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Biomedical subjects

M D Beecher

Publications and source records attributed to M D Beecher.

At least 19 recordsLinked to original sources
PubMed2000

Lesions of the anterior forebrain song control pathway in female canaries affect song perception in an operant task.

We tested whether the avian anterior forebrain pathway functions in song perception in female canaries, and whether it is specialized for conspecific song perception or functions more generally in auditory perception. Using operant conditioning methods, we trained female canaries to discriminate among synthetic sound stimuli, canary songs, and song sparrow songs. We also trained each bird to discriminate among visual stimuli to test for general effects of lesions on performance. When canaries had learned the discrimination tasks, bilateral electrolytic lesions of the lateral portion of the magnocellular nucleus of the anterior neostriatum (lMAN) were made. The lesioned birds were then tested on the previously learned discrimination tasks. Lesions that destroyed most or all of lMAN decreased the ability of female canaries to discriminate between previously learned pairs of acoustic stimuli of all types, while visual discrimination was unaffected. These results suggest that the female canary anterior forebrain pathway contributes to the perception of acoustic stimuli, with this contribution including heterospecific song and other acoustic stimuli as well as canary song.

Acoustic Stimulation↗
PubMed1998

Auditory perception following hair cell regeneration in European starling (Sturnus vulgaris): frequency and temporal resolution.

Behavioral detection thresholds, auditory filter widths, and temporal modulation transfer functions were obtained from four starlings before, during and after 11 days of subcutaneous injections of kanamycin, an aminoglycoside antibiotic. Birds were operantly conditioned to respond to pure tones and amplitude modulated noises ranging in frequency from 0.25 to 7 kHz using adaptive staircase procedures and were tested daily for 92 days after the first injection of aminoglycoside. All birds had threshold shifts of at least -60 dB at frequencies above 4 kHz. Lower frequencies were affected in some birds, although none of the birds had hearing loss below 3 kHz. All four birds had wider auditory filters at 5 kHz immediately after the aminoglycoside series. Any changes in frequency resolution at frequencies below 5 kHz were slight, transitory, and rarely observed. Two of the four birds had permanently wider auditory filters at 5 kHz. Temporal modulation transfer functions were briefly affected in two birds during the time of greatest threshold shift. Recovery of detection thresholds began soon after the injections ceased and continued for approximately 60 days. Recovery in frequency resolution lagged behind auditory threshold by about 10 days. Normal temporal resolution was observed in the context of impaired intensity and frequency resolution. Changes in auditory threshold and frequency resolution were closely associated for all birds at 5 kHz, but were correlated with statistical significance in only two birds. Scanning electron microscopy was performed on all four birds after 90 days of recovery and confirmed that the extent of initial damage was consistent with the pattern of observed hearing loss.

Animals↗
PubMed1997

Seasonal changes in testosterone, neural attributes of song control nuclei, and song structure in wild songbirds.

Seasonal changes in the neural attributes of brain nuclei that control song in songbirds are among the most pronounced examples of naturally occurring plasticity in the adult brain of any vertebrate. The behavioral correlates of this seasonal neural plasticity have not been well characterized, particularly in songbird species that lack adult song learning. To address this question, we investigated the relationship between seasonal changes in gonadal steroids, song nuclei, and song behavior in adult male song sparrows (Melospiza melodia). At four times of the year, we measured plasma concentrations of testosterone, neural attributes of song nuclei, and several aspects of song structure in wild song sparrows of a nonmigratory population. We found seasonal changes in the song nuclei that were temporally correlated with changes in testosterone concentrations and with changes in song stereotypy. Male song sparrows sang songs that were more variable in structure in the fall, when testosterone concentrations were low and song nuclei were small, than in the spring, when testosterone concentrations were higher and song nuclei were larger. Despite seasonal changes in the song nuclei, the song sparrows continued to sing the same number of different song types, indicating that changes in the song nuclei were not correlated with changes in song repertoire size. These results suggest that song stereotypy, but not repertoire size, is a potential behavioral correlate of seasonal plasticity in the avian song control system.

Animals↗
PubMed1997

Bird song learning as an adaptive strategy.

Parallels are often drawn between bird song learning and human language learning. The analogies include an early sensitive period for learning, separation of sensory and motor phases of learning, 'innate knowledge' of language or song, and specialized neural systems. Nevertheless, in distinction to human language learning, song learning is usually viewed as a purely auditory process. This view is implied in the typical experimental paradigm for studying song learning, in which the bird is isolated in a sound-proof chamber and exposed only to tape-recorded song. This paradigm remains the major method of studying song learning despite recent demonstrations of the importance of social variables, and it contains the implicit assumption that non-auditory variables, especially social and ecological variables, play only a minor role in this process. I will argue here that understanding the functions of song learning requires that we investigate it in the field, where social and ecological variables have full play. We have done just this for the song sparrow, and when viewed in this perspective song learning in the song sparrow takes on the clear outlines of an adaptive strategy.

Adaptation, Psychological↗
PubMed1995

Regenerated hair cells in the European starling: are they more resistant to kanamycin ototoxicity than original hair cells?

Previous work from our laboratory [Marean et al. (1993) Hear. Res. 71, 125-136] has shown that a 10 day dose of 200 mg/kg/day kanamycin produced damage to the basal 34% of the starling basilar papilla. We also observed that repeating the dosing schedule following a 4 month survival period resulted in significantly less damage to the regenerated auditory epithelium. The present study investigated whether or not this apparent resistance was the result of a tendency for regenerated hair cells to be less susceptible to kanamycin ototoxicity, or if other, systemic factors may be involved. Eight European starlings were given subcutaneous injections of 200 mg/kg/day kanamycin for 10 days. Serum levels of kanamycin were measured at the time of sacrifice for all birds, and the basilar papillae of all birds were examined by scanning electron microscopy (SEM). Two of these birds (Group 1) were sacrificed immediately following the dosing period. Two of the birds were allowed to survive for 60 days (Group 2). Two of the birds were redosed with 200 mg/kg/day for 10 days after 60 days survival (Group 3). Finally, two birds were redosed with 250 mg/kg/day until serum levels of kanamycin were the same as Group 1 when sacrificed (> 9 micrograms/ml). The SEM results showed that the regenerated auditory epithelium of the birds dosed a second time sustained less damage compared to previously untreated ears, even though the dosing regimen was the same (Group 3 versus Group 1). The regenerated auditory epithelium of birds dosed a second time sustained the same damage as previously untreated animals when the dosage was increased to attain similar serum levels (Group 4 versus Group 1). These results suggest metabolic changes occur in the starling in response to the initial dose of kanamycin which do not necessarily involve changes in hair cell resistance to ototoxicity.

Animals↗
PubMed1994

Correlation of song learning and territory establishment strategies in the song sparrow.

In a field study, we show that a young song sparrow (i) selects his songs from three or four older birds who have neighboring territories, (ii) preferentially learns song types that these tutor neighbors share, and (iii) ultimately sets up his territory next to, or replaces, one of these tutor neighbors. The consequence of this song learning strategy is that the young bird's song repertoire represents the "logical intersection" of the song repertoires of his tutor neighbors. We argue that this repertoire is optimally designed for mimicry (sounding like your neighbors) and for communication between neighbors (song sparrows address or reply to a neighbor with a song they share with that neighbor).

Journal Article↗
PubMed1993

Hair cell regeneration in the European starling (Sturnus vulgaris): recovery of pure-tone detection thresholds.

Behavioral detection thresholds were obtained from four starlings before, during, and after 11 days of subcutaneous injections of kanamycin. Birds were operantly conditioned to respond to pure-tones ranging in frequency from 0.25 kHz to 7 kHz using the method of constant stimuli and were tested daily for 141 days after the first injection of aminoglycoside. All four birds sustained hearing losses greater than 60 dB at frequencies from 4 kHz to 7 kHz by the end of the 11 day injection schedule. Two birds had a slight shift in threshold at 3 kHz. No change in threshold occurred for any of the birds at lower frequencies. Recovery of detection thresholds began soon after the injections ceased and continued for approximately 50 days. In all four birds there was some degree of permanent hearing loss: 5 dB to 15 dB at frequencies between 4 kHz and 6 kHz, and approximately 25 dB at 7 kHz. Scanning electron microscopy (SEM) was performed at 0 and 5 days post-injection in a separate group of starlings given the same injection schedule. Hair cell loss and damage was observed across the basal 34% to 36% of the basilar papilla. SEM in two behaviorally tested birds sacrificed 142 days after the first injection showed that there was regeneration of hair cells to populate the previously damaged region, but that disorientation of stereocilia bundles in the basal third of the basilar papilla was common. The other two behaviorally tested birds were treated with kanamycin again for 16 days beginning at 142 days after the first injection. Thresholds shifted again, but less than during the first dosing period. SEM of these birds' basilar papillae showed less hair cell loss than observed in the birds given only a single, 11 day dosing of kanamycin. This result suggests that birds may be less susceptible to the ototoxic effects of kanamycin in repeated treatments. In all four birds, the degree and position of damage observed with SEM corresponded with the extent and frequency of hearing loss.

Acoustic Stimulation↗
PubMed1992

Perception of cliff swallow calls by birds (Hirundo pyrrhonota and Sturnus vulgaris) and humans (Homo sapiens).

We tested for species differences in the perception of the cliff swallow chick begging call. One cliff swallow (Hirundo pyrrhonota), 3 European starling (Sturnus vulgaris), and 3 human (Homo sapiens) subjects were trained on go-no-go or repeating background tasks to discriminate between all possible stimulus pairs, measured by percentage of correct response and latency. We used multidimensional scaling to convert the similarity measures into a 2-dimensional map for each subject. Most of the maps were significantly correlated in Dimension 1 but not in Dimension 2. A cluster analysis separated bird and human maps. To identify the most important acoustic cues for each subject, we regressed the coordinates of each dimension on acoustic variables measured from the stimuli. For all subjects, center frequency was Dimension 1. Different acoustic cues were associated with Dimension 2, with agreement only on bandwidth, by the cliff swallow and 1 starling.

Animal Communication↗
PubMed1986

Acoustic adaptations for parent-offspring recognition in swallows.

We have used field and laboratory studies to investigate acoustic adaptations for parent-offspring recognition in two closely related pairs of swallows: (a) bank swallow (Riparia riparia) and northern rough-winged swallow (Stelgidopteryx serripennis), and (b) cliff swallow (Hirundo pyrrhonota) and barn swallow (Hirundo rustica). Cross-fostering and playback experiments show that bank swallow and cliff swallow parents recognize their offspring by voice while rough-winged swallow and barn swallow parents do not. We argue that this species difference is due to an evolutionary history of strong selection for recognition in bank swallows and cliff swallows, which live in large, dense colonies, and of weak or no selection for recognition in rough-winged swallows and barn swallows, which live solitarily or in small groups. We consider two possible acoustic adaptations which may underlie the observed species difference. First, the "signature" calls of cliff swallow and bank swallow chicks appear to be more individually distinctive than the homologous calls of rough-winged swallows and barn swallows. This conclusion is supported by a sonographic analysis of among- and within-individual call variation: The information content of bank swallow and cliff swallow calls is considerably greater than that of rough-winged swallow or barn swallow calls. We also discuss our more recent work on the hypothesis that the colonial swallow species are better able to discriminate these sorts of auditory stimuli. We conclude with the caution that auditory specializations may be unnecessary given the signature call adaptation and the general capabilities of the avian ear.

Animal Communication↗
PubMed1984

Neural lateralization of vocalizations by Japanese macaques: communicative significance is more important than acoustic structure.

The study was designed to determine whether the neural lateralization of vocal perception in Japanese macaques depends on the acoustic properties of the calls used or their communicative significance. Four monkeys--two Japanese macaques and two comparison macaques--were trained to discriminate among monaurally presented exemplars of two classes of vocalizations from the Japanese macaque's repertoire. Once the subjects mastered the discrimination, they performed at equivalent accuracy levels for 150 sessions. However, during this time the Japanese monkeys showed a right ear performance advantage, whereas the comparison monkeys showed no ear advantage. In order to assess whether the comparison and Japanese monkeys were attending to the same acoustic cue when performing the discrimination, a generalization test was conducted with 27 novel vocalizations. The individual monkeys' generalization gradients were highly similar and revealed that all subjects were in fact listening to the same feature of the calls. These findings, coupled with the fact that the calls were of biological significance to the Japanese monkeys alone, suggest that the laterality effect is related, in some fashion, to the communicative valence of the signals rather than their purely physical characteristics.

Animals↗
PubMed1980

Localization of noise bands by Old World monkeys.

The acuity of auditory localization in Old World monkeys (Macaca) was determined psychophysically for 44 noise bands graded in bandwidth and center frequency. The acuity of localization was assessed through the method of constant stimuli under free-field conditions in an anechoic chamber. Monkeys were trained through positive-reinforcement operant-conditioning procedures to report a change in azimuth of the signal by releasing a response disk. The results show that localization thresholds are dependent upon the bandwidth of the signal over much of the macaque's range of audibility. Thresholds for the detection of a change in location varied from 18 degrees (for a signal 250 Hz in bandwidth centered at 11 200 Hz) to 4 degrees (for a signal 8000 Hz in bandwidth centered at 8000 Hz). The results suggest that the localization of spectrally complex signals is determined by a mechanism sensitive to periodicity (time-domain) information across the monkey's range of audibility.

Animals↗
PubMed1979

Species-specific perceptual processing of vocal sounds by monkeys.

Monkeys of four species were trained to discriminate between sets of natural tonal calls of Japanese macaques (Macaca fuscata) by the position of a frequency-inflection peak or by initial pitch. The Japanese macaques consistently performed best on peak position and the other species on pitch. The results imply special strategies for perceptional processing of vocal sounds and suggest parallels with human speech perception.

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↗
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↗
PubMed1976

Rate-dependent effect of amphetamine in rats: extension to between-subjects effect.

Following either variable-interval or fixed-interval training. 20 rats received both 0.5 and 2.0 mg/kg of amphetamine. For both schedules, amphetamine decrease response rates of high-rate subjects and increased those of low-rate subjects. Within-subject analysis of fixed-interval rates revealed the same rate-dependent effect. It is suggested that the between-subject and within-subject effects may have the same basis.

Animals↗