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W C Stebbins

Publications and source records attributed to W C Stebbins.

At least 19 recordsLinked to original sources
PubMed1992

Formant frequency discrimination by Japanese macaques (Macaca fuscata).

These studies investigated formant frequency discrimination by Japanese macaques (Macaca fuscata) using an AX discrimination procedure and techniques of operant conditioning. Nonhuman subjects were significantly more sensitive to increments in the center frequency of either the first (F1) or second (F2) formant of single-formant complexes than to corresponding pure-tone frequency shifts. Furthermore, difference limens (DLs) for multiformant signals were not significantly different than those for single-formant stimuli. These results suggest that Japanese monkeys process formant and pure-tone frequency increments differentially and that the same mechanisms mediate formant frequency discrimination in single-formant and vowel-like complexes. The importance of two of the cues available to mediate formant frequency discrimination, changes in the phase and the amplitude spectra of the signals, was investigated by independently manipulating these two parameters. Results of the studies indicated that phase cues were not a significant feature of formant frequency discrimination by Japanese macaques. Rather, subjects attended to relative level changes in harmonics within a narrow frequency range near F1 and F2 to detect formant frequency increments. These findings are compared to human formant discrimination data and suggest that both species rely on detecting alterations in spectral shape to discriminate formant frequency shifts. Implications of the results for animal models of speech perception are discussed.

Adult↗
PubMed1990

Apical hair cells and hearing.

This study assessed the contribution of the apical hair cells to hearing. Guinea pigs, chinchillas and monkeys were behaviorally trained using positive reinforcement to respond to pure-tone stimuli. When a stable audiogram had been determined, each subject received one of three experimental treatments: ototoxic drug administration, low-frequency noise exposure, or the application of a cryoprobe to the bony wall of the cochlear apex. After post-treatment audiograms stabilized, subjects were euthanized and the percentage of hair cells remaining was assessed by light microscopy. Results indicate that a redundancy of encoding mechanisms exist in the mammalian cochlea for low-frequency stimuli. They also suggest that a very small percentage of apical hair cells are sufficient for some low-frequency hearing. Finally, data from this and other studies suggest that the low-frequency threshold shift caused by the loss of a certain percentage of apical hair cells is less pronounced than the high-frequency threshold shift caused by the loss of a comparable percentage of basal hair cells. These data agree with anatomical and electrophysiological evidence that functional as well as anatomical differences may exist between the apex and base of the cochlea.

Animals↗
PubMed1990

Frequency discrimination in the monkey.

This study evaluated frequency discrimination ability in 11 monkeys over an extended period of time using a repeating-standard procedure and the method of constant stimuli. The intersubject variability of the difference limens for frequency (delta F) was large, as reported by other investigators, but similar in magnitude to the variability of the difference limens for intensity (delta I) from three of the same subjects in an intensity discrimination experiment. Continued training generally resulted in a rapid decrease in delta F's, followed by a longer-term, slower decrease. For one subject delta F's slowly decreased throughout a 190-week time period. This long-term training effect was specific to frequency discrimination; a similar effect was not observed for the same subject tested in an intensity discrimination experiment. Finally, delta F's from the well-trained monkeys of this study were larger than monkey delta F's from this laboratory reported in an earlier study, and than human delta F's. An anatomical explanation for the human/monkey delta F magnitude difference is explored.

Animals↗
PubMed1989

Categorical perception of conspecific communication sounds by Japanese macaques, Macaca fuscata.

Field studies indicate that Japanese macaque (Macaca fuscata) communication signals vary with the social situation in which they occur [S. Green, "Variation of vocal pattern with social situation in the Japanese monkey (Macaca fuscata): A field study," in Primate Behavior, edited by L. A. Rosenblum (Academic, New York, 1975), Vol. 4]. A significant acoustic property of the contact calls produced by these primates is the temporal position of a frequency peak within the vocalization, that is, an inflection from rising to falling frequency [May et al., "Significant features of Japanese macaque communication sounds: A psychophysical study," Anim. Behav. 36, 1432-1444 (1988)]. The experiments reported here are based on the hypothesis that Japanese macaques derive meaning from this temporally graded feature by parceling the acoustic variation inherent in natural contact calls into two functional categories, and thus exhibit behavior that is analogous to the categorical perception of speech sounds by humans. To test this hypothesis, Japanese macaques were trained to classify natural contact calls by performing operant responses that signified either an early or late frequency peak position. Then, the subjects were tested in a series of experiments that required them to generalize this behavior to synthetic calls representing a continuum of peak positions. Demonstration of the classical perceptual effects noted for human listeners suggests that categorical perception reflects a principle of auditory information processing that influences the perception of sounds in the communication systems not only of humans, but of animals as well.

Animal Communication↗
PubMed1987

Effects of outer hair cell loss on the frequency selectivity of the patas monkey auditory system.

This report describes a study that took advantage of the unique reactivity of the patas monkey (Erythrocebus patas) to dihydrostreptomycin-sulfate (DHSM) to investigate the effects of selective outer hair cell (OHC) lesions on psychophysical tuning curves (PTC). Four patas monkeys were trained using operant reinforcement techniques to perform forward masking PTCs at frequencies of 500 Hz, 2, 4, and 8 kHz, at 10 dB SL. Steady and pulsed-tone thresholds were also measured from 63 Hz to 40 kHz in half-octave steps. The animals were given daily i.m. injections of DHSM at 20 mg/kg per day until shifts in absolute threshold at 16 kHz exceeded 10 dB, at which time the drug was discontinued. Initial changes in PTC shape included elevations in the tip region associated with the increase in threshold and no elevation or a hypersensitivity of the low-frequency tail region. In general, threshold and therefore PTC tip elevations of at least 40 dB were required before any increase in the low-frequency tail became evident. Following completion of psychophysical testing, animals were sacrificed and cytochochleograms were determined. At frequencies corresponding to regions of complete OHC loss and complete IHC retention a lack of selectivity was evident and PTCs closely resemble low-pass filters. This residual low-pass tuning is similar to that seen in VIIIth nerve fibers in ears devoid of OHCs and in basilar membrane transfer functions from traumatized ears. PTCs taken at frequencies corresponding to areas with no loss of receptors showed no systematic changes in sensitivity or selectivity. Because loss of normal OHC function results in greater than a 50-dB loss in sensitivity, as well as a detuned PTC, these findings strongly support the suggestion that the role of the OHC system is to increase the sensitivity and selectivity of the auditory system.

Animals↗
PubMed1987

The species-specific nature of the ototoxicity of dihydrostreptomycin in the patas monkey.

The remarkable susceptibility of the inner ear of the patas monkey (Erythrocebus patas) to the ototoxic action of dihydrostreptomycin (DHSM) (and streptomycin (SM)) is well established in this paper and affords a rare example of a species-specific reaction to a restricted class of compounds within the aminoglycoside group of antibiotics. In a series of experiments, behavioral and morphological observations together provided the following profile of DHSM ototoxicity in the patas monkey: Sudden onset of hearing loss beginning after 7-9 weeks of treatment; Substantial, though often partial, hearing impairment beginning at the high frequencies and progressing with or without continued treatment to the low frequencies; In the inner ear, a corresponding and selective loss of nerve fibers and of outer hair cells, relative to inner hair cells, beginning in the base of the cochlea and proceeding toward the apex; Continued and progressive loss of hearing for several months after cessation of drug treatment; and Non-auditory effects in some animals on the kidney and vestibular system. Results from control experiments confirmed this special relationship between the patas monkey and DHSM: Other nonhuman primates (macaques and vervet monkeys) were essentially unaffected by DHSM; The patas showed no equivalent sensitivity to other aminoglycosides such as kanamycin or to other forms of ototraumatic insult such as intense noise.

Animals↗
PubMed1979

Hearing thresholds with outer and inner hair cell loss.

Hearing impairment and related cochlear histopathologic changes were evaluated in experimental animals after treatment with aminoglycoside antibiotics or exposure to intense sound. In the course of treatment with kanamycin, neomycin, or dihydrostreptomycin, permanent hearing loss in monkeys and guinea pigs occurred first at the high frequencies and progressed toward the lows. Exposure to different octave bands of noise at 120 dB SPL in monkeys and chinchillas produced permanent hearing loss at frequencies related to the spectral characteristics of the octave band. In most instances loss of outer hair cells was substantially greater than that of inner hair cells. In fact, the pattern and location of missing outer hair cells on the basilar membrane were most often correlated with threshold shifts of 50 dB or less. Generally inner hair cell loss was observed when the threshold shift was greater than 50 dB. Our data support the place principle and the inference that the outer hair cells are essential for hearing from threshold to about 50 dB SL. The inner hair cells, if functioning normally, apparently take over above that level. Although there is little doubt that such a generalization will, in the long term, be found to have been greatly oversimplified, there is every reason to believe that a combination of behavioral and morphologic procedures, as used in this study, will play an important part in elucidating the differences in functional significance of the two types of hair cells.

Animals↗
PubMed1979

Perception of conspecific vocalizations by Japanese macaques. Evidence for selective attention and neural lateralization.

Japanese macaques (Macaca fuscata) and control species (vervet, pigtailed macaque, bonnet macaque) were trained for food to respond to one class of recorded fuscata vocalizations and do not respond to a second class. A measure of neural lateralization was obtained by presenting the stimuli randomly to the right or the left ear, and comparing performance in the two ears (ear advantage method). Vocalizations were from Steven Green's field tapes. In experiment I, the two classes were Green's 'smooth early high coos' (SE) and 'smooth late high coos' (SL). Experiment II utilized the same vocalizations, but sorted into a high-pitched and a low-pitched class, i.e., orthogonally to the communication-relevant dimension. We found that (a) Japanese macaques learned the SE-SL discrimination faster than the pitch discrimination; (b) the reverse was true for the controls; (c) Japanese macaques showed a right-ear advantage (presumed left hemisphere advantage) for the SE-SL distinction, but not for the pitch discrimination, and (d) controls (with one exception) showed no ear advantage for either discrimination. These demonstrations of selective attention to communication-relevant parameters of conspecific vocalizations, and neural lateralization in the perception of these vocalizations, parallel similar findings in human speech perception.

Animals↗
PubMed1979

Comparative behavioral toxicology.

Behavioral conditioning together with conventional sensory testing methods may be used in the evaluation of toxic effects on sensory systems in experimental animal models. Such procedures yield precise quantitative estimates of impairment in absolute and differential acuity and in sensory perception. Additionally, these behavioral changes can be related to the presence of histopathology in peripheral sensory structures; this orderly relation between structure and function may aid in our understanding of the basis for sensory coding in the normal end organ.

Aminoglycosides↗
PubMed1978

Neural lateralization of species-specific vocalizations by Japanese macaques (Macaca fuscata).

Five Japanese macaques and five other Old World monkeys were trained to discriminate among field-recorded Japanese macaque vocalizations. One task required discrimination of a communicatively relevant acoustic feature ("peak"), and a second required discrimination of an orthogonal feature of the same vocalizations ("pitch"). The Japanese animals more proficiently discriminated the peak feature when stimuli were presented to the right ear (primarily left cerebral hemisphere), as opposed to the left ear (primarily right hemisphere). In discriminating the pitch feature, the Japanese animals either showed (i) a left-ear processing advantage or (ii) no ear advantage. The comparison animals, with one exception, showed no ear advantage in processing either feature of the vocalizations. The results suggest that Japanese macaques engage left-hemisphere processors for the analysis of communicatively significant sounds that are analogous to the lateralized mechanisms used by humans listening to speech.

Animals↗
PubMed1978

Localization of primate calls by old world monkeys.

Monkeys (Macaca) were trained by operant conditioning techniques to report the minimum detectable change in location of a sound in space, and were tested with a series of recorded coo or clear call vocalizations. Acuity of localization varied from approximately 4 degrees to 15 degrees and was a function of the magnitude of the change in pitch (frequency modulation) of the different clear calls.

Animals↗
PubMed1978

Hearing loss and cochlear pathology in the monkey (Macaca) following exposure to high levels of noise.

Eight Old World monkeys were exposed 8 h daily for 20 days to octave-band noise having center frequencies from 0.5--8 kHz at levels of 117--120 dB SPL. Two additional animals received exposures to wide-band, 120-dB SPL noise on the same schedule, and one animal was exposed to the 2-kHz octave band for 40 h continuously. Behavioral audiograms were measured throughout exposure and during a 1-month recovery period. Following recovery, the animals were sacrificed and their ears examined histologically. Monaural audiograms are presented showing initial and final TTS and PTS measured at the end of the recovery period. These are compared with complete cytocochleograms for each ear. Hair cell loss was generally restricted to the outer rows, and was reasonably well correlated with pattern of hearing loss. Some cell loss, including inner hair cells, was found in the extreme basal turn, usually without associated high-frequency hearing loss. The relationships between exposure frequency, hearing loss, and locus of cochlear pathology are discussed, as are changes in TTS during exposure.

Animals↗
PubMed1978

Auditory thresholds and kanamycin-induced hearing loss in the guinea pig assessed by a positive reinforcement procedure.

Absolute thresholds from 125 Hz to 52 kHz are determined for six guinea pigs trained by a positive reinforcement method. Four to five hundred trials were conducted during daily testing sessions and little between- or within-subject variability was found. Two of the six animals were subsequently treated with kanamycin and the development of a hearing loss for the high frequencies was followed. Loss of outer and to a lesser extent inner hair cells was well correlated with the threshold shift observed. Contrary to the experience of previous investigators, this operant training procedure has proved as efficient as that for other species of experimental animals, such as the monkey and the chinchilla. It holds excellent promise for future auditory behavioral work with the guinea pig.

Animals↗
PubMed1978

Behavioral ototoxicology.

Methods for the evaluation in experimental animals of toxic substances that produce hearing impairment are described. In the experiments reported here, animals were trained by positive reinforcement operant conditioning procedures so that their hearing could be examined by behavioral means. When normal hearing was established, aminoglycosidic antibiotics (kanamycin and dihydrostreptomycin) were given daily and hearing tests administered in order that the course of hearing loss could be closely followed. Initial loss of sensitivity to the high frequencies always progressed in time to impairment at the low frequencies, and these changes in hearing were correlated with a loss of receptor cells in the inner ear which started in the basal region of the cochlea and advanced toward the apex. Although such behavioral procedures are moderately expensive to instrument and relatively time-consuming to apply, they are shown to yield valid quantitative measures of hearing. Further, they provide for reliable early detection of the toxic process and a measure of behavioral impairment that can be precisely related to the histopathological changes that occur simultaneously in the inner ear and auditory nerve.

Animals↗
PubMed1977

Behavioral system and apparatus for tone-detection and choice reaction times in the cat.

An efficacious operant-conditioning procedure for psychophysical experiments with cats is described. The system features (a) restraint of the cat and the use of the liquid reinforcement delivery cup to control orientation with respect to the stimuli, (b) a minimum of apparatus between the cat and a free-field sound source, (c) two response pedals so that separate "Yes" and "No" responses are defined, (d) a discrete trial procedure with reaction time (RT) defined as the time from the onset of a trial until the occurrence of a response, and (e) an effective liquid reinforcer and simple delivery system. Operation of the system was demonstrated with the method of constant stimuli. Detectability was directly related, and median RT for correct "Yes" responses inversely related, to tone sound pressure.

Animals↗
PubMed1975

Congenital ophthalmoplegia and school achievement: a case study.

A 6 1/2-year-old boy with Moebius' syndrome, with severely restricted horizontal eye movements, was found to have the visuo-motor integration of a child of three years (IQ equivalent 41) and the perceptual development of a child of four years 10 months (perceptual quotient 68). Cognitive assessment revealed functioning in the low dull-normal range of ability (IQ equivalent 83). Achievement in arithmetic and reading was found to be at late kindergarten and early first-grade levels respectively (IQ equivalents 83 and 92). Thus the boy's achievement was in line with his cognitive ability and greater than 1 S.D. above his visual-perception and visuo-motor development. The results of this study replicate the findings of Kalverboer et al. (1970) on a 12-year-old boy with Moebius' syndrome and add to a growing body of evidence which does not support the current emphasis on visuo-motor development and training in the diagnosis and remediation of learning difficulties.

Achievement↗