Zebra Finch Song Research Articles

Social and auditory experience shapes forebrain responsiveness in zebra finches before the sensitive period of vocal learning.

Early-life experiences with signals used in communication are instrumental in shaping an animal's social interactions. In songbirds, which use vocalizations for guiding social interactions and mate choice, recent studies show that sensory effects on development occur earlier than previously expected, even in embryos and nestlings. Here, we explore the neural dynamics underlying experience-dependent song categorization in young birds prior to the traditionally studied sensitive period of vocal learning that begins around 3 weeks post-hatch. We raised zebra finches either with their biological parents, cross-fostered by Bengalese finches beginning at embryonic day 9, or by only the non-singing mother from 2 days post-hatch. Then, 1-5 days after fledging, we conducted behavioral experiments and extracellular recordings in the auditory forebrain to test responses to zebra finch and Bengalese finch songs. Auditory forebrain neurons in cross-fostered and isolate birds showed increases in firing rate and decreases in responsiveness and selectivity. In cross-fostered birds, decreases in responsiveness and selectivity relative to white noise were specific to conspecific song stimuli, which paralleled behavioral attentiveness to conspecific songs in those same birds. This study shows that auditory and social experience can already impact song 'type' processing in the brains of nestlings, and that brain changes at this age can portend the effects of natal experience in adults.

The ecology of zebra finch song and its implications for vocal communication in multi-level societies.

Acoustic signalling is crucial in affecting movements and in social interactions. In species with dynamic social structures, such as multi-level societies, acoustic signals can provide a key mechanism allowing individuals to identify and find or avoid each other and to exchange information. Yet, if the spacing between individuals regularly exceeds the maximum signalling range, the relation between movements and signals becomes more complex. As the best-studied songbird in captivity, the zebra finch (Taeniopygia castanotis) is a species with individually distinct songs that are audible over just a few metres and a widely ranging dynamic multi-level social organization in the wild, raising questions on the actual role of its song in social cohesion and coordination. Here, we provide an overview of birdsong in social organizations (networks) and use the ecology of the zebra finch and male song to discuss how singing can facilitate social cohesion and coordination in species where the signal range is very short. We raise the question of the extent to which zebra finches are a representative species to understand the function of song in communication, and we broaden current views on the function of birdsong and its individual signature. This article is part of the theme issue 'The power of sound: unravelling how acoustic communication shapes group dynamics'.

Zebra finch song parameters are affected by the breeding status of the male, but not temperature variability

Bird song is a crucial feature for mate choice and reproduction. Song can potentially communicate information related to the quality of the mate, through song complexity, structure or finer changes in syllable characteristics. It has been shown in zebra finches that those characteristics can be affected by various factors including motivation, hormone levels or extreme temperature. However, although the literature on zebra finch song is substantial, some factors have been neglected. In this paper, we recorded male zebra finches in two breeding contexts (before and after pairing) and in two ambient temperature conditions (stable and variable) to see how those factors could influence song production. We found strong differences between the two breeding contexts: compared to their song before pairing, males that were paired had lower song rate, syllable consistency, frequency and entropy, while surprisingly the amplitude of their syllables increased. Temperature variability had an impact on the extent of these differences, but did not directly affect the song parameters that we measured. Our results describe for the first time how breeding status and temperature variability can affect zebra finch song, and give some new insights into the subtleties of the acoustic communication of this model species.

Tracing the development of learned song preferences in the female zebra finch brain with functional magnetic resonance imaging.

In sexually dimorphic zebra finches (Taeniopygia guttata), only males learn to sing their father's song, whereas females learn to recognize the songs of their father or mate but cannot sing themselves. Memory of learned songs is behaviorally expressed in females by preferring familiar songs over unfamiliar ones. Auditory association regions such as the caudomedial mesopallium (CMM; or caudal mesopallium) have been shown to be key nodes in a network that supports preferences for learned songs in adult females. However, much less is known about how song preferences develop during the sensitive period of learning in juvenile female zebra finches. In this study, we used blood-oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to trace the development of a memory-based preference for the father's song in female zebra finches. Using BOLD fMRI, we found that only in adult female zebra finches with a preference for learned song over novel conspecific song, neural selectivity for the father's song was localized in the thalamus (dorsolateral nucleus of the medial thalamus; part of the anterior forebrain pathway, AFP) and in CMM. These brain regions also showed a selective response in juvenile female zebra finches, although activation was less prominent. These data reveal that neural responses in CMM, and perhaps also in the AFP, are shaped during development to support behavioral preferences for learned songs.

Physiological constraints and cognitive chunking: Sequence organization in the songs of zebra finches (Taeniopygia guttata).

Learned bird songs often have a hierarchical organization. In the case of zebra finches, each bird's song is made up of a string of notes delivered in a stereotyped sequence to form a "motif," and motifs are repeated to form a song bout. During song learning, young males copy "chunks" of two or more consecutive notes from their tutors' songs. These chunks are represented as distinct units within memory (during learning) and within motor systems (during song production). During song performance, motifs may deviate from the learned sequence by stopping short, starting late, or by skipping, inserting, or repeating notes. We measured acoustic and temporal variables related to the respiratory and vocal physiology of song production and asked how they related to deviations from each bird's "canonical" sequence. The best predictor of deviations from that sequence was the duration of the silent interval between notes, when inspiration normally occurs. Deviations from the canonical motif occurred less often after higher-pitched notes, perhaps because a high-low sequence forms a prosodic unit. Premature stops often followed louder and longer notes, suggesting that respiratory and muscular physiology influence the location of such stops. Boundaries between the learned chunks of a male's motif predicted where and how often noncanonical starts occurred. Physiological and cognitive elements also interacted to define the segmentation of zebra finch song sequences. Long silent intervals between notes were associated both with physiology (inspirations) and with the cognitive boundaries of learned chunks-and hence with deviations from the canonical motif. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Estimating Mutual Information for Spike Trains: A Bird Song Example.

Zebra finches are a model animal used in the study of audition. They are adept at recognizing zebra finch songs, and the neural pathway involved in song recognition is well studied. Here, this example is used to illustrate the estimation of mutual information between stimuli and responses using a Kozachenko-Leonenko estimator. The challenge in calculating mutual information for spike trains is that there are no obvious coordinates for the data. The Kozachenko-Leonenko estimator does not require coordinates; it relies only on the distance between data points. In the case of bird songs, estimating the mutual information demonstrates that the information content of spiking does not diminish as the song progresses.

Uncoordinated sleep replay across hemispheres in the zebra finch

Bilaterally organized brain regions are often simultaneously active in both humans1,2,3 and animal models,4,5,6,7,8,9 but the extent to which the temporal progression of internally generated dynamics is coordinated across hemispheres and how this coordination changes with brain state remain poorly understood. To address these issues, we investigated the zebra finch courtship song (duration: 0.5-1.0 s), a highly stereotyped complex behavior10,11 produced by a set of bilaterally organized nuclei.12,13,14 Unilateral lesions to these structures can eliminate or degrade singing,13,15,16,17 indicating that both hemispheres are required for song production.18 Additionally, previous work demonstrated broadly coherent and symmetric bilateral premotor signals during song.9 To precisely track the temporal evolution of activity in each hemisphere, we recorded bilaterally in the song production pathway. We targeted the robust nucleus of the arcopallium (RA) in the zebra finch, where population activity reflects the moment-to-moment progression of the courtship song during awake vocalizations19,20,21,22,23,24 and sleep, where song-related network dynamics reemerge in "replay" events.24,25 We found that activity in the left and right RA is synchronized within a fraction of a millisecond throughout song. In stark contrast, the two hemispheres displayed largely independent replay activity during sleep, despite shared interhemispheric arousal levels. These findings demonstrate that the degree of bilateral coordination in the zebra finch song system is dynamically modulated by behavioral state.

Cannabidiol inhibits neuroinflammatory responses and circuit-associated synaptic loss following damage to a songbird vocal pre-motor cortical-like region

The non-euphorigenic phytocannabinoid cannabidiol (CBD) has been used successfully to treat childhood-onset epilepsies. These conditions are associated with developmental delays that often include vocal learning. Zebra finch song, like language, is a complex behavior learned during a sensitive period of development. Song quality is maintained through continuous sensorimotor refinement involving circuits that control learning and production. Within the vocal motor circuit, HVC is a cortical-like region that when partially lesioned temporarily disrupts song structure. We previously found CBD (10 mg/kg/day) improves post-lesion vocal recovery. The present studies were done to begin to understand mechanisms possibly responsible for CBD vocal protection. We found CBD markedly reduced expression of inflammatory mediators and oxidative stress markers. These effects were associated with regionally-reduced expression of the microglial marker TMEM119. As microglia are key regulators of synaptic reorganization, we measured synapse densities, finding significant lesion-induced circuit-wide decreases that were largely reversed by CBD. Synaptic protection was accompanied by NRF2 activation and BDNF/ARC/ARG3.1/MSK1 expression implicating mechanisms important to song circuit node mitigation of oxidative stress and promotion of synaptic homeostasis. Our findings demonstrate that CBD promotes an array of neuroprotective processes consistent with modulation of multiple cell signaling systems, and suggest these mechanisms are important to post-lesion recovery of a complex learned behavior.

Divergent projections from locus coeruleus to the corticobasal ganglia system and ventral tegmental area of the adult male zebra finch.

The locus coeruleus (LC) is a small noradrenergic brainstem nucleus that plays a central role in regulating arousal, attention, and performance. In the mammalian brain, individual LC neurons make divergent axonal projections to different brain regions, which are distinguished in part by which noradrenaline (NA) receptor subtypes they express. Here, we sought to determine whether similar organizational features characterize LC projections to corticobasal ganglia (CBG) circuitry in the zebra finch song system, with a focus on the basal ganglia nucleus Area X, the thalamic nucleus DLM, as well as the cortical nuclei HVC, LMAN, and RA. Single and dual retrograde tracer injections reveal that single LC-NA neurons make divergent projections to LMAN and Area X, as well as to the dopaminergic VTA/SNc complex that innervates this CBG circuit. Moreover, in situ hybridization revealed that differential expression of mRNA encoding α2A and α2C adrenoreceptors distinguishes LC-recipient CBG song nuclei. Therefore, LC-NA signaling in the zebra finch CBG circuit employs a similar strategy as in mammals, which could allow a relatively small number of LC neurons to exert widespread yet distinct effects across multiple brain regions.

Thalamus drives vocal onsets in the zebra finch courtship song.

While motor cortical circuits contain information related to specific movement parameters1, long-range inputs also have a critical role in action execution2,3. Thalamic projections can shape premotor activity2-6 and have been suggested7 to mediate the selection of short, stereotyped actions comprising more complex behaviours8. However, the mechanisms by which thalamus interacts with motor cortical circuits to execute such movement sequences remain unknown. Here we find that thalamic drive engages a specific subpopulation of premotor neurons within the zebra finch song nucleus HVC (proper name) and that these inputs are critical for the progression between vocal motor elements (that is, 'syllables'). In vivo two-photon imaging of thalamic axons in HVC showed robust song-related activity, and online perturbations of thalamic function caused song to be truncated at syllable boundaries. We used thalamic stimulation to identify a sparse set of thalamically driven neurons within HVC, representing ~15% of the premotor neurons within that network. Unexpectedly, this population of putative thalamorecipient neurons is robustly active immediately preceding syllable onset, leading to the possibility that thalamic input can initiate individual song components through selectively targeting these 'starter cells'. Our findings highlight the motor thalamus as a director of cortical dynamics in the context of an ethologically relevant behavioural sequence.

Supplemental Material for Physiological Constraints and Cognitive Chunking: Sequence Organization in the Songs of Zebra Finches (Taeniopygia guttata)

Supplemental Material for Physiological Constraints and Cognitive Chunking: Sequence Organization in the Songs of Zebra Finches (Taeniopygia guttata)

The social role of song in wild zebra finches

Male songbirds sing to establish territories and to attract mates.1,2 However, increasing reports of singing in non-reproductive contexts3 and by females4,5 show that song use is more diverse than previously considered. Therefore, alternative functions of song, such as social cohesion3 and synchronization of breeding, by and large, were overlooked even in such well-studied species such as the zebra finch (Taeniopygia guttata). In these social songbirds, only the males sing, and pairs breed synchronously in loose colonies,6,7 following aseasonal rain events in their arid habitat.8,9 As males are not territorial, and pairs form long-term monogamous bonds early in life, conventional theory predicts that zebra finches should not sing much at all; however, they do and their song is the focus of hundreds of lab-based studies.10,11,12,13,14,15,16,17,18,19,20,21,22 We hypothesize that zebra finch song functions to maintain social cohesion and to synchronize breeding. Here, we test this idea using data from 5 years of field studies, including observational transects, focal and year-round audio recordings, and a large-scale playback experiment. We show that zebra finches frequently sing while in groups, that breeding status influences song output at the nest and at aggregations, that they sing year round, and that they predominantly sing when with their partner, suggesting that the song remains important after pair formation. Our playback reveals that song actively features in social aggregations as it attracts conspecifics. Together, these results demonstrate that birdsong has important functions beyond territoriality and mate choice, illustrating its importance in coordination and cohesion of social units within larger societies.

Differences in dopamine and opioid receptor ratios in the nucleus accumbens relate to physical contact and undirected song in pair-bonded zebra finches.

Long-term social bonds are critical for survival and reproductive success in many species. Although courtship and pair-bond formation are relatively well studied, much less is known about the neural regulation of behaviors that occur after pair bonding that reinforce the bond and contribute to reproductive success. Dopamine and opioids in the nucleus accumbens (NAc) alter motivational state and reward by binding to receptor subtypes that engage distinct and opposing second messenger systems, and there is evidence that receptor ratios may influence social behavior. We used quantitative real-time PCR to explore relationships between messenger RNA ratios for dopamine D1 and D2 receptors (D1:D2) and mu and kappa opioid receptors (MOR:KOR) in NAc and behaviors implicated in reproductive investment and pair-bond maintenance in established male-female zebra finch pairs. In males, D1:D2 expression in NAc related negatively, whereas MOR:KOR related positively, to undirected song production. D1:D2 receptors also related positively to physical contact with a female. For females, D1:D2 expression was lower in females exposed to high compared to low rates of the partner's undirected song, and MOR:KOR expression in females related positively to undirected song exposure and allopreening. Analyses of single genes did not yield the same results. These findings suggest that the ratio of D1 to D2 and MOR to KOR receptor signaling in NAc causes differences in behavior or that behavior (or the partner's behavior) causes receptor ratio changes to modulate behaviors that maintain pair bonds and promote reproductive investment. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Resurgent Na+ currents promote ultrafast spiking in projection neurons that drive fine motor control

The underlying mechanisms that promote precise spiking in upper motor neurons controlling fine motor skills are not well understood. Here we report that projection neurons in the adult zebra finch song nucleus RA display robust high-frequency firing, ultra-narrow spike waveforms, superfast Na+ current inactivation kinetics, and large resurgent Na+ currents (INaR). These properties of songbird pallial motor neurons closely resemble those of specialized large pyramidal neurons in mammalian primary motor cortex. They emerge during the early phases of song development in males, but not females, coinciding with a complete switch of Na+ channel subunit expression from Navβ3 to Navβ4. Dynamic clamping and dialysis of Navβ4’s C-terminal peptide into juvenile RA neurons provide evidence that Navβ4, and its associated INaR, promote neuronal excitability. We thus propose that INaR modulates the excitability of upper motor neurons that are required for the execution of fine motor skills.

Supplemental Material for Differences in Dopamine and Opioid Receptor Ratios in the Nucleus Accumbens Relate to Physical Contact and Undirected Song in Pair-Bonded Zebra Finches

Supplemental Material for Differences in Dopamine and Opioid Receptor Ratios in the Nucleus Accumbens Relate to Physical Contact and Undirected Song in Pair-Bonded Zebra Finches

Zebra finch song is a very short-range signal in the wild: evidence from an integrated approach.

Birdsong is typically seen as a long-range signal functioning in mate attraction and territory defense. Among birds, the zebra finch is the prime model organism in bioacoustics, yet almost exclusively studied in the lab. In the wild, however, zebra finch song differs strikingly from songbirds commonly studied in the wild as zebra finch males sing most after mating and in the absence of territoriality. Using data from the wild, we here provide an ecological context for a wealth of laboratory studies. By integrating calibrated sound recordings, sound transmission experiments and social ecology of zebra finches in the wild with insights from hearing physiology we show that wild zebra finch song is a very short-range signal with an audible range of about nine meters and that even the louder distance calls do not carry much farther (up to about fourteen meters). These integrated findings provide an ecological context for the interpretation of laboratory studies of this species and indicate that the vocal communication distance of the main laboratory species for avian acoustics contrasts strikingly with songbirds that use their song as a long-range advertisement signal.

Vocal learning in songbirds: the role of syllable order in song recognition.

Songbird vocal learning has interesting behavioural and neural parallels with speech acquisition in human infants. Zebra finch males sing one unique song that they imitate from conspecific males, and both sexes learn to recognize their father's song. Although males copy the stereotyped syllable sequence of their father's song, the role of sequential information in recognition remains unclear. Here, we investigated father's song recognition after changing the serial order of syllables (switching the middle syllables, first and last syllables, or playing all syllables in inverse order). Behavioural approach and call responses of adult male and female zebra finches to their father's versus unfamiliar songs in playback tests demonstrated significant recognition of father's song with all syllable-order manipulations. We then measured behavioural responses to normal versus inversed-order father's song. In line with our first results, the subjects did not differentiate between the two. Interestingly, when males' strength of song learning was taken into account, we found a significant correlation between song imitation scores and the approach responses to the father's song. These findings suggest that syllable sequence is not essential for recognition of father's song in zebra finches, but that it does affect responsiveness of males in proportion to the strength of vocal learning.This article is part of the theme issue ‘Vocal learning in animals and humans’.

The Direction of response selectivity between conspecific and heterospecific auditory stimuli varies with response metric

Species recognition is an essential behavioral outcome of social discrimination, flocking, mobbing, mating, and/or parental care. In songbirds, auditory species recognition cues are processed through specialized forebrain circuits dedicated to acoustic discrimination. Here we addressed the direction of behavioral and neural metrics of zebra finches’ (Taeniopygia guttata) responses to acoustic cues of unfamiliar conspecifics vs. heterospecifics. Behaviorally, vocal response rates were greater for conspecific male zebra finch songs over heterospecific Pin-tailed Whydah (Vidua macroura) songs, which paralleled greater multiunit spike rates in the auditory forebrain in response to the same type of conspecific over heterospecific auditory stimuli. In contrast, forebrain activation levels were reversed to species-specific song playbacks during two functional magnetic resonance imaging experiments: we detected consistently greater responses to whydah songs over finch songs and did so independently of whether subjects had been co-housed or not with heterospecifics. These results imply that the directionality of behavioral and neural response selectivity metrics are not always consistent and appear to be experience-independent in this set of stimulus-and-subject experimental paradigms.

Basal ganglia: Bursting with song

The songs of mature zebra finches are notoriously repetitious, or 'crystallized'. Despite this stability, new work reveals that chronic pharmacologically driven bursting of cortical inputs to the basal ganglia can drive cumulative and lasting changes to multiple vocal features, including phenomena reminiscent of human stuttering.

Balanced imitation sustains song culture in zebra finches

Songbirds acquire songs by imitation, as humans do speech. Although imitation should drive convergence within a group and divergence through drift between groups, zebra finch songs sustain high diversity within a colony, but mild variation across colonies. We investigated this phenomenon by analyzing vocal learning statistics in 160 tutor-pupil pairs from a large breeding colony. Song imitation is persistently accurate in some families, but poor in others. This is not attributed to genetic differences, as fostered pupils copied their tutors’ songs as accurately or poorly as biological pupils. Rather, pupils of tutors with low song diversity make more improvisations compared to pupils of tutors with high song diversity. We suggest that a frequency dependent balanced imitation prevents extinction of rare song elements and overabundance of common ones, promoting repertoire diversity within groups, while constraining drift across groups, which together prevents the collapse of vocal culture into either complete uniformity or chaos.