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P Marler

Publications and source records attributed to P Marler.

At least 19 recordsLinked to original sources
PubMed1997

Enantioselective reduction of 3,4-methylene-dioxyphenylacetone using Candida famata and Zygosaccharomyces rouxii.

In an effort to prepare 3,4-methylene-dioxyphenyl-(S)-isopropanol from 3,4-methylene-dioxyphenylacetone, an initial screen of microbes indicated that Candida famata could catalyze this reaction efficiently at low substrate concentration. A dilute, large-scale process was developed to provide experimental material for the chemical synthesis to be explored. However, the productivity number of this process [0.134 g product (g wet weight cells)-1 day-1 was too low to be practical. C. famata was also extremely sensitive to concentrations of both the ketone and the alcohol greater than 2 g/l. A more extensive screen of yeast and fungi revealed that Zygosaccharomyces rouxii was more tolerant to higher substrate concentrations and had a higher productivity number [0.8 g (g wet weight cells)-1 day-1]. These characteristics suggested that Z. rouxii could be used in a large-scale process at high substrate concentrations.

Acetone↗
PubMed1995

Testosterone-induced shortening of the storage phase of song development in birds interferes with vocal learning.

Bird song is a complex, learned behavior. Vocal learning in sparrows involves several different processes that occur in a distinct temporal pattern over the course of the first year of life. Songs are acquired without practice during a sensitive period within the first 3 months of life and rehearsal of the acquired song does not begin until 7 or 8 months of age. The function of the storage period between song acquisition and production is not known. We set out to investigate its significance by administering testosterone, known to stimulate production of adult song, to birds at 100 days of age after song acquisition was completed but some 5 months prior to normal song onset. Most testosterone-treated birds produced abnormal songs resembling those of males raised in acoustic isolation suggesting that, in sparrows, events occurring during the storage phase play a significant role in vocal learning.

Animals↗
PubMed1994

Selection-based learning in bird song development.

Bird song is a model system for study of the neurobiology, development, and functions of learned vocal communication signals. Research on avian song learning has been dominated by an instructive model of learning--the sensorimotor model. Developmental plasticity is assumed to be based on the incorporation of novel material into the song repertoire. Experimental evidence now indicates an alternative form of plasticity operating in harmony with sensorimotor learning, based on principles of selection, rather than instruction. Song dialects, a common consequence of vocal learning, can be achieved by overproduction of previously memorized songs and selective attrition of those that fail to match the dialect of interacting males. These distinct processes of learning have important implications for study of the neural substrates underlying song production and perception and for efforts to interpret patterns of geographic variation in song.

Aging↗
PubMed1992

Androstenedione therapy reinstates normal, not supernormal, song structure in castrated adult male zebra finches.

In previous studies, androstenedione (AE) replacement therapy restored the highest levels and intensities of courtship song displays in castrated male zebra finches of any hormone tested. Furthermore, female zebra finches responded strongly to AE-treated males and preferred intact males given small AE implants to unsupplemented males. In this study, we asked whether AE treatment might alter song structure, since male song is an important cue in mate choice by female zebra finches. Songs of adult males were recorded. The males were then castrated and given AE therapy and recorded again. No differences were found between the courtship or undirected songs males sang before castration and after AE treatment. As in previous studies, the structure of a male's courtship song differed significantly from his undirected song, and the structural differences between these two song types were not altered by AE treatment.

Androstenedione↗
PubMed1991

Song-learning behavior: the interface with neuroethology.

Behavioral studies of song learning in birds continue to raise new problems for neuroethological investigation. Evidence is emerging for a new form of vocal plasticity, called 'action-based learning'. Motor patterns are overproduced during a particular phase of ontogeny, and are then subjected to attrition and selective reinforcement by various kinds of social stimulation as the young bird matures. This form of learning, analogous to operant conditioning, can occur at phases of development when the more traditional form of 'memory-based learning' is no longer possible. There is evidence that different physiological mechanisms are involved in the development and the maintenance of mature singing, with a transition occurring at the time of song crystallization. Neural events associated with the developmental stabilization of motor patterns are worthy of more study.

Animals↗
PubMed1990

Song learning: the interface between behaviour and neuroethology.

The high degree of developmental plasticity displayed by the songs of oscine birds makes them appropriate subjects for research on the etiology and neurobiology of vocal learning. Strong individual differences and learned local dialects are common. The readiness to acquire new songs appears to persist throughout life in some species and is restricted to relatively short sensitive periods in others. Learning can occur with remarkably few exposures to song. Mimicry of other species occurs but, given a choice, there is a tendency to favour conspecific songs. Evidence is presented for two kinds of vocal learning, one 'memory-based', the other 'action-based.' Subsong and 'plastic song' phases of motor development appear to be obligatory steps in the ontogeny of learned songs. A case is made that acquisition and production should be viewed as distinct phenomena with different physiological correlates. Research on behavioural development is closely associated with studies of the physiology of development. The two are mutually synergistic, and the synergism is well displayed in research on song learning in birds. This review of some of the characteristics of avian vocal learning as derived from behavioural studies, indicates lacunae in our knowledge about the ethology of song learning, and suggests how the comparative study of vocal development can pave the way for new insights into the underlying neurobiology.

Aging↗
PubMed1990

Innate learning preferences: signals for communication.

Research on the ways in which different species of birds learn to sing is used to illustrate the necessity of taking innate factors into account in studies of behavioral development. Experiments on two species of songbirds are described that reveal innate species differences in responsiveness to tape-recorded songs. Conspecific songs are favored over those of other species. These patterns of innately varying responsiveness provide a basis for the development, not of stereotyped behavior, but of variable, individually learned behavior. The viewpoint is presented that mechanisms that differ innately from species to species, some with general functions, others specialized for particular ontogenetic assignments, provide the necessary substrates with which experience interacts.

Animal Communication↗
PubMed1990

Song acquisition in photosensitive and photorefractory male European starlings.

We tested the ability of 1-year-old European starlings (Sturnus vulgaris) to acquire songs while in different physiological states. Photorefractory males, with low testosterone levels, learned songs as completely and as accurately as photosensitive males in full reproductive condition. This indicates that song acquisition in 1-year-old males does not depend on high levels of androgens. The ability to learn songs during the nonbreeding season may reflect the high song output of potential tutors through most of the year, including the photorefractory period, and may facilitate increases in song repertoire size in adulthood.

Animals↗
PubMed1989

Categorical perception of a natural stimulus continuum: birdsong.

A fundamental issue in perception and communication is how continuously varying stimuli are partitioned into discrete categories. In swamp sparrow songs, note duration is a critical feature distinguishing two note categories with different roles in song construction. Pairs of songs with initial notes from different categories contrast more in their effects on territorial males than song pairs with initial notes differing by the same amount but taken from within one note category. The results indicate categorical perception by wild swamp sparrows.

Animal Communication↗
PubMed1989

Addition of song-related neurons in swamp sparrows coincides with memorization, not production, of learned songs.

During song learning in birds, neurons are added to some song nuclei and lost from others. Previous studies have been unable to distinguish whether these neural changes are uniquely associated with memorizing a song model (sensory acquisition) or vocal practice (sensorimotor learning). In this study we measured changes in neuron number within song nuclei of swamp sparrows, a species in which the two phases of song learning are nonoverlapping. Male swamp sparrows were collected as hatchlings and tape-tutored from approximately 22 to 62 days of age. Swamp sparrows memorize about 60% of their song material during this period, but do not begin practicing this learned material until approximately 275 days of age. Birds were sacrificed at 23, 41, 61, 71, 274, or 340 days of age. During sensory acquisition, neuron number increased drastically in both the caudal nucleus of the ventral hyperstriatum (HVc) and Area X. The period of sensorimotor learning was not associated with any further changes in neuron number within these regions. We were unable to detect any significant changes in neuron number within the magnocellular nucleus of the neostriatum or the robust nucleus of the archistriatum during either stage of song learning. These results raise the possibility that ongoing addition of HVc and Area X neurons may encourage, and thereby temporally restrict, song acquisition.

Aging↗
PubMed1988

Alarm signals in birds: the role of testosterone.

In the laboratory and under semi-naturalistic conditions, male domestic fowl (Gallus gallus) produce more alarm calls in response to predatory birds flying overhead than females. This study tests the hypothesis that testosterone is a factor in the control of aerial alarm call production. Birds were castrated early in life and tested as adults in the laboratory. Aerial predators were simulated by cardboard silhouettes drawn overhead. Blood samples were taken at intervals and plasma testosterone levels were measured by radioimmunoassay. Each subject was tested in four conditions: with an empty Silastic implant, with a testosterone-filled implant, with an additional testosterone implant, and after removal of the implants. Results show that the presence of testosterone increases the production of aerial alarm calls, and that removal of the hormone supply results in a drop in calling rate. As a control a second vocal system, food calling, was considered. In contrast with alarm calling, there was no correlation between testosterone levels and variation in food-call production. We conclude that testosterone plays a specific role in activation of the production by cockerels of vocalizations that signal the presence of aerial predators.

Animals↗
PubMed1988

Audience effects on alarm calling in chickens (Gallus gallus).

The male domestic chicken (Gallus gallus) has been found to modulate the production of vocal signals in response to the presence or absence of a suitable audience. We investigated effects on alarm calling by presenting overhead predator models to cockerels in the presence of a variety of social companions. The production of aerial predator calls in response to hawk silhouettes varied with the presence or absence of a member of the same species. The kinds of audience investigated included the mate, unfamiliar females, other females and males with which subjects had had prior visual and auditory contact, and broody hens with and without young. Domestic chicks, unrelated to the subjects, were almost as effective an audience as conspecific adults. A member of another species, however, failed to potentiate alarm-call production. The subjects gave more alarm calls when they were in the presence of either a male or a female audience than when they were alone. By manipulating the visibility of overhead predator models to the subjects and to the audience, we showed that the subjects were not cued by alarm and escape behaviors of the audience. Comparisons with food calling indicate that, in deciding whether to emit a signal in response to the appropriate referent (e.g., food or predators), chickens respond to subtle differences in the nature of the audience with behaviors that vary from one communicative context to another.

Animals↗
PubMed1987

Response of sparrows to songs of deaf and isolation-reared males: further evidence for innate auditory templates.

Adult song sparrows (Melospiza melodia) were tested for response to songs of conspecific males that had been reared in acoustic isolation or deafened early in life. Territorial males responded more aggressively to playback of songs of isolated males than to songs of deafened males but did not discriminate between songs of deafened males and heterospecific songs. Captive females showed an identical pattern when their response was measured in terms of the number and intensity of courtship displays evoked by song. The results support the auditory template theory of song development in demonstrating that species-identifying features are present in songs of isolates and in showing that males unable to hear their own song production do not incorporate these species-identifying features into their songs.

Animals↗
PubMed1987

Correlations between song acquisition, song production, and plasma levels of testosterone and estradiol in sparrows.

Male birdsong is a sexually dimorphic behavior characterized by learned dialects. In a combined study of learning in relation to steroid levels in the plasma, changes in estradiol and testosterone levels were correlated with the timing of the sensitive period for song acquisition and with successive stages in song development. Male swamp sparrows were trained with a changing series of live singing tutors from 26 days to 1 year of age. Song acquisition was concentrated between 26 and 47 days of age (57%). By 85 days of age 71% of acquisition was completed; some occurred as late as 300 days. There were two major periods when testosterone levels were elevated. The first, from 30-80 days, encompassed most of the period of song acquisition. The second, from 260 to at least 360 days of age, coincided with song development. Estradiol levels were elevated from 18 to 170 days of age, encompassing almost all of the period of song acquisition. A marked estradiol peak between 40 and 50 days coincided with a trough in testosterone levels and a hiatus in song acquisition. The strong correlation between the second period of elevated testosterone and song motor development suggests a causal connection, with levels peaking in mid-development and declining during mature song production. Estradiol levels were elevated at the start of the study and remained so during early subsong production, from 30 to 165 days. They then fell to baseline, remaining there throughout the resumption of subsong and plastic song production at 250-326 days. Both estradiol and testosterone are candidates for possibly affecting song acquisition.

Aging↗
PubMed1983

Song structure without auditory feedback: emendations of the auditory template hypothesis.

Motor patterns of songs of swamp and song sparrows, Melospiza georgiana and M. melodia, deafened early in life display a significant degree of species-specific structure. Normal songs of the two species differ in the degree to which they are segmented. Swamp sparrow song consists of a single segment, and song sparrow songs are multisegmental. Song and swamp sparrows were deafened at 17 to 23 days, prior to the onset of song or subsong. The song sparrows developed more segments in their singing than the swamp sparrows. Species-specific trends were also evident in song durations and frequency characteristics. Abnormalities were found, however, in the morphology of the notes and syllables from which songs of early deafened sparrows are constructed. These results require emendation of the auditory template hypothesis of song learning in birds.

Animals↗
PubMed1982

Developmental overproduction and selective attrition: new processes in the epigenesis of birdsong.

All phases of song development from infancy to adulthood were studied intensively in a group of laboratory-reared birds. Male swamp sparrows, Melospiza georgiana, trained with tape-recorded songs in infancy, developed song some 8 months later, averaging 2.2 song types per bird. Analysis of the intermediate stage of plastic song revealed that the birds generated 4 to 5 times more song material than was needed for the species-specific song repertoire. The excess was discarded at the time of full song crystallization. Indications that the attrition process is selective include tendencies to retain imitated rather than nonimitated elements, and the rejection of heterospecific elements. Attrition may also be influenced by vocal stimulation at the time of song crystallization, providing an opportunity for behavioral adjustment even though new themes can no longer be learned. Attrition has been described in the transition in human infants from babbling to speech.

Animals↗