Search PubMed⌕ Search

Biomedical subjects

C W Turner

Publications and source records attributed to C W Turner.

At least 91 records · Page 5Linked to original sources
PubMed1987

Effects of noise and hearing loss upon frequency discrimination.

Frequency discrimination in quiet and in the presence of several levels of low-frequency masking noise was measured at 500, 1,000 and 2,000 Hz in both normal-hearing and hearing-impaired subjects. The test signals were presented at 80 dB SPL; all test signals were at least 10 dB above each subject's masked threshold. As a group, the hearing impaired subjects had larger frequency difference limens than the normal subjects, especially in frequency regions of greatest sensitivity loss. The masking noise produced a similar increase in frequency difference limens in both groups. Although several previous speech recognition studies have demonstrated an interactive effect between the presence of hearing loss and masking noise, the results of the present study demonstrate that frequency discrimination performance for normal-hearing and hearing-impaired subjects is not differentially affected by the addition of masking noise.

Hearing Loss↗
PubMed1987

Auditory filtering and the discrimination of spectral shapes by normal and hearing-impaired subjects.

A review of the literature suggests that many hearing-impaired patients suffer from sensory deficits in addition to the reduced audibility of speech signals. Poor frequency resolution, or abnormal spread of masking, is a consistently identified deficit in sensorineural hearing loss. Frequency resolution was measured in individual subjects using the input filter pattern paradigm, and the minimum detectable amplitude of a second-formant spectral peak in a spectral-shape discrimination task was also determined for each subject. The two tasks were designed to test the identical frequency regions in each subject. A nearly perfect correlation was found between the degree of frequency resolution as measured by the input filter pattern and performance on the spectral-shape discrimination task. These results suggest that measures of frequency selectivity may offer predictive value as to the degree of impairment that individual hearing-impaired patients may have in perceiving the spectral characteristics of speech, and also lead to suggestions for signal processing strategies to aid these patients.

Auditory Threshold↗
PubMed1986

Spread of masking in normal subjects and in subjects with high-frequency hearing loss.

Upward spread of masking and remote masking were investigated in 4 subjects with closely matched high-frequency hearing losses. Masked thresholds in the presence of a high-frequency or a low-frequency bandpass noise were obtained using an adaptive-threshold procedure. 'Abnormal' upward spread of masking existed for the impaired subjects at some test frequencies when compared to the masking predicted on the basis of normal masking results and hearing-impaired quiet thresholds. Remote masking thresholds were usually shifted to the same absolute levels for normal and hearing-impaired subjects. These results demonstrate that speech reception in noise for listeners with high-frequency hearing loss could be affected by spread of masking and levels of hearing loss.

Acoustic Stimulation↗
PubMed1985

Level effects in complex stimulus discrimination.

The dependence of spectral-shape discriminations upon presentation level was studied using stimuli consisting of a bandpass noise and a less intense pure tone. The level of the noise band was held constant (+10 dB) relative to the level of the tone, and the minimum change in the intensity of the tone was measured across a range of presentation levels. The results demonstrated that, for tonal frequencies located near the upper edge of the noise band, subject's optimal performance occurred at intermediate presentation levels and became considerably poorer at high levels. This result is in accordance with upward spread of masking and emphasizes that presentation level is an important parameter to consider when measuring discriminations of complex spectral shapes.

Acoustics↗
PubMed1984

Interpersonal aggression and the type A coronary-prone behavior pattern: a theoretical distinction and practical implications.

Past research suggests that Type As are more aggressive than Type Bs. However, little is known about the nature of that aggression. The present two studies investigated the theoretical distinction between hostile aggression and instrumental aggression and examined the practical implications of this distinction. Study 1 used a modified version of the Buss teacher-learner procedure that allowed the isolation of hostile from instrumental acts. Results indicated that a prior task frustration produced greater aggression by Type As than Type Bs but only under conditions where the aggressive act could not affect a confederate's immediate performance (i.e., hostile aggression). Study 2 examined the representation of Type As and Type Bs among perpetrators of intrafamily violence. Results indicated that Type As were more likely than Type Bs to exhibit the extreme hostility found in child abuse. Both studies suggest that a lack of control may underlie the greater aggression displayed by Type As than Type Bs.

Adult↗
PubMed1984

Sensorineural hearing loss and the discrimination of vowel-like stimuli.

It has been hypothesized that the wider-than-normal auditory bandwidths attributed to sensorineural hearing loss lead to a reduced ability to discriminate spectral characteristics in speech signals. In order to investigate this possibility, the minimum detectable depth of a spectral "notch" between the second (F2) and third (F3) formants of a synthetic vowel-like stimulus was determined for normal and hearing-impaired subjects. The minimum detectable notch for all subjects was surprisingly small; values obtained were much smaller than those found in actual vowels. An analysis of the stimuli based upon intensity discrimination within a single critical band predicted only small differences in performance on this task for rather large differences in the size of the auditory bandwidth. These results suggest that impairments of auditory frequency resolution in sensorineural hearing loss may not be critical in the perception of steady-state vowels.

Hearing Loss, Sensorineural↗
PubMed1984

Speech recognition in a special case of low-frequency hearing loss.

Recognition of speech stimuli consisting of monosyllabic words, sentences, and nonsense syllables was tested in normal subjects and in a subject with a low-frequency sensorineural hearing loss characterized by an absence of functioning sensory units in the apical region of the cochlea, as determined in a previous experiment [C. W. Turner, E. M. Burns, and D. A. Nelson, J. Acoust. Soc. Am. 73, 966-975 (1983)]. Performance of all subjects was close to 100% correct for all stimuli presented unfiltered at a moderate intensity level. When stimuli were low-pass filtered, performance of the hearing-impaired subject fell below that of the normals, but was still considerably above chance. A further diminution in the impaired subject's recognition of nonsense syllables resulted from the addition of a high-pass masking noise, indicating that his performance in the filtered quiet condition was attributable in large part to the contribution of sensory units in basal and midcochlear regions. Normals' performance was also somewhat decreased by the masker, suggesting that they also may have been extracting some low-frequency speech cues from responses of sensory units located in the base of the cochlea.

Adult↗
PubMed1983

Type A and type B attentional responses to aesthetic stimuli: effects on mood and performance.

Recent investigations of the Type A coronary-prone behavior pattern have found that Type A's focus their attention on a central task and actively inhibit attention to peripheral distracting stimuli. This attentional difference has resulted in greater performance for Type A's than for Type B's. However, research on aesthetic stimuli suggests that the focused attention of Type A's may not always be adaptive for solving frustrating cognitive tasks, particularly when paying attention to a peripheral stimulus could enhance performance by reducing negative emotions. Simple, predictable, aesthetic stimuli can have a soothing effect, which reduces negative emotions and enhances performance. The present study found that Type B's had improved affect and performance from attending to a soothing peripheral stimulus (simplex melodies) while working on a frustrating cognitive task. Neither the performance nor the affect of Type A's was influenced by the simplex music, because they apparently suppressed paying attention to these melodies.

Achievement↗
PubMed1982

Kanamycin and bumetanide ototoxicity: anatomical, physiological and behavioral correlates.

Severe hair-cell degeneration and cochlear dysfunction was observed in chinchillas examined at 60 days (or longer) after administration of a single injection of 150 mg/kg kanamycin, followed 2 h later by a single injection of 20 mg/kg bumetanide. Outer hair cells in the cochlear base were most severely affected. While inner and outer hair-cell loss was common, some animals showed large regions along the basilar membrane where almost all inner hair cells were present and almost all outer hair cells were absent. Wherever areas of complete degeneration of the organ of Corti occurred, a small, diffuse population of nerve fibers within the spiral lamina was always present. Single-unit tuning curves correlated best with anatomical observations, compared with the other functional measures of auditory sensitivity that were obtained (behavioral audiogram and compound action potential thresholds). Results indicated that behavioral detection of auditory stimuli is relatively independent of innervation density as long as a few inner hair cells are present. Thus, the cross-fiber threshold envelope of the single-unit tuning curves appeared very similar to the behavioral audiogram.

Animals↗
PubMed1982

Frequency discrimination in regions of normal and impaired sensitivity.

Psychometric functions for frequency discrimination were obtained from both normal-hearing and hearing-impaired listeners at 300, 1200, and 3000 Hz. Difference limens for frequency (DLFs) were derived from those psychometric functions after repeated practice sessions, ensuring that all listener's results represented levels of optimum performance. Practice effects were found to be considerable in many listeners. The psychometric functions for all listeners, both normal-hearing and hearing-impaired, were well described by linear functions of performance level (d') and frequency difference (Hz), which passed through the zero origin. Those listeners with normal sensitivity thresholds at all frequencies exhibited the most acute frequency discriminations. Listeners with sensitivity losses at high frequencies exhibited larger DLFs, even at lower test frequencies where sensitivity thresholds were normal.

Adult↗
PubMed1980

The effect of thyroid dysfunction on the chronotropic response to noradrenaline.

Dose-response curves to noradrenaline in the presence and absence of beta-receptor antagonists were established with isolated atria from euthyroid, hypothyroid and hyperthyroid rats. Baseline atrial rate and Emax were significantly lower than normal in the hypothyroid group and significantly higher than normal in the hyperthyroid group. Differences between the groups were minimal for pD2 and range of response to noradrenaline. The response to beta-receptor antagonists was the same in all 3 groups with the exception of the hypothyroid group which showed an attenuated increase in baseline atrial rate with compounds possessing partial agonist activity. This was particularly marked for practolol. These results do not provide evidence for an altered responsiveness to catecholamines due to altered thyroid status but suggest that thyroid hormones have a direct action on cardiac tissue.

Adrenergic beta-Antagonists↗
PubMed1978

Mechanism of the hypertensive effect of droperidol in pheochromocytoma.

Droperidol is used in the anaesthetic management of pheochromocytoma because of its sedative, anti-dysrhythmic and alpha-adrenoreceptor blocking properties. However, droperidol when used in pheochromocytoma, has been reported to produce a paradoxical hypertensive response. In vitro experiments with perfused rabbit ear arteries using a histochemical fluorescence technique, showed droperidol to be an inhibitor of noradrenaline uptake into sympathetic nerve endings, and this uptake inhibition was dose related. The uptake inhibition effect did not, however, produce pressor changes in experiments simulating pheochromocytoma in cats. The hypertensive response to droperidol may be due to blockade of presynaptic alpha-adrenoreceptors and this possible mechanism of action is discussed.

Adrenal Gland Neoplasms↗
PubMed1976

Verbal imagery and connotation as memory-induced mediators of aggressive behavior.

Three studies investigated the effects of an information-processing variable (imagery-concreteness) on susceptibility to aggressive stimulation. Study 1 (n=83) results indicated that subjects' rating of imagery level and aggressive connotation for words can be manipulated independently. In study 2 (n=64), manipulations of verbal connotation and verbal imagery indicated that imagery level but not aggressive connotation significantly influenced the delayed recall of the verbal material. In Study 3 (n=60), males in a 2 X 2 between-subjects factorial design first learned lists of words varying in imagery (high or low) and verbal connotation (aggressive or neutral). Next, subjects were given the opportunity to shock their partners as part of a sham learning task. To induce arousal, all subjects learning high-imagery-aggressive word lists delivered significantly more intense shock to their partners. The results were interpreted as supporting an information-processing (memory) analysis of the effects of exposure to aggressive material.

Aggression↗
PubMed1975

Naturalistic studies of aggressive behavior: aggressive stimuli, victim visibility, and horn honking.

Three studies extended laboratory research on aggression to a naturalistic setting which involved horn honking from drivers as a measure of aggression; the studies were adapted from Doob and Gross. The results from a survey (Study 1) of 59 drivers suggested that they were frequently irritated by and aggressive toward other drivers. A second study (using a 3x2 factorial design with 92 male drivers) indicated that manipulations of a rifle in an aggressive context and victim visibility (dehumanization) both significantly influenced horn honking rates subsequent to obstruction at a signal light. A third study with 137 male drivers and 63 female drivers examined the interactive effects of a rifle, an aggressively connotated bumper sticker, and individual subject characteristics (sex and an exploratory index of self-perceived status) on horn honking. The results for three studies in naturalistic settings offer possible extensions of laboratory based findings on aggression. The role of inhibitions in modifying the pattern of results was also discussed.

Aggression↗