR was absent for some or all electrode configurations tested, even at levels well above the threshold for psychophysical detection or cortical neuronal response. These results suggest that neither the EMLR thresholds nor cortical neuronal spike thresholds are an adequate substitute for psychophysical measures of threshold. While not sufficient for use in place of psychophysical measures, EMLR threshold level is strongly correlated with psychophysical threshold level across subjects (R(2)=0.82). Interestingly, plots of thresholds vs. phase duration were roughly parallel for psychophysical and EMLR thresholds, in contrast to the divergence of psychophysical and more peripheral (e.g., electrically evoked auditory brainstem response) evoked neural threshold vs. phase duration functions.

Action Potentials↗
PubMed1989

Effects of click rate and electrode orientation on threshold of the auditory brainstem response.

This study evaluated the effects of stimulus presentation rate and electrode orientation on ABR threshold. Six normal-hearing adults served as subjects. ABRs were recorded from three orthogonal electrode pairs in response to click stimuli at rates of 48 and 21/s. Psychophysical thresholds were determined for each of these stimuli, and ABRs were recorded with stimuli between 0 and 10 dB SL in 2-dB steps. A ratio of ABR signal strength to noise variance (Fsp) was the criterion used to define threshold. Specifically, an Fsp value of 2.25, equivalent to a 95% response confidence using 5 and 250 degrees of freedom, was the criterion used to determine response presence within a maximum of 10,000 sweeps per average. Results revealed that, for normal-hearing adult subjects, click rate up to 48/s does not influence the sensation level at which a detectable response can be found, and a nearly vertical electrode orientation is optimal for recording the response at low levels. The predicted difference between psychophysical and ABR thresholds with a vertical electrode orientation, using 10,000 sweeps per average, up to 48 clicks per second, and an Fsp criterion of 2.25 is 4.4 dB.

Auditory Threshold↗
PubMed2003

A comparison of psychophysical procedures for level-discrimination thresholds.

Five different psychophysical procedures were used to measure level-discrimination (also called intensity discrimination) thresholds for 1-kHz tones at two levels (30 and 90 dB SPL) and two durations (10 and 500 ms). The procedures were the classic transformed up-down staircase method with a two-alternative forced-choice (2AFC) paradigm (UPD), 15- and 50-trial implementations of the method of maximum likelihood (MML) with a cued yes-no paradigm, and 18-trial implementations of ZEST using both cued yes-no and 2AFC paradigms. Results obtained from nine normal listeners show that estimates of level-discrimination thresholds for the four conditions are similar across all five procedures when different points of convergence are accounted for. The variance of threshold estimates within listener and condition was smallest for UPD, largest for the MML with 15 trials, and statistically indistinguishable among the others. The sweat factors ranged from 5.5 for MML with 50 trials to about 1.4 for UPD and ZEST. Simulations show that ideal performance of procedures may be far from real-life experience and that these deviations are likely to depend on complex interactions between listener behavior and parameter choices used for implementing the procedures. Therefore, empirical verification is important for judging the effectiveness of psychophysical procedures.

Adolescent↗
PubMed2006

Opinions on cochlear implant use in senior MED-EL patients.

This study assessed the subjective benefits of cochlear implants in senior patients wearing a MED-EL device. Data was compared with previous studies to assess the influence of recent speech-coding strategies and behind-the-ear speech processors; users of the behind-the-ear device and the body-worn device were also compared. An adaptation of the Nucleus 22-channel survey was sent to 141 cochlear implant users. The survey assesses perception of the device, communication benefits, handling the device and quality of life. Ninety-five surveys were returned. Results demonstrate that advanced technology provides greater benefit now than 9-13 years ago, notably: improved listening across noise, better understanding on the telephone and better speech perception. Users of the behind-the-ear device did not report more difficulties than body-worn device users but demonstrated better performance. Results show a positive outcome for cochlear implantation in a MED-EL seniors group.

Age Factors↗
PubMed1994

Stapedius reflex and EABR thresholds in experienced users of the Nucleus cochlear implant.

Evoked auditory brainstem responses (EABR) and stapedius reflex thresholds were established in 7 experienced users of the Nucleus cochlear implant. Even using biphasic 400 microseconds/phase clicks for the EABR, responses were observed in only 5 patients; no stapedius reflex (SR) was seen in 3 patients, 2 of whom had a history of middle-ear disorder. The EABR threshold varied widely between subjective threshold and uncomfortable loudness level (ULL) for the same stimulus. The average SR threshold was found somewhat more consistently at 66% of the dynamic range between threshold and ULL, but grossly overestimated the most comfortable level (MCL) in most cases. To obtain equal loudness at the same current level we suggest that broad clicks (300 microseconds/phase) be used for EABR measurements, thus compensating for the lower repetition rate of EABR stimulus compared with the device fitting stimulus.

Acoustic Stimulation↗
PubMed1984

Reliability of auditory function tests in severely hearing-impaired and deaf subjects.

The test-retest variability of a series of auditory functions has been investigated in a group of severely hearing-impaired and deaf subjects (64 ears, median Fletcher index: 80 dB) and in a group of 10 controls with normal hearing. An adaptive forced-choice procedure was used for both groups. The functions were: tone audiogram, difference limen for intensity, difference limen for frequency, modulation transfer function and critical ratio. In spite of sometimes strongly deviating function values within the hearing-impaired group, the test-retest variability of the two groups was found to be of the same order of magnitude, except for the tone audiogram where the variability in the hearing-impaired group was twice that for the control group.

Adolescent↗
PubMed1985

Investigations of the residual hearing capacity of severely hearing-impaired and profoundly deaf subjects.

Speech reception functions (maximum discrimination score for phonemes, speech reception threshold) and auditory functions (pure-tone audiogram, difference limens for frequency and intensity, temporal modulation transfer function, critical ratio and temporal integration) have been investigated in a group of severely hearing-impaired and deaf subjects (median Fletcher index: 80 dB), for different frequency regions (250, 1 000 and 2 000/4 000 Hz). The correlations between the different functions were calculated on the basis of characteristic numbers, derived from the originally measured functions, in the indicated frequency regions. The residual hearing capacities could be described best with two factors, one reflecting the distortion term in the speech reception threshold and the other representing the frequency discrimination for high-frequency tones. It was found that residual hearing capacities are present, at least up to a Fletcher index of 105 dB.

Adolescent↗
PubMed1990

Frequency specificity of the auditory brainstem response elicited by 1,000-Hz filtered clicks.

In normal-hearing subjects and in subjects with a flat cochlear hearing loss, auditory brainstem responses (ABR) were recorded at various levels of a 1,000-Hz filtered click stimulus with and without high-pass filtered masking noise. The difference in latency of the major peak in the ABR for the masked and unmasked condition was zero at the ABR threshold. We regard this as proof of the frequency specificity of the 1,000-Hz filtered click-stimulated ABR threshold. The difference between ABR threshold and the subjective puretone threshold at 1,000 Hz amounted to 19 dB in normal-hearing subjects and to 10 dB in subjects with a flat cochlear hearing loss. This is probably related to loss of temporal integration and an abnormal loudness growth (recruitment).

Acoustic Stimulation↗