Song Syllables Research Articles

Song convergence in multiple urban populations of silvereyes (Zosterops lateralis).

Recent studies have revealed differences between urban and rural vocalizations of numerous bird species. These differences include frequency shifts, amplitude shifts, altered song speed, and selective meme use. If particular memes sung by urban populations are adapted to the urban soundscape, “urban-typical” calls, memes, or repertoires should be consistently used in multiple urban populations of the same species, regardless of geographic location. We tested whether songs or contact calls of silvereyes (Zosterops lateralis) might be subject to such convergent cultural evolution by comparing syllable repertoires of geographically dispersed urban and rural population pairs throughout southeastern Australia. Despite frequency and tempo differences between urban and rural calls, call repertoires were similar between habitat types. However, certain song syllables were used more frequently by birds from urban than rural populations. Partial redundancy analysis revealed that both geographic location and habitat characteristics were important predictors of syllable repertoire composition. These findings suggest convergent cultural evolution: urban populations modify both song and call syllables from their local repertoire in response to noise.

Variability of inter-syllable gaps challenges the branched-chain model of sequence production in Bengalese finches

Songbirds have emerged as a premier model system for studying how brain circuits learn and produce complex action sequences. The adult song of the most widely studied songbird, the zebra finch (ZF), consists of repeats of a stereotyped sequence of vocal gestures known as syllables. These songs are incredibly precise, with individual syllables and inter-syllable gaps varying in length by roughly 5% (std. dev.). Electrophysiological recordings in singing birds reveal that song related neural activity is also precise, with individual neurons in the premotor nucleus HVC producing one burst of action potentials per song sequence, locked to song acoustics with sub-millisecond precision [1]. This precision and reliability has led to the suggestion that the HVC circuit is organized as a synfire chain, with activity propagating down a chain-like network of strongly connected groups of neurons [2]. Here we examine the songs of a closely related species, the Bengalese finch (BF). These birds also learn sequences of highly stereotyped syllables. However, sequencing is variable and includes ‘branching’ in which some song syllables can be followed by more than one (2-4) subsequent syllables (fig​(fig1A).1A). Given the many similarities between species, it has been hypothesized that variable sequencing in BF is accomplished by a branched synfire network in HVC [3] (fig​(fig1B).1B). Such a model suggests that timing precision in BFs should be similar to that of ZFs, perhaps with a bit of added variability due to the competition between branches. However, this added variability should not be longer than the maximum latency between successive links in the synfire chain (~20 msec). Figure 1 Variable sequencing of Bengalese finch song A. Transition diagram for single BF; strength of the arrow is proportional to transition probability. B. Branched synfire chain model. C. Median and inter-quartile range of coefficient of variation for BF gaps, ... To test this, we measured the durations of both syllables and inter-syllable gaps in a large sample of BF songs (32 birds, 52,451 transitions between 303 unique syllable pairs; syllables were hand labeled by visual inspection and durations were determined by a hand-set threshold optimized for each bird.) Overall, the mean and coefficient of variation (CV) for BF inter-syllable gap durations were qualitatively more variable than for BF syllables, ZF syllables or ZF gaps, even at syllable transitions that were not branched (fig ​(fig1C).1C). These results contradict the simplest branched synfire chain model of variable sequencing in BFs, and provide significant challenges for more general models based on this idea.

CORRELATED EVOLUTION OF BEAK MORPHOLOGY AND SONG IN THE NEOTROPICAL WOODCREEPER RADIATION

Mating signals may diversify as a byproduct of morphological adaptation to different foraging niches, potentially driving speciation. Although many studies have focused on the direct influence of ecological and sexual selection on signal divergence, the role of indirect mechanisms remains poorly understood. Using phenotypic and molecular datasets, we explored the interplay between morphological and vocal evolution in an avian radiation characterized by dramatic beak variation, the Neotropical woodcreepers (Dendrocolaptinae). We found evidence of a trade-off between the rate of repetition of song syllables and frequency bandwidth: slow paced songs had either narrow or wide frequency bandwidths, and bandwidth decreased as song pace increased. This bounded phenotypic space for song structure supports the hypothesis that passerine birds face a motor constraint during song production. Diversification of acoustic characters within this bounded space was correlated with diversification of beak morphology. In particular, species with larger beaks produced slower songs with narrower frequency bandwidths, suggesting that ecological selection on beak morphology influences the diversification of woodcreeper songs. Because songs in turn mediate mate choice and species recognition in birds, these results indicate a broader role for ecology in avian diversification.

Control of fundamental frequency in zebra finch vocal behavior

Event Abstract Back to Event Control of fundamental frequency in zebra finch vocal behavior Franz Goller1* and Tobias Riede1 1 University of Utah, Biology, United States In the avian syrinx generates sound by flow-induced tissue (labia or membrane) oscillations. The fundamental frequency of sound (F0) arises from a complex interplay of biomechanical and aerodynamic properties as well as neural control of syringeal movements and respiration. Each variable affects labial position and tension either directly or indirectly, and synchronously or independently. In the zebra finch (Taeniopygia guttata), song syllables with low F0 are pulse-tone like and are generated by both sound sources, whereas high-frequency syllables are tonal and are generated by the right side of the syrinx. It has been suggested that these different vibratory modes arise from different dynamical regimes (Sitt et al., Physical Rev E 78,011905, 2008). No major asymmetries exist in the extracellular matrix or size of the left and right labia (Riede et al., PLoS One 5, e11368), suggesting that difference in F0 of the two sides involves aerodynamic and neural mechanisms. Here we investigate the respective roles of all contributing variables in setting F0 of different zebra finch sounds. Ventral syringeal muscle activity increases with increasing F0 for the pulse-tone syllables. For high-frequency syllables, activation is maximal, but is not correlated with differences in F0. The activity of other syringeal muscles (dorsal syringeal, ventral tracheobronchial and dorsal tracheobronchial) shows a similar relationship with F0, indicating that synergistic activation patterns cannot explain F0-control for high-frequency syllables. The possibility that active closing of the left side generates a biomechanical gearing of the effect of right-side tension control by muscles can also be eliminated. Denervation of the left syringeal muscles does not consistently change F0 of right-side generated syllables. The effect of air sac pressure on F0 was investigated by bilateral denervation of the syringeal muscles. F0 increases slightly with increasing air sac pressure (approx. 20-45 Hz per kPa) if neural control of labial tension and position is eliminated. We then asked whether zebra finches compensate for the increase in F0 at higher air sac pressures through muscle control when they vocalize with different sound amplitude. Changes in song amplitude arise from differences in air sac pressure and can be induced by the Lombard effect or by experimentally reducing expiratory volume of air. In both manipulations the air sac pressure changes are accompanied by corresponding changes in F0. The changes in F0 are larger in high-frequency syllables than in low-frequency harmonic stacks. These results suggest that zebra finches do not adjust muscular control of labial tension to compensate for this effect of air sac pressure on F0. These results illustrate how aerodynamic effects and neural control of labial tension interact in setting F0 of song syllables. However, tension control for the high-frequency modal sounds is still not fully understood. Although we can eliminate some hypotheses (gearing, muscle synergies), the precise control mechanism is still unknown. Acknowledgements: supported by NIDCD 06876. Keywords: birdsong, frequency control Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster Presentation (see alternatives below as well) Topic: Sensorimotor Integration Citation: Goller F and Riede T (2012). Control of fundamental frequency in zebra finch vocal behavior. Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00367 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 01 May 2012; Published Online: 07 Jul 2012. * Correspondence: Dr. Franz Goller, University of Utah, Biology, Salt Lake City, Utah, 84112, United States, goller@biology.utah.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Franz Goller Tobias Riede Google Franz Goller Tobias Riede Google Scholar Franz Goller Tobias Riede PubMed Franz Goller Tobias Riede Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Directed and Undirected Songs in Free-Tailed Bats, Implications for Mammalian Vocal Production

Event Abstract Back to Event Directed and Undirected Songs in Free-Tailed Bats, Implications for Mammalian Vocal Production Kirsten Bohn1, 2* and Michael Smotherman2 1 Florida International University, United States 2 Texas A&M, United States Most mammalian vocalizations are innate, inflexible and lack syntactical structure. Not surprisingly, the neurocircuitry of mammalian vocal production also appears relatively simple, being predominantly controlled by brainstem pattern generators. The Brazilian free-tailed bat, Tadarida brasiliensis, is unusual in that it is a mammal that sings like a bird – males produce hierarchically structured songs where specific syllables are combined to form phrases that vary in order and number from one rendition to the next. In songbirds it is known that song variability is generated by an avian analogue of the mammalian striatothalamic feedback pathway to cortex. To date, no mammalian vocalizations other than human speech are known to depend upon this striatothalamic pathway. If free-tailed bats can be shown to vary their songs in ways similar to songbirds, it may provide a unique example of how the striatothalamic circuitry contributes to mammalian vocal communication. The main goal of this project was to determine the contexts in which males sing and whether song flexibility varies with behavioral context. In the wild, males live in dense aggregations, usually in dark caves or crevices that preclude the use of visual cues. Given the environment in which singing occurs, we hypothesized that identifying the right auditory cues could be the key to characterizing batsong production. To test this, we conducted a set of playback experiments on a wild colony at Texas A&M that examined the relative effects of 1) echolocation calls that mimic a bat approaching the roost site and 2) unfamiliar male songs. We compared song responses to these two contextual stimuli with control periods of background noise. During playback experiments, we recorded 699 songs from an estimated 39 different males. Bats responded strongly and robustly to echolocation call stimuli – out of 50 sets of echolocation passes bats responded 74% of the time with 215 songs. During the same interval immediately preceding stimuli, bats sang only 6% of the time producing just three songs. Song responses were also incredibly rapid – initiating within 200 to 500 ms of stimulus onset. Song responses were highly specific to echolocation passes; bats did not respond to unfamiliar male songs even though there is no difference in the spectro-temporal structure of some song syllables and echolocation calls. Running the same experiments in our captive colony we found similar results – we rapidly triggered singing via playbacks of echolocation calls. Bats also sang in the absence of stimuli, but far less frequently. We labeled songs as directed songs if they were produced in response to an echolocation pass and undirected songs if they occurred during control periods. When we compared song structure between the two contexts we found a significant difference in song types and variability. Directed songs were significantly shorter and were more likely to contain buzzes than undirected songs. In conclusion, singing is rapidly triggered in free-tailed bats using echolocation calls and free-tailed bats vary songs across behavior contexts in a manner very similar to songbirds. Keywords: song, Mammal, Vocal-motor, bats, birdsong Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster (but consider for Participant Symposium) Topic: Social Behavior Citation: Bohn K and Smotherman M (2012). Directed and Undirected Songs in Free-Tailed Bats, Implications for Mammalian Vocal Production. Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00068 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 04 Jul 2012; Published Online: 07 Jul 2012. * Correspondence: Dr. Kirsten Bohn, Florida International University, Miami, FL, United States, bohnkirsten@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Kirsten Bohn Michael Smotherman Google Kirsten Bohn Michael Smotherman Google Scholar Kirsten Bohn Michael Smotherman PubMed Kirsten Bohn Michael Smotherman Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Control of Vocal and Respiratory Patterns in Birdsong: Dissection of Forebrain and Brainstem Mechanisms Using Temperature

Learned motor behaviors require descending forebrain control to be coordinated with midbrain and brainstem motor systems. In songbirds, such as the zebra finch, regular breathing is controlled by brainstem centers, but when the adult songbird begins to sing, its breathing becomes tightly coordinated with forebrain-controlled vocalizations. The periods of silence (gaps) between song syllables are typically filled with brief breaths, allowing the bird to sing uninterrupted for many seconds. While substantial progress has been made in identifying the brain areas and pathways involved in vocal and respiratory control, it is not understood how respiratory and vocal control is coordinated by forebrain motor circuits. Here we combine a recently developed technique for localized brain cooling, together with recordings of thoracic air sac pressure, to examine the role of cortical premotor nucleus HVC (proper name) in respiratory-vocal coordination. We found that HVC cooling, in addition to slowing all song timescales as previously reported, also increased the duration of expiratory pulses (EPs) and inspiratory pulses (IPs). Expiratory pulses, like song syllables, were stretched uniformly by HVC cooling, but most inspiratory pulses exhibited non-uniform stretch of pressure waveform such that the majority of stretch occurred late in the IP. Indeed, some IPs appeared to change duration by the earlier or later truncation of an underlying inspiratory event. These findings are consistent with the idea that during singing the temporal structure of EPs is under the direct control of forebrain circuits, whereas that of IPs can be strongly influenced by circuits downstream of HVC, likely in the brainstem. An analysis of the temporal jitter of respiratory and vocal structure suggests that IPs may be initiated by HVC at the end of each syllable and terminated by HVC immediately before the onset of the next syllable.

On the interaction of alliteration with rhythm and metre in popular music

AbstractA number of scholars have written on characteristics of vocal melody in popular music, but little attention has been paid at the level of phonetic detail. This study argues that the phonetic structure of a melody can contribute in important ways to a song's reception and success, given the ways that listeners react and respond to vocalised melody. This article discusses different ways in which stressed syllables in familiar pop songs alliterate, and it investigates the way these patterns interact rhythmically with metre.

Mechanisms and time course of vocal learning and consolidation in the adult songbird

In songbirds, the basal ganglia outflow nucleus LMAN is a cortical analog that is required for several forms of song plasticity and learning. Moreover, in adults, inactivating LMAN can reverse the initial expression of learning driven via aversive reinforcement. In the present study, we investigated how LMAN contributes to both reinforcement-driven learning and a self-driven recovery process in adult Bengalese finches. We first drove changes in the fundamental frequency of targeted song syllables and compared the effects of inactivating LMAN with the effects of interfering with N-methyl-d-aspartate (NMDA) receptor-dependent transmission from LMAN to one of its principal targets, the song premotor nucleus RA. Inactivating LMAN and blocking NMDA receptors in RA caused indistinguishable reversions in the expression of learning, indicating that LMAN contributes to learning through NMDA receptor-mediated glutamatergic transmission to RA. We next assessed how LMAN's role evolves over time by maintaining learned changes to song while periodically inactivating LMAN. The expression of learning consolidated to become LMAN independent over multiple days, indicating that this form of consolidation is not completed over one night, as previously suggested, and instead may occur gradually during singing. Subsequent cessation of reinforcement was followed by a gradual self-driven recovery of original song structure, indicating that consolidation does not correspond with the lasting retention of changes to song. Finally, for self-driven recovery, as for reinforcement-driven learning, LMAN was required for the expression of initial, but not later, changes to song. Our results indicate that NMDA receptor-dependent transmission from LMAN to RA plays an essential role in the initial expression of two distinct forms of vocal learning and that this role gradually wanes over a multiday process of consolidation. The results support an emerging view that cortical-basal ganglia circuits can direct the initial expression of learning via top-down influences on primary motor circuitry.

Relative salience of envelope and fine structure cues in zebra finch song

Zebra finches produce a learned song that is rich in harmonic structure and highly stereotyped. More is generally known about how birds learn and produce this song than how they perceive it. Here, zebra finches were trained with operant techniques to discriminate changes in natural and synthetic song motifs. Results show that zebra finches are quite insensitive to changes to the overall envelope of the motif since they were unable to discriminate more than a doubling in inter-syllable interval durations. By contrast, they were quite sensitive to changes in individual syllables. A series of tests with synthetic song syllables, including some made of frozen noise and Schroeder harmonic complexes, showed that birds used a suite of acoustic cues in normal listening but they could also distinguish among syllables simply on the basis of the temporal fine structure in the waveform. Thus, while syllable perception is maintained by multiple redundant cues, temporal fine structure features alone are sufficient for syllable discrimination and may be more important for communication than previously thought.

Dual Pre-Motor Contribution to Songbird Syllable Variation

Many forms of learning, including songbird vocal learning, rely on the brain's ability to use pre-motor variation and sensory feedback to guide behavior toward a specific target or goal. In the vocal control system of zebra finches (Taeniopygia guttata) the pre-motor mechanisms of vocal variation are thought to be vested primarily in a neural pathway that includes the basal ganglia. A second circuit that includes avian analogues of mammalian pre-motor and motor cortex (the vocal motor pathway) generates the patterned structure of learned adult song. Here, we tested the ability of the basal ganglia pathway to generate pre-motor vocal variation within the spectral and temporal dimensions of zebra finch song structure. In adult birds, ablation of the basal ganglia pathway significantly reduced the spectral and temporal dispersion of individual song syllables, with the exception of syllable pitch, where the reduction was not statistically significant when compared against surgical controls. We found a similar pattern of results using longitudinal comparisons (juvenile vs adult) to isolate the contribution of the basal ganglia pathway to spectral dispersion in populations of developing song syllables--variation in syllable pitch was significantly smaller than in all other measured spectral features. The results indicate that pre-motor variation generated by the basal ganglia pathway may be sufficient to adjust vocal output toward highly acoustically dispersed targets of imitation, but suggest that complete acquisition of the pronounced variation in syllable pitch that characterizes adult song will necessitate a gradual developmental interaction between the basal ganglia and vocal motor pathways.

Disrupting vagal feedback affects birdsong motor control.

Coordination of different motor systems for sound production involves the use of feedback mechanisms. Song production in oscines is a well-established animal model for studying learned vocal behavior. Whereas the online use of auditory feedback has been studied in the songbird model, very little is known about the role of other feedback mechanisms. Auditory feedback is required for the maintenance of stereotyped adult song. In addition, the use of somatosensory feedback to maintain pressure during song has been demonstrated with experimentally induced fluctuations in air sac pressure. Feedback information mediating this response is thought to be routed to the central nervous system via afferent fibers of the vagus nerve. Here, we tested the effects of unilateral vagotomy on the peripheral motor patterns of song production and the acoustic features. Unilateral vagotomy caused a variety of disruptions and alterations to the respiratory pattern of song, some of which affected the acoustic structure of vocalizations. These changes were most pronounced a few days after nerve resection and varied between individuals. In the most extreme cases, the motor gestures of respiration were so severely disrupted that individual song syllables or the song motif were atypically terminated. Acoustic changes also suggest altered use of the two sound generators and upper vocal tract filtering, indicating that the disruption of vagal feedback caused changes to the motor program of all motor systems involved in song production and modification. This evidence for the use of vagal feedback by the song system with disruption of song during the first days after nerve cut provides a contrast to the longer-term effects of auditory feedback disruption. It suggests a significant role for somatosensory feedback that differs from that of auditory feedback.

Comparative study of long-term reduction of high-frequency song syllables in deafened zebra and Bengalese finches: implications for the role of auditory feedback in song maintenance

Auditory feedback is necessary for adult song maintenance in both oscines and psittacines. Although belonging to phylogenically separated orders, deafened adult oscine Bengalese finches and psittacine budgerigars exhibit similarities in certain aspects of song changes. An interesting question is whether these birds share common mechanisms for song maintenance. Therefore, it is important to compare the effects of deafening on adult song patterns among and within orders. Although zebra and Bengalese finches are closely related oscine species, few studies have performed direct, long-term, quantitative comparisons of their songs after deafening because suitable song characteristics have not been identified. Based on our previous findings for Bengalese finch songs, we analyzed zebra finch songs over 9 months after deafening, focusing on changes in the number of syllables categorized according to fundamental frequencies. Deafened zebra finches demonstrated a gradual but significant decrease in high-frequency syllables and a tendency to increase low-frequency syllables, similar to deafened Bengalese finches. Although this change took longer in zebra finches, the altered proportion of syllables eventually stabilized. Results indicated that adult songs show similar aspects after auditory deprivation, and that neural mechanisms involved in the maintenance of high-frequency song syllables, using auditory feedback, may be present in both finches despite species differences.

Evidence that a Singing Impediment is Caused by Impaired Interhemispheric Coordination of Brain Activity

The neural network that mediates learned vocalizations in oscine songbirds provides a useful animal model for understanding the neural mechanisms mediating certain aspects of human speech. We studied the song impairment in zebra finches caused by unilateral lesion of nucleus Uvaeformis (Uva), a thalamic nucleus important for song production, as a model for the human speech impediments that can arise after brain injury. We observed an immediate degradation of singing premotor neural activity in the HVC (a brain nucleus encoding higher‐order features of song) after unilateral Uva lesion, as well as a loss of coordination of singing premotor activity across the hemispheres. To establish a more direct link between interhemispheric coordination of brain activity and the quality of song syllables produced, we compared HVC neural activity in lesioned birds during production of the most consistently formed song syllables (“Good”) vs the most poorly formed syllables (“Evil”). We discovered a significant difference in time‐specific synchronizing signals between Good and Evil syllables. This provides some of the most conclusive evidence that impairment of interhemispheric coordination is the physiological basis for some vocal impediments. Supported by the Howard Hughes Medical Institute through the Undergraduate Science Education Program, the ASU School of Life Sciences and the Barrow Neurological Foundation.

Relative salience of acoustic features in zebra finch song.

Zebra finch song consists of complex acoustic elements repeated over several hundred milliseconds with extreme vocal-motor precision. Much less is known about how song is perceived though previous work has shown that zebra finches easily discriminate between normal and time-reversed versions of song syllables. Here, we used operant conditioning, psychophysical methods, and various synthetic song models to assess the bird’s sensitivity to local versus global temporal changes in song and to determine which cues are most salient in these complex syllables. Birds could discriminate syllable reversals in songs made up of the song envelope filled with noise, suggesting that syllable envelope cues can provide the basis for discrimination. However, birds could also discriminate syllable reversals in songs made up entirely of Schroeder harmonic complexes, stimuli that provide only phase (reversals of fine structure) cues without syllable envelope cues. Birds performed better on longer syllables, suggesting a window of temporal integration for fine structure discrimination. In contrast, humans could perceive few of the syllable reversals within these song modifications. This fine-grained perception in birds suggests that the machinery used for song perception is as precise as the machinery used for song production. [Work supported by NIH.]

Neuronal Stability and Drift across Periods of Sleep: Premotor Activity Patterns in a Vocal Control Nucleus of Adult Zebra Finches

How stable are neural activity patterns compared across periods of sleep? We evaluated this question in adult zebra finches, whose premotor neurons in the nucleus robustus arcopallialis (RA) exhibit sequences of bursts during daytime singing that are characterized by precise timing relative to song syllables. Each burst has a highly regulated pattern of spikes. We assessed these spike patterns in singing that occurred before and after periods of sleep. For about half of the neurons, one or more premotor bursts had changed after sleep, an average of 20% of all bursts across all RA neurons. After sleep, modified bursts were characterized by a discrete, albeit modest, loss of spikes with compensatory increases in spike intervals, but not changes in timing relative to the syllable. Changes in burst structure followed both interrupted bouts of sleep (1.5-3 h) and full nights of sleep, implicating sleep and not circadian cycle as mediating these effects. Changes in burst structure were also observed during the day, but far less frequently. In cases where multiple bursts in the sequence changed in a single cell, the sequence position of those bursts tended to cluster together. Bursts that did not show discrete changes in structure also showed changes in spike counts, but not biased toward losses. We hypothesize that changes in burst patterns during sleep represent active sculpting of the RA network, supporting auditory feedback-mediated song maintenance.

Whatever Happened to Ethology? The Case for the Fixed Action Pattern in Psychology.

In the 1950s ethology entered British psychology as an antidote to learning theory, as a re-incarnation of instinct theory, and as a paradigm for human attachment processes. In the 1970s it became simply the study of “natural” behaviour in an evolutionary framework and was replaced by socio-biology and evolutionary psychology, in which species comparisons and evolutionary relationships enable adaptational (i.e. functional) explanations of human behaviours. Ethological theory had been abandoned. Yet the concept of the fixed action pattern (FAP) is the behavioural equivalent of the species in biology. Both identify constancies in variety. Together with the concepts sign stimulus, innate releaser, specific action potential (SAP), displacement activity, appetitive and consummatory behaviour, complex behaviour can be understood as interacting elements for which there should be neuro-hormonal and genetic systems (i.e. mechanisms). An analysis of the nature of emotion using ethological theory is presented as an example. Neuro-ethological work began in the 1960s with brain lesions and stimulation, and continues with modern technologies. For example, syllables in bird song (FAPs?) are correlated with activity in a striatal brain region (HVc) and a gene (FoxP2) – a gene that affects speech. An outline of the ethology and neuro-ethology of speech is presented.

Opioid modulation of song in male zebra finches ( Taenopygia guttata)

Endogenous opioids are known to modulate motivated behaviors. Male zebra finches produce a highly motivated behavior (directed song) to court females and also sing in isolation (undirected song). We found that adult male zebra finches sang significantly fewer directed and undirected songs after administration of low doses (2.5 mg/kg body weight) of the general opioid antagonist naloxone, even though the order of syllables in songs was not altered. Surprisingly, high doses of naloxone (10 mg/kg body weight) dramatically decreased the production of undirected songs but had no significant effects on directed songs. There were no changes in the number of calls during directed or undirected song, movement, stereotyped behaviors including pecking and preening, feeding or drinking behaviors after naloxone administration. We also found that treating zebra finches with naloxone led to a decrease in tonality (goodness of pitch), frequency and amplitude modulation and an increase in the length of intersyllable intervals. Our results suggest that the opioid system can differentially modulate directed and undirected song as well as the acoustic characteristics of birdsong, perhaps by acting on different components of the song control system.

Information Content in Chorus Songs of the Group‐Living Australian Magpie (Cracticus tibicen dorsalis) in Western Australia

AbstractSongs of birds encode several kinds of information that may be used during interactions with conspecifics. Some bird species live in social groups and perform territorial advertisement song as a group. Group singing raises questions concerning its function in the social life of the group. Australian magpies (Cracticus tibicen = Gymnorhina tibicen) are group‐living birds that sing chorus songs known as carols. Each carol is composed of a series of individual syllables. Previous spectrographic descriptions of carols in eastern Australian populations found individual‐specific and sex‐specific acoustic characteristics in carol syllables and group‐specific characteristics in carol songs. These findings suggest that carols might reveal not only the identity of the group, but also other properties, such as its size and sex composition, which could influence outcomes in assessment/management interactions between groups. I tape‐recorded and analyzed carols of seven magpie groups in Western Australia, a location and subspecies (C. t. dorsalis) differing from the previous studies of singing by magpies. I analyzed carols of each group to determine acoustic features of syllables, syllable syntax within carols and the way carols are delivered as a repertoire. Visual classification of individual song syllables as seen on sound spectrograms, automated quantification of spectral features of song syllables, examination for carol repertoires and call‐answer syntax within carols all revealed little evidence that magpies have individual‐specific or group‐specific vocal characteristics. Thus, chorus songs do not appear sufficiently distinctive to communicate identity at the level of the group nor reveal group size and composition. Instead, caroling may signal only territory occupancy and willingness to participate in territorial defense. A new hypothesis is advanced suggesting that chorus songs of group‐living birds are an unselected consequence of the coordinated duet songs of the breeding male and female whose duets are joined adventitiously by other group members.

Syntactical complexity of songs in the Black-browed Reed Warbler Acrocephalus bistrigiceps

Abstract The transition patterns of syllables (syntactical complexity) in songs of the Black-browed Reed Warbler (Acrocephalus bistrigiceps) were more complex than previously measured in the domestic bird, the Bengalese Finch (Lonchura striata var. domestica). Syntactical complexity was correlated with song duration (song length), which implies that these song characteristics have a similar function, probably in sexual selection. Syntactical complexity was not correlated with repertoire size (the number of syllable types), which is another presumable sexually selected trait but may not be important in this species, as previously suggested. Future studies on birdsongs should focus on not only repertoire size but also syntactical complexity.

A statistical method for quantifying songbird phonology and syntax

Songbirds are the preeminent animal model for understanding how the brain encodes and produces learned vocalizations. Here, we report a new statistical method, the Kullback–Leibler (K–L) distance, for analyzing vocal change over time. First, we use a computerized recording system to capture all song syllables produced by birds each day. Sound Analysis Pro software [Tchernichovski O, Nottebohm F, Ho CE, Pesaran B, Mitra PP. A procedure for an automated measurement of song similarity. Anim Behav 2000;59:1167–76] is then used to measure the duration of each syllable as well as four spectral features: pitch, entropy, frequency modulation, and pitch goodness. Next, two-dimensional scatter plots of each day of singing are created where syllable duration is on the x-axis and each of the spectral features is represented separately on the y-axis. Each point in the scatter plots represents one syllable and we regard these plots as random samples from a probability distribution. We then apply the standard information-theoretic quantity K–L distance to measure dissimilarity in phonology across days of singing. A variant of this procedure can also be used to analyze differences in syllable syntax.