Song learning: the interface between behaviour and neuroethology

The use of artificial songs to assess song recognition in imprinted female songbirds: a concept proposal

We propose an experimental paradigm to examine acoustic features responsible for song preference and recognition in songbirds. Song preference in female songbirds is often influenced by early song experience. That is why several Estrildid species, including our subject species, the Java sparrow (Padda oryzivora), are known to show an imprinted preference for their father's songs. After confirming that Java sparrow females preferred their father's song compared to non-imprinted through song playbacks (first step), we repeated the playback tests in the same subjects using synthesized stimuli (second step). To create synthesized stimuli, we removed all the complex frequency modulations and subharmonics from song notes that we used for the first step playback tests to see the effect of spectrometric features on song recognition. The results indicated that females showed higher rate of calling towards synthesized father song stimuli, suggesting that the macroscopic patterns would play more important roles in song recognition than the microscopic acoustic features. Although we looked at spectrometric features and father-imprinted song preference in this study, similar testing can be applied in many ways to test preference for local dialects or subspecies-specific songs.

Musicality in human vocal communication: an evolutionary perspective

Studies show that specific vocal modulations, akin to those of infant-directed speech (IDS) and perhaps music, play a role in communicating intentions and mental states during human social interaction. Based on this, we propose a model for the evolution of musicality-the capacity to process musical information-in relation to human vocal communication. We suggest that a complex social environment, with strong social bonds, promoted the appearance of musicality-related abilities. These social bonds were not limited to those between offspring and mothers or other carers, although these may have been especially influential in view of altriciality of human infants. The model can be further tested in other species by comparing levels of sociality and complexity of vocal communication. By integrating several theories, our model presents a radically different view of musicality, not limited to specifically musical scenarios, but one in which this capacity originally evolved to aid parent-infant communication and bonding, and even today plays a role not only in music but also in IDS, as well as in some adult-directed speech contexts. This article is part of the theme issue 'Voice modulation: from origin and mechanism to social impact (Part II)'.

Evidence for Teaching in an Australian Songbird

Song in oscine birds (as in human speech and song) relies upon the rare capacity of vocal learning. Transmission can be vertical, horizontal, or oblique. As a rule, memorization and production by a naïve bird are not simultaneous: the long-term storage of song phrases precedes their first vocal rehearsal by months. While a wealth of detail regarding songbird enculturation has been uncovered by focusing on the apprentice, whether observational learning can fully account for the ontogeny of birdsong, or whether there could also be an element of active teaching involved, has remained an open question. Given the paucity of knowledge on animal cultures, I argue for the utility of an inclusive definition of teaching that encourages data be collected across a wide range of taxa. Borrowing insights from musicology, I introduce the Australian pied butcherbird (Cracticus nigrogularis) into the debate surrounding mechanisms of cultural transmission. I probe the relevance and utility of mentalistic, culture-based, and functionalist approaches to teaching in this species. Sonographic analysis of birdsong recordings and observational data (including photographs) of pied butcherbird behavior at one field site provide evidence that I assess based on criteria laid down by Caro and Hauser, along with later refinements to their functionalist definition. The candidate case of teaching reviewed here adds to a limited but growing body of reports supporting the notion that teaching may be more widespread than is currently realized. Nonetheless, I describe the challenges of confirming that learning has occurred in songbird pupils, given the delay between vocal instruction and production, as well as the low status accorded to anecdote and other observational evidence commonly mustered in instances of purported teaching. As a corrective, I press for an emphasis on biodiversity that will guide the study of teaching beyond human accounts and intractable discipline-specific burdens of proof.

Variable but not random: temporal pattern coding in a songbird brain area necessary for song modification

Practice of a complex motor gesture involves motor exploration to attain a better match to target, but little is known about the neural code for such exploration. We examine spiking in a premotor area of the songbird brain critical for song modification and quantify correlations between spiking and time in the motor sequence. While isolated spikes code for time in song during performance of song to a female bird, extended strings of spiking and silence, particularly bursts, code for time in song during undirected (solo) singing, or "practice." Bursts code for particular times in song with more information than individual spikes, and this spike-spike synergy is significantly higher during undirected singing. The observed pattern information cannot be accounted for by a Poisson model with a matched time-varying rate, indicating that the precise timing of spikes in both bursts in undirected singing and isolated spikes in directed singing code for song with a temporal code. Temporal coding during practice supports the hypothesis that lateral magnocellular nucleus of the anterior nidopallium neurons actively guide song modification at local instances in time.NEW & NOTEWORTHY This paper shows that bursts of spikes in the songbird brain during practice carry information about the output motor pattern. The brain's code for song changes with social context, in performance versus practice. Synergistic combinations of spiking and silence code for time in the bird's song. This is one of the first uses of information theory to quantify neural information about a motor output. This activity may guide changes to the song.

Auditory event-related potentials index faster processing of natural speech but not synthetic speech over nonspeech analogs in children

Given the crucial role of speech sounds in human language, it may be beneficial for speech to be supported by more efficient auditory and attentional neural processing mechanisms compared to nonspeech sounds. However, previous event-related potential (ERP) studies have found either no differences or slower auditory processing of speech than nonspeech, as well as inconsistent attentional processing. We hypothesized that this may be due to the use of synthetic stimuli in past experiments. The present study measured ERP responses during passive listening to both synthetic and natural speech and complexity-matched nonspeech analog sounds in 22 8-11-year-old children. We found that although children were more likely to show immature auditory ERP responses to the more complex natural stimuli, ERP latencies were significantly faster to natural speech compared to cow vocalizations, but were significantly slower to synthetic speech compared to tones. The attentional results indicated a P3a orienting response only to the cow sound, and we discuss potential methodological reasons for this. We conclude that our results support more efficient auditory processing of natural speech sounds in children, though more research with a wider array of stimuli will be necessary to confirm these results. Our results also highlight the importance of using natural stimuli in research investigating the neurobiology of language.

Anthropogenic noise affects winter song structure of a long-distance migrant, Gambel’s white-crowned sparrow

Many animals learn to produce acoustic signals that are used to attract mates and defend territories. The structure of these signals can be influenced by external features of the environment, including the anthropogenic soundscape. In many sedentary species, habitat features and soundscape appears to influence the cultural evolution of songs, often with tradeoffs for better transmission over sexually selected song structure. However, none have investigated whether noise on the wintering grounds affects song structure, which for long-distance migrants may result in an acoustic ‘mismatch’ when returning to a breeding ground. This study investigates urban noise effects on song structure in a long-distance migrant, Zonotrichia leucophrys gambelii, on the wintering grounds in the Fresno Clovis Metropolitan Area and in outlying non-urban areas. Songs and background noise levels were recorded concurrently, and song measurements of frequency and duration were examined differences across noise levels and habitats . We found that the buzz and trill decrease in bandwidth in the presence of noise. The length of the whistle and buzz portion of the song also tends to decreases with noise in urban habitats. This trend toward short, pure tones in noisy areas may transmit better in noisy urban winter habitats, but may not be adaptive on quieter breeding grounds. We suggest that future studies should consider whether winter auditory feedback and song learning environments have consequences for song crystallization and breeding success for long-distance migrants.

Correlated evolution between repertoire size and song plasticity predicts that sexual selection on song promotes open-ended learning

Some oscine songbird species modify their songs throughout their lives ('adult song plasticity' or 'open-ended learning'), while others crystallize their songs around sexual maturity. It remains unknown whether the strength of sexual selection on song characteristics, such as repertoire size, affects adult song plasticity, or whether adult song plasticity affects song evolution. Here, we compiled data about song plasticity, song characteristics, and mating system and then examined evolutionary interactions between these traits. Across 67 species, we found that lineages with adult song plasticity show directional evolution toward increased syllable and song repertoires, while several other song characteristics evolved faster, but in a non-directional manner. Song plasticity appears to drive bi-directional transitions between monogamous and polygynous social mating systems. Notably, our analysis of correlated evolution suggests that extreme syllable and song repertoire sizes drive the evolution of adult song plasticity or stability, providing novel evidence that sexual selection may indirectly influence open- versus closed-ended learning.

Neurotensin and neurotensin receptor 1 mRNA expression in song-control regions changes during development in male zebra finches

Learned vocalizations are important for communication in some vertebrate taxa. The neural circuitry for the learning and production of vocalizations is well known in songbirds, many of which learn songs initially during a critical period early in life. Dopamine is essential for motor learning, including song learning, and dopamine-related measures change throughout development in song-control regions such as HVC, the lateral magnocellular nucleus of the anterior nidopallium (LMAN), Area X, and the robust nucleus of the arcopallium (RA). In mammals, the neuropeptide neurotensin strongly interacts with dopamine signaling. This study investigated a potential role for the neurotensin system in song learning by examining how neurotensin (Nts) and neurotensin receptor 1 (Ntsr1) expression change throughout development. Nts and Ntsr1 mRNA expression was analyzed in song-control regions of male zebra finches in four stages of the song learning process: pre-subsong (25 days posthatch; dph), subsong (45 dph), plastic song (60 dph), and crystallized song (130 dph). Nts expression in LMAN during the subsong stage was lower compared to other time points. Ntsr1 expression was highest in HVC, Area X, and RA during the pre-subsong stage. Opposite and complementary expression patterns for the two genes in song nuclei and across the whole brain suggest distinct roles for regions that produce and receive Nts. The expression changes at crucial time points for song development are similar to changes observed in dopamine studies and suggest Nts may be involved in the process of vocal learning. © 2018 Wiley Periodicals, Inc. Develop Neurobiol 78: 671-686, 2018.

To Become Senders, Songbirds Must be Receivers First

Courtship signals are attractive; in other words, receivers are motivated to approach courtship signals. Though the concept of a receiver is commonly associated in the literature with that of a mate seeker, young songbirds that are learning to sing by imitating conspecifics are also receivers. Juvenile songbirds are attracted to conspecific songs, which has been shown by juveniles working to hear song in operant chambers. The mechanisms explaining this attraction are poorly understood. Here, I review studies that hint at the mechanisms by which conspecific song becomes attractive. In at least some species, juveniles imitate individuals with which they have a strong social bond, such as the father. Such cases suggest that social reward plays a role in the process of song becoming attractive. In addition, experiments using birds reared in isolation from conspecific song have shown that juveniles imitate songs that have acoustic features that are typically found in conspecific song. Those studies suggest that such features are attractive to juveniles regardless of their social experience. The relative contributions of social reward and species-typical acoustic features to the attractiveness of a song can be determined using methods such as operant conditioning. For example, juvenile songbirds can be given control over the playback of songs that differ in a given attribute, such as acoustic similarity to the song of the father. The juveniles will frequently elicit playback of the songs that are attractive to them. Investigating the mechanisms that contribute to the attractiveness of conspecific song to learners will broaden our understanding of the evolution of song as a courtship signal, because the preferences of learners may ultimately determine what will be sung to potential mates.

Perineuronal nets and vocal plasticity in songbirds: A proposed mechanism to explain the difference between closed-ended and open-ended learning

Perineuronal nets (PNN) are aggregations of chondroitin sulfate proteoglycans surrounding the soma and proximal processes of neurons, mostly GABAergic interneurons expressing parvalbumin. They limit the plasticity of their afferent synaptic connections. In zebra finches PNN develop in an experience-dependent manner in the song control nuclei HVC and RA (nucleus robustus arcopallialis) when young birds crystallize their song. Because songbird species that are open-ended learners tend to recapitulate each year the different phases of song learning until their song crystallizes at the beginning of the breeding season, we tested whether seasonal changes in PNN expression would be found in the song control nuclei of a seasonally breeding species such as the European starling. Only minimal changes in PNN densities and total number of cells surrounded by PNN were detected. However, comparison of the density of PNN and of PNN surrounding parvalbumin-positive cells revealed that these structures are far less numerous in starlings that show extensive adult vocal plasticity, including learning of new songs throughout the year, than in the closed-ended learner zebra finches. Canaries that also display some vocal plasticity across season but were never formally shown to learn new songs in adulthood were intermediate in this respect. Together these data suggest that establishment of PNN around parvalbumin-positive neurons in song control nuclei has diverged during evolution to control the different learning capacities observed in songbird species. This differential expression of PNN in different songbird species could represent a key cellular mechanism mediating species variation between closed-ended and open-ended learning strategies. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 77: 975-994, 2017.

Where Is the Comparison in Comparative Cognition? Alternative Research Programs

Contemporary research on comparative cognition reflects two distinct programs. The purpose of the anthropocentric program is to discover whether nonhuman species process information in the same way as humans do. The ecological program analyzes ecologically significant aspects of cognition and compares them in closely and distantly related species. Research on memory for stored food in birds provides a detailed example of this latter program. Other examples include research on bird song learning and foraging and ecological analyses of human cognition.

Acquisition of Lateralized Predation Behavior Associated with Development of Mouth Asymmetry in a Lake Tanganyika Scale-Eating Cichlid Fish

The scale-eating cichlid Perissodus microlepis with asymmetric mouth is an attractive model of behavioral laterality: each adult tears off scales from prey fishes' left or right flanks according to the direction in which its mouth is skewed. To investigate the development of behavioral laterality and mouth asymmetry, we analyzed stomach contents and lower jaw-bone asymmetry of various-sized P. microlepis (22 ≤ SL<115 mm) sampled in Lake Tanganyika. The shapes of the pored scales found in each specimen's stomach indicated its attack side preference. Early-juvenile specimens (SL<45 mm) feeding mainly on zooplankton exhibited slight but significant mouth asymmetry. As the fish acquired scale-eating (45 mm ≤ SL), attack side preference was gradually strengthened, as was mouth asymmetry. Among size-matched individuals, those with more skewed mouths ate more scales. These findings show that behavioral laterality in scale-eating P. microlepis is established in association with development of mouth asymmetry which precedes the behavioral acquisition, and that this synergistic interaction between physical and behavioral literalities may contribute to efficient scale-eating.

Animal Models of Speech and Vocal Communication Deficits Associated With Psychiatric Disorders

Disruptions in speech, language, and vocal communication are hallmarks of several neuropsychiatric disorders, most notably autism spectrum disorders. Historically, the use of animal models to dissect molecular pathways and connect them to behavioral endophenotypes in cognitive disorders has proven to be an effective approach for developing and testing disease-relevant therapeutics. The unique aspects of human language compared with vocal behaviors in other animals make such an approach potentially more challenging. However, the study of vocal learning in species with analogous brain circuits to humans may provide entry points for understanding this human-specific phenotype and diseases. We review animal models of vocal learning and vocal communication and specifically link phenotypes of psychiatric disorders to relevant model systems. Evolutionary constraints in the organization of neural circuits and synaptic plasticity result in similarities in the brain mechanisms for vocal learning and vocal communication. Comparative approaches and careful consideration of the behavioral limitations among different animal models can provide critical avenues for dissecting the molecular pathways underlying cognitive disorders that disrupt speech, language, and vocal communication.

A framework to assess evolutionary responses to anthropogenic light and sound

Human activities have caused a near-ubiquitous and evolutionarily-unprecedented increase in environmental sound levels and artificial night lighting. These stimuli reorganize communities by interfering with species-specific perception of time-cues, habitat features, and auditory and visual signals. Rapid evolutionary changes could occur in response to light and noise, given their magnitude, geographical extent, and degree to which they represent unprecedented environmental conditions. We present a framework for investigating anthropogenic light and noise as agents of selection, and as drivers of other evolutionary processes, to influence a range of behavioral and physiological traits such as phenological characters and sensory and signaling systems. In this context, opportunities abound for understanding contemporary and rapid evolution in response to human-caused environmental change.

Reward associated with singing behavior correlates with opioid-related gene expression in the medial preoptic nucleus in male European starlings

Birdsong consists of species-specific learned vocal sequences that are used primarily to attract mates and to repel competitors during the breeding season. However, many birds continue to sing at times when vocal production has no immediate or obvious impact on conspecific behavior. The mechanisms that ensure that animals produce important behaviors in contexts in which the function of these behaviors is not immediate or obvious are not known. One possibility is that animals engage in such behaviors because they are associated with pleasure. Here we examined the hypothesis that male European starlings sing outside of the breeding season in part because the act of singing in this context is facilitated and/or maintained by opioid-mediated reward. We measured song-associated reward using a conditioned place preference (CPP) test in male starlings producing fall, non-breeding season-typical song. We used quantitative real time PCR to measure expression of the enkephalin opioid precursor preproenkephalin (PENK) and mu opioid receptors (MOR) in the medial preoptic nucleus (POM; a region in which opioids are implicated in both reward and starling fall song) and additionally the song control region HVC as a control. Starlings developed a strong preference for a place that had been paired previously with the act of producing fall-typical song, indicating that fall song production was associated with a positive affective state. Both PENK and MOR mRNA expression in the POM, but not HVC, correlated positively with both individual reward state (as reflected in CPP) and undirected singing behavior. These results suggest that singing induces opioid receptor and enkephalin expression in the POM and consequent reward, and/or that opioid release in the POM induced by individual or environmental factors (e.g., the presence of food, safety of a flock or the absence of predators) induces a positive affective state which then facilitates singing behavior.

Mapping the unconscious maintenance of a lost first language

Optimal periods during early development facilitate the formation of perceptual representations, laying the framework for future learning. A crucial question is whether such early representations are maintained in the brain over time without continued input. Using functional MRI, we show that internationally adopted (IA) children from China, exposed exclusively to French since adoption (mean age of adoption, 12.8 mo), maintained neural representations of their birth language despite functionally losing that language and having no conscious recollection of it. Their neural patterns during a Chinese lexical tone discrimination task matched those observed in Chinese/French bilinguals who have had continual exposure to Chinese since birth and differed from monolingual French speakers who had never been exposed to Chinese. They processed lexical tone as linguistically relevant, despite having no Chinese exposure for 12.6 y, on average, and no conscious recollection of that language. More specifically, IA participants recruited left superior temporal gyrus/planum temporale, matching the pattern observed in Chinese/French bilinguals. In contrast, French speakers who had never been exposed to Chinese did not recruit this region and instead activated right superior temporal gyrus. We show that neural representations are not overwritten and suggest a special status for language input obtained during the first year of development.

Control of vocal production in budgerigars (Melopsittacus undulatus): selective reinforcement, call differentiation, and stimulus control

Budgerigars were trained to make a specific call using a real-time automated call recognition system and food reward. Calls produced by the bird were followed by food only if they were similar enough to a template call. The selective reinforcement of a particular call type increased the similarity of the bird's call to the template and decreased overall call variation, including call duration. After the birds' performance reached asymptote (i.e. the calls became matched to the template with no further increase in similarity), a call differentiation procedure was introduced. This procedure consisted of both matching-to-template and non-matching-to-template trials. In order to receive food in non-matching-to-template trials, the birds had to produce a call that was sufficiently different from the template call. This procedure resulted in a `new' call emerging from the first template call which occurred gradually rather than abruptly. In the third procedure, called two-template matching training, the birds had to match their calls to the first template call (signaled by illuminating the left LED) and to the second template call (signaled by illuminating the right LED). The calls produced in both first and second template call trials were well controlled by the position of the LED. These results extend the effects of selective reinforcement, differential reinforcement, and stimulus control on response topographies to the domain of vocalizations in budgerigars.

The ontogeny of learned inhibition

Previous studies have examined the maturation of learning and memory abilities during early stages of development. By comparison, much less is known about the ontogeny of learning and memory during later stages of development, including adolescence. In Experiment 1, we tested the ability of adolescent and adult rats to learn a Pavlovian negative occasion setting task. This procedure involves learning to inhibit a behavioral response when signaled by a cue in the environment. During reinforced trials, a target stimulus (a tone) was presented and immediately followed by a food reward. On nonreinforced trials, a feature stimulus (a light) was presented 5 sec prior to the tone and indicated the absence of reward following presentation of the tone. Both adult and adolescent rats learned to discriminate between two different trial types and withhold responding when the light preceded the tone. However, adolescent rats required more sessions than adults to discriminate between reinforced and nonreinforced trials. The results of Experiment 2 revealed that adolescents could learn the task rules but were specifically impaired in expressing that learning in the form of withholding behavior on nonreinforced trials. In Experiment 3, we found that adolescents were also impaired in learning a different version of the task in which the light and tone were presented simultaneously during the nonreinforced trials. These findings add to existing literature by indicating that impairments in inhibitory behavior during adolescence do not reflect an inability to learn to inhibit a response, but instead reflect a specific deficit in expressing that learning.

Environmental and genetic control of brain and song structure in the zebra finch

Birdsong is a classic example of a learned trait with cultural inheritance, with selection acting on trait expression. To understand how song responds to selection, it is vital to determine the extent to which variation in song learning and neuroanatomy is attributable to genetic variation, environmental conditions, or their interactions. Using a partial cross fostering design with an experimental stressor, we quantified the heritability of song structure and key brain nuclei in the song control system of the zebra finch and the genotype-by-environment (G × E) interactions. Neuroanatomy and song structure both showed low levels of heritability and are unlikely to be under selection as indicators of genetic quality. HVC, in particular, was almost entirely under environmental control. G × E interaction was important for brain development and may provide a mechanism by which additive genetic variation is maintained, which in turn may promote sexual selection through female choice. Our study suggests that selection may act on the genes determining vocal learning, rather than directly on the underlying neuroanatomy, and emphasizes the fundamental importance of environmental conditions for vocal learning and neural development in songbirds.

Quantitative tools for examining the vocalizations of juvenile songbirds

The singing of juvenile songbirds is highly variable and not well stereotyped, a feature that makes it difficult to analyze with existing computational techniques. We present here a method suitable for analyzing such vocalizations, windowed spectral pattern recognition (WSPR). Rather than performing pairwise sample comparisons, WSPR measures the typicality of a sample against a large sample set. We also illustrate how WSPR can be used to perform a variety of tasks, such as sample classification, song ontogeny measurement, and song variability measurement. Finally, we present a novel measure, based on WSPR, for quantifying the apparent complexity of a bird's singing.

Directional cultural change by modification and replacement of memes

Evolutionary approaches to culture remain contentious. A source of contention is that cultural mutation may be substantial and, if it drives cultural change, then current evolutionary models are not adequate. But we lack studies quantifying the contribution of mutations to directional cultural change. We estimated the contribution of one type of cultural mutations--modification of memes--to directional cultural change using an amenable study system: learned birdsongs in a species that recently entered an urban habitat. Many songbirds have higher minimum song frequency in cities, to alleviate masking by low-frequency noise. We estimated that the input of meme modifications in an urban songbird population explains about half the extent of the population divergence in song frequency. This contribution of cultural mutations is large, but insufficient to explain the entire population divergence. The remaining divergence is due to selection of memes or creation of new memes. We conclude that the input of cultural mutations can be quantitatively important, unlike in genetic evolution, and that it operates together with other mechanisms of cultural evolution. For this and other traits, in which the input of cultural mutations might be important, quantitative studies of cultural mutation are necessary to calibrate realistic models of cultural evolution.

Cognitive training during infancy and adolescence accelerates adult associative learning: critical impact of age, stimulus contingency and training intensity

A growing body of evidence supports the hypothesis that juvenile cognitive training shapes neural networks and behavior, and thereby determines the adult's capacity for learning and memory. In particular, we have shown that infant rats, even though they do not develop an active avoidance strategy in a two-way active avoidance task, show as adults accelerated learning in the same learning task. This indicates that a memory trace was formed in the infant rats, which most likely is recruited during adult training. To identify the learning conditions, which are essential prerequisites to form this memory trace in infancy or adolescence, we investigated the critical impact of: (i) age, (ii) CS-UCS contingency, and (iii) pre-training intensity on this facilitating effect. We observed: (i) an age-dependent improvement of avoidance learning, (ii) that the beneficial impact of infant or adolescent pre-training on adult learning increases with the age at pre-training, (iii) that CS-UCS contingency during infant pre-training was most efficient to accelerate adult learning, (iv) that pre-training intensity (i.e. number of pre-training trials) was positively correlated with the pre-training induced acceleration of adult learning, and (v) that infant rats, compared to adolescent rats, need a higher training intensity to show learning improvement as adults. These results indicate that infant rats develop a goal-oriented escape strategy, which during adult training is replaced by an avoidance strategy, facilitated by the recruitment of the CS-UCS association, which has been learned during infant training. Based on these results the future challenge will be to identify the specific contribution of prefronto-limbic circuits in infant and adult learning in relation to their functional maturation.

Neurobiology of song learning

Birdsong is a culturally transmitted behavior that depends on a juvenile songbird's ability to imitate the song of an adult tutor. Neurobiological studies of birdsong can reveal how a complex form of imitative learning, which bears strong parallels to human speech learning, can be understood at the level of underlying circuit, cellular, and synaptic mechanisms. This review focuses on recent studies that illuminate the neurobiological mechanisms for singing and song learning.

Molecular cloning and characterization of the germline-restricted chromosome sequence in the zebra finch

The zebra finch (Taeniopygia guttata) germline-restricted chromosome (GRC) is the largest chromosome and has a unique system of transmission in germ cells. In the male, the GRC exists as a single heterochromatic chromosome in the germline and is eliminated from nuclei in late spermatogenesis. In the female, the GRC is bivalent and euchromatic and experiences recombination. These characteristics suggest a female-specific or female-beneficial function of the GRC. To shed light on the function of GRC, we cloned a portion of the GRC using random amplified polymorphic DNA-polymerase chain reaction and analyzed it using molecular genetic and cytogenetic methods. The GRC clone hybridized strongly to testis but not blood DNA in genomic Southern blots. In fluorescent in situ hybridization analysis on meiotic chromosomes from synaptonemal complex spreads, the probe showed hybridization across a large area of the GRC, suggesting that it contains repetitive sequences. We isolated a sequence homologous to the GRC from zebra finch chromosome 3 and a region of chicken chromosome 1 that is homologous to zebra finch chromosome 3; the phylogenetic analysis of these three sequences suggested that the GRC sequence and the zebra finch chromosome 3 sequence are most closely related. Thus, the GRC sequences likely originated from autosomal DNA and have evolved after the galliform-passeriform split. The present study provides a foundation for further study of the intriguing GRC.

Chromosomal polymorphism and comparative painting analysis in the zebra finch

The zebra finch (Taeniopygia guttata) is often studied because of its interesting behaviour and neurobiology. Genetic information on this species has been lacking, making analysis of informative mutants difficult. Here we report on an improved cytological method for preparation of metaphase chromosomes suitable for fluorescent in situ hybridization of adult birds. We found that individual chicken chromosome paints usually hybridized to single zebra finch chromosomes, indicating only minor chromosomal rearrangements since the evolutionary divergence of these two species, and suggesting that the genomic location of chicken genes will predict the location of zebra finch orthologues. Chicken chromosome 1 appears to have split into two macrochromosomes in zebra finches, and chicken chromosome 4 paint hybridizes to a zebra finch macrochromosome and a microchromosome. This pattern was confirmed by mapping the androgen receptor (AR), which is located on chicken chromosome 4 but on a zebra finch microchromosome. We detected a telocentric/submetacentric polymorphism of chromosome 6 in our colony of zebra finches, and found that the polymorphism was inherited in a Mendelian pattern.

In search of the song template

The auditory template theory-the conversion of memorized song to produced song using feedback as an error-correction mechanism-is central to neurobiological studies of birdsong learning. The essence of the theory is the construction of a complex sound replica based on a set of both genetic and environmental instructions. These premises, as yet unchallenged, have stimulated much research on the process of vocal imitation. Two somewhat distinct, but closely related streams of research have emerged. One seeks to determine the neural mechanisms that underlie the formation, storage, and retrieval of vocal memories as a consequence of experience during a sensitive phase-the template concept in its purest form. The other aims at establishing an explanatory basis for genetically based species differences in auditory responsiveness; here, the prime focus is on innately specified templates that guide learning preferences in young, naïve birds. The chapter begins with an historical overview of conceptual issues. Then recent progress in the attempt to characterize template properties is reviewed, focusing on selected studies of sparrows, nightingales, and zebra finches. The chapter concludes with a discussion of research strategy and tactics, including suggestions for criteria that must be met in identifying neural substrates for template specification and localization. The chapter is intended to provide a conceptual framework for further progress in this critical area.

Genes, interactions, and the development of behavior

Explaining how genes influence behavior is important to many branches of psychology, including development, behavior genetics, and evolutionary psychology. Presented here is a developmental model linking the immediate consequence of gene activity (transcription of messenger RNA molecules from DNA sequences) to behavior through multiple molecular, cellular, and physiological levels. The model provides a level of detail appropriate to theories of behavioral development that recognizes the molecular level of gene action, dispensing with the metaphorical use of such terms as blueprints, plans, or constraints that has obscured much previous discussion. Special attention is paid to the possible role of immediate-early genes in initiating developmental responses to experience, adding specificity to the claim that neither genes nor experience act alone to shape development.

Re-expression of songs deleted during vocal development in white-crowned sparrows, Zonotrichia leucophrys

White-crowned sparrows learn and produce multiple song types as juveniles, but most individuals stop singing all except one by the end of the first singing season. This single song type is generally maintained throughout adulthood. We demonstrate that, at the start of the second and subsequent singing seasons, this species can recall songs that had been deleted during the first singing season. The re-expression of song occurred in both the oriantha and the gambelii subspecies. Although all our males recrystallized the original song in the second year, our results indicate a mechanism for seasonal song change without new song memorization. The traditional dichotomy of closed-ended versus open-ended learning is inadequate for birds that learn early in life but can change their song output seasonally. We suggest that species can exhibit a closed sensitive period for song memorization and first production, with the ability to recall deleted songs later in life. This type of learning, selective attrition followed by subsequent re-expression, may be used by some species currently considered open-ended learners. Copyright 2000 The Association for the Study of Animal Behaviour.

Social influences during song development in the song sparrow: a laboratory experiment simulating field conditions

Oscine songbirds are exposed to many more songs than they keep for their final song repertoire and little is known about how a bird selects the particular song(s) to sing as an adult. We simulated in the laboratory the key variables of the natural song learning environment and examined the song selection process in nine hand-reared male song sparrows, Melospiza melodia, a species in which males sing 5-11 song types. During their second and third months (their presumed sensitive period), subjects were rotated equally among four live adult male tutors that had been neighbours in the field. Tutors were housed in individual aviary 'territories' in four corners of the roof of a building; subjects could see only one tutor at a time, but they could hear the others at a short distance. Later in their first year (months 5-12), half the subjects were again rotated among all four tutors and the other half were randomly stationed next to just one tutor. Results from this experiment confirm and extend the findings from our two previous field studies of song learning in this species. Young males in this experiment (1) learned whole song types, (2) learned songs from multiple tutors, (3) preferentially learned songs that were shared among their tutors, (4) learned songs that other young males in their group also chose, and (5) learned more songs from the tutor they were stationed next to during the later stage (stationary subjects). These last two results support the late influence hypothesis that interactions after a bird's sensitive period affect song repertoire development. Copyright 2000 The Association for the Study of Animal Behaviour.

Does learning affect the structure of vocalizations in chimpanzees?

We recorded 'pant-hoot' vocalizations from male chimpanzees, Pan troglodytes, housed in two captive facilities in the U.S.A., Lion Country Safari and North Carolina Zoological Park. Acoustic analysis revealed significant differences between the two groups in the temporal patterning of the calls. Because the captive males within each group are from diverse origins, within-group similarity in pant-hoot structure could not have resulted from genetic similarity of the callers. In addition, there were no obvious differences in housing conditions that could have caused the between-group differences. Instead, the results suggest that the calls in each group converged in structure as a consequence of vocal learning. Within-group variation in call structure of the captive groups was similar to that found in a group of wild Ugandan chimpanzees (Kanyawara study group, Kibale National Park), suggesting the presence of species-specific constraints on this call within which different populations can converge on local variants. In addition, an acoustically novel pant-hoot variant that was introduced by one male to the Lion County Safari colony spread to five other males in the same colony. This suggests that chimpanzees may also be able to modify the frequency parameters of their calls through learning. Copyright 1999 The Association for the Study of Animal Behaviour.

Ecological influences on vocal development in the white-crowned sparrow

Gambel's white-crowned sparrow, Zonotrichia leucophrys gambelii, is a long-distance migrant that, in contrast to other subspecies of white-crowned sparrow, does not form vocal dialects. I studied the process of vocal development in the field and laboratory to determine how it differed from the process in three other subspecies previously studied. Four common song types existed in a random spatial pattern in my 2.6-km(2)study area. Of 106 males studied in 2 years, all arrived at the beginning of the breeding season singing their adult repertoire and no male changed his song during the season. In the laboratory, hand-reared males overproduced as much as other migratory subspecies of white-crowned sparrow. They learned their songs during the shortest sensitive phase of any white-crowned sparrow yet studied. In contrast to other subspecies that form vocal dialects, male gambelii chose their final adult song at random from their overproduced repertoire. I suggest the absence of vocal dialects in Gambel's sparrow results from the short, delayed breeding season on their sub-Arctic breeding grounds. The short breeding season has favoured a narrow sensitive phase in hatching-year birds, and prevents the extended vocal interactions among adults that lead to vocal dialects in populations breeding at temperate latitudes. Copyright 1999 The Association for the Study of Animal Behaviour.

Anterior forebrain pathway is needed for stable song expression in adult male white-crowned sparrows (Zonotrichia leucophrys)

The anterior forebrain pathway of the avian song system is involved in juvenile song learning, but its function in adult song behavior is not known. This report uses lesions to study the role of a particular forebrain nucleus, IMAN, in the seasonal regeneration of song in adult white-crowned sparrows (Zonotrichia leucophrys oriantha). White-crowned sparrows, even when acoustically isolated as juveniles, crystallize a single song which they maintain throughout adulthood. The lateral portion of the magnocellular nucleus of the anterior neostriatum (1MAN) was lesioned bilaterally in adult males maintained on short days (8 h of light). Daylength was increased to 16 h following the surgeries, and all birds were recorded in the post-lesion singing season. Lesioned birds showed a large decrease in song note frequency following the lesions, significantly larger than did intact, age-matched controls. Further changes were seen in the post-lesion songs of seven of 11 successfully lesioned males. These changes included variability in song pattern, loss of frequency control and addition of new notes, some of which had been practiced during juvenile song development. These changes seemed especially large in birds that had either been acoustically isolated or had not fully copied a tape-tutor song during juvenile song development. These results are the first to indicate that the motor memories for song elements that had been practiced and discarded early in life are retained, and they suggest that 1MAN affects seasonal song expression by selectively reinforcing a particular song pattern.

Cultural variation in savannah sparrow, Passerculus sandwichensis, songs: an analysis using the meme concept

I used the meme concept to investigate patterns of cultural variation among the songs of eight, geographically distinct populations of savannah sparrows. Memes composed of only one syllable were geographically widespread and randomly distributed among populations, but memes of two-, three- and four-syllables became progressively more restricted in their geographical distribution. Thus, the populations were memetically more similar with respect to one-syllable memes and more divergent with respect to larger memes. These results suggest that differences in memetic mutation rates and susceptibility to loss by memetic drift could be sufficient to create the observed pattern of greater divergence among populations for large memes. Copyright 1998 The Association for the Study of Animal Behaviour.

Ontogeny of the conditioned eyeblink response in rats: acquisition or expression?

Eyeblink conditioning depends critically on an identified brainstem-cerebellar circuit and is modulated under some circumstances by the hippocampus, amygdala, and other forebrain regions. Developmental studies of eyeblink conditioning could help elucidate questions concerning the behavioral expression of plasticity within these brain circuits and regions, and of their functional interactions, as they unfold during ontogeny. Recently, this laboratory has shown that conditioning of the eyeblink reflex develops dramatically between Postnatal Days (PND) 17 and PND 24 in the rat. The present study asked whether the developmental emergence of the eyeblink conditioned response (CR) occurs gradually or abruptly over this age range, and whether it reflects developmental changes in acquisition or expression of the learned eyeblink reflex. In Experiment 1, rat pups received two consecutive days of training beginning on PND 17, 20, or 24. Conditioned responses occurred at low levels on PND 17-18, intermediate levels on PND 20-21, and high levels on PND 24-25. In Experiment 2, 17-day-old rats received 2 days of training, 72 h apart, so that effects of training on PND 17 could be examined at an age, PND 20, when expression of the eyeblink CR was clearly possible. On PND 20, rat pups that had received paired training on PND 17 showed significantly faster conditioning than controls that had received unpaired training or no training on PND 17. These findings suggest that neural plasticity underlying associative learning developmentally precedes its overt expression in behavior. Hypotheses concerning the nature and locus of this learning are discussed.

Phrase structure of wild chimpanzee pant hoots: Patterns of production and interpopulation variability

Recordings and behavioral observations of wild chimpanzees were made over a 2-year period in the Kibale National Park, Uganda (Kanyawara and Ngogo communities) to investigate patterns of acoustic variability in long-distance calls. The phrase structures of pant hoots, the species-typical loud call given predominantly by adult males, were analyzed. Analysis revealed that the build-up phrase was frequently absent from the pant hoots of Kibale chimpanzees. By contrast, analysis of published data on Gombe and Mahale chimpanzees (Tanzania) indicated that these animals typically included the build-up in their calls. These results were interpreted as evidence for phrase-level differences between populations in the acoustic morphology of this compound call. Data on age and sex differences in the context of production of pant hoots were analyzed, and their relevance to the possibility that aspects of pant hoot acoustic morphology are learned is discussed. Adult males initiated pant hoots more than subadult males, and adult males joined other pant hooting individuals with pant hoots more than subadult males did. It is suggested that younger males may pant hoot with specific adult males preferentially and that this may affect the development of their pant hoot acoustic morphologies. A peculiar pant hoot variant previously reported from Gombe, the whimper hoot, is described from Kibale. The production of this call by low-ranking individuals suggests that there are social constraints on pant hooting in the chimpanzee community. Ideas concerning the effect of social relationships on interpopulation variability in vocal signals are briefly discussed. © 1996 Wiley-Liss, Inc.

White-throated sparrow morphs that differ in song production rate also differ in the anatomy of some song-related brain areas

White-throated sparrows are unusual among songbirds in that they occur in two color morphs, white-striped and tan-striped, determined by a chromosomal inversion and maintained by negative assortative mating. These differ in several reproductive behaviors, including amount of singing: white-striped males sing frequently, tan-striped females never sing, and tan-striped males and white-striped females sing an intermediate amount. The present study measures the volumes of several nuclei in the avian song system and relates these to color morph and to sex. We find that robustus archistristalis and the tracheosyringeal part of the hypoglossal nucleus, nuclei closely involved in song production, are larger in white-striped than in tan-striped birds. We also find morph differences for nuclei in the rostral division of the song system, nuclei believed to be less directly involved in song production. We find sex differences throughout the song system as has been reported in other songbirds. Relationships between structure and function in the song system are discussed.

Relations between song repertoire size and the volume of brain nuclei related to song: comparative evolutionary analyses amongst oscine birds

Song and brain structure are compared amongst 41 species of oscine birds by using the method of independent evolutionary contrasts. We find a significant correlation between the relative volume of the song control centre, the high vocal centre (HVC), and the number of song types typically found in the repertoire. Relative HVC volume is not correlated with the number of different syllable types per song bout. The relative volume of a second song nucleus, area X, is not significantly correlated with either measure. Relative HVC volume is uncorrelated with relative volume of the hippocampus, a brain area involved in other forms of memory. This is the first evidence for repeated independent evolution of an association between complexity of learned song and the relative volume of one of the song control nuclei though to be involved in song learning.