Listen and learn.

In songbirds, deafening leads to changes in gene expression which have now been mapped at the single-cell level across the neural circuit involved in song production.

Acceptability of Implants for HIV Treatment in Young Children: Perspectives of Health Care Providers in Johannesburg, South Africa.

In South Africa, less than half of children receiving antiretroviral therapy are virally suppressed. Adherence challenges include poor palatability of drugs and high pill burden. Subcutaneous implants offer a long-acting alternative to daily oral dosing regimens, which may improve outcomes in children living with HIV (CLWH). Qualitative in-depth interviews were conducted with 24 health care providers (HCPs) in Johannesburg, South Africa. Interviews were audio-recorded and transcribed. Data were coded and analyzed using NVivo 12 software and a Grounded Theory approach. Most HCPs welcomed an implant option for CLWH. Perceived benefits included fewer clinic visits, improved adherence, and "normalization" of the lives of CLWH. Concerns included painful insertion and removal, the potential for stigmatization, and caregivers' likely rejection of biodegradable implants. A single, small, non-transparent rod with some flexibility was preferred by most participants. HCP training and early outreach to mitigate potential misinformation about implants and caregivers' fears about biodegradable implants were emphasized. Further engagement with caregivers of CLWH is required and ongoing.

Experience selectively alters functional connectivity within a neural network to predict learned behavior in juvenile songbirds.

One of the central questions of neuroethology is how specialized brain areas communicate to form dynamic networks that support complex cognitive and behavioral processes. Developmental song learning in the male zebra finch songbird (Taeniopygia guttata) provides a unique window into the complex interplay among sensory, sensorimotor, and motor network nodes. The foundation of a young male's song structure is the sensory memory he forms during interactions with an adult "tutor." However, even in the absence of tutoring, juveniles produce a song-like behavior. Thus, by controlling a juvenile male's tutor exposure, we can examine how tutor experience affects distributed neural networks and how network properties predict behavior. Here, we used longitudinal, resting-state fMRI (rs-fMRI) functional connectivity (FC) and song analyses to examine known nodes of the song network, and to allow discovery of additional areas functionally related to song learning. We present three major novel findings. First, tutor deprivation significantly reduced the global FC strength of the caudomedial nidopallium (NCM) subregion of the auditory forebrain required for sensory song learning. Second, tutor deprivation resulted in reduced FC between NCM and cerebellar lobule VI, a region analogous to areas that regulate limbic, social, and language functions in humans. Third, NCM FC strength predicted song stereotypy and mediated the relationship between tutoring and stereotypy, thus completing the link between experience, neural network properties, and complex learned behavior.

Gene manipulation to test links between genome, brain and behavior in developing songbirds: a test case.

Songbird research has made many seminal contributions to the fields of ethology, endocrinology, physiology, ecology, evolution and neurobiology. Genome manipulation is thus a promising new methodological strategy to enhance the existing strengths of the songbird system to advance and expand fundamental knowledge of how genetic sequences and regulation of genomic function support complex natural learned behaviors. In zebra finches (Taeniopygia guttata) in particular, a rich set of questions about the complex process of developmental song learning in juvenile males has been defined. This Review uses one area of zebra finch song learning to demonstrate how genome editing can advance causal investigations into known genome-brain-behavior relationships. Given the number and diversity of songbird species, comparative work leveraging genome manipulation would expand the influence of these birds in additional fields of ecology and evolution for song learning and other behaviors.

Inhibitory cell populations depend on age, sex, and prior experience across a neural network for Critical Period learning.

In many ways, the complement of cell subtypes determines the information processing that a local brain circuit can perform. For example, the balance of excitatory and inhibitory (E/I) signaling within a brain region contributes to response magnitude and specificity in ways that influence the effectiveness of information processing. An extreme example of response changes to sensory information occur across Critical Periods (CPs). In primary mammalian visual cortex, GAD65 and parvalbumin inhibitory cell types in particular control experience-dependent responses during a CP. Here, we test how the density of GAD65- and parvalbumin-expressing cells may inform on a CP for complex behavioral learning. Juvenile male zebra finch songbirds (females cannot sing) learn to sing through coordinated sensory, sensorimotor, and motor learning processes distributed throughout a well-defined neural network. There is a CP for sensory learning, the process by which a young male forms a memory of his "tutor's" song, which is then used to guide the young bird's emerging song structure. We quantified the effect of sex and experience with a tutor on the cell densities of GAD65- and parvalbumin-expressing cells across major nodes of the song network, using ages that span the CP for tutor song memorization. As a resource, we also include whole-brain mapping data for both genes. Results indicate that inhibitory cell populations differ across sex, age, and experiential conditions, but not always in the ways we predicted.

An Acoustic Password Enhances Auditory Learning in Juvenile Brood Parasitic Cowbirds.

How does a naive, young animal decide from which adults to learn behavior? Obligate brood parasitic birds, including brown-headed cowbirds (Molothrus ater), face a particular challenge in learning species-specific behaviors; they lay their eggs in the nest of another species, and juveniles are raised without exposure to adult conspecifics. Nevertheless, male cowbirds need to learn a conspecific song to attract appropriate mates, and female cowbirds need to learn to identify conspecific males for mating. Traditionally, it was thought that parasitic bird species rely purely on instinctual species recognition [1-4], but an alternative is that a species-specific trait serves as a "password" [5], a non-learned cue for naive animals that guides decisions regarding from whom to learn. Here, we tested the hypothesis that the adult "chatter call" enhances the learning of specific songs in juvenile cowbirds. We exposed acoustically naive juvenile male and female cowbirds to songs paired with chatter calls and found that the chatter call enhanced song production learning in males and induced a neurogenomic profile of song familiarity in females, even for heterospecific songs. Thus, a combination of experience-independent and -dependent mechanisms converges to explain how young cowbirds emerge from another species' nest yet learn behaviors from conspecifics. Identifying whether such password-based mechanisms relate to perceptual and behavioral learning in non-parasitic taxa will contribute to our general understanding of the development of social recognition systems.

The variability of song variability in zebra finch (Taeniopygia guttata) populations.

Birdsong is a classic example of a learned social behaviour. Song behaviour is also influenced by genetic factors, and understanding the relative contributions of genetic and environmental influences remains a major goal. In this study, we take advantage of captive zebra finch populations to examine variation in a population-level song trait: song variability. Song variability is of particular interest in the context of individual recognition and in terms of the neuro-developmental mechanisms that generate song novelty. We find that the Australian zebra finch Taeniopygia guttata castanotis (TGC) maintains higher song diversity than the Timor zebra finch T. g. guttata (TGG) even after experimentally controlling for early life song exposure, suggesting a genetic basis to this trait. Although wild-derived TGC were intermediate in song variability between domesticated TGC populations and TGG, the difference between domesticated and wild TGC was not statistically significant. The observed variation in song behaviour among zebra finch populations represents a largely untapped opportunity for exploring the mechanisms of social behaviour.

Interhemispheric functional connectivity in the zebra finch brain, absent the corpus callosum in normal ontogeny.

Bilaterally symmetric intrinsic brain activity (homotopic functional connectivity; FC) is a fundamental feature of the mammalian brain's functional architecture. In mammals, homotopic FC is primarily mediated by the corpus callosum (CC), a large interhemispheric white matter tract thought to balance the bilateral coordination and hemispheric specialization critical for many complex brain functions, including human language. The CC first emerged with the Eutherian (placental) mammals ∼160 MYA and is not found among other vertebrates. Despite this, other vertebrates also exhibit complex brain functions requiring hemispheric specialization and coordination. For example, the zebra finch (Taeniopygia guttata) songbird learns to sing from tutors much as humans acquire speech and must balance hemispheric specialization and coordination to successfully learn and produce song. We therefore tested whether the zebra finch also exhibits homotopic FC, despite lacking the CC. Resting-state fMRI analyses demonstrated widespread homotopic FC throughout the zebra finch brain across development, including within a network required for learned song that lacks direct interhemispheric structural connectivity. The presence of homotopic FC in a non-Eutherian suggests that ancestral pathways, potentially including indirect connectivity via the anterior commissure, are sufficient for maintaining a homotopic functional architecture, an insight with broad implications for understanding interhemispheric coordination across phylogeny.

Developmental song learning as a model to understand neural mechanisms that limit and promote the ability to learn.

Songbirds famously learn their vocalizations. Some species can learn continuously, others seasonally, and still others just once. The zebra finch (Taeniopygia guttata) learns to sing during a single developmental "Critical Period," a restricted phase during which a specific experience has profound and permanent effects on brain function and behavioral patterns. The zebra finch can therefore provide fundamental insight into features that promote and limit the ability to acquire complex learned behaviors. For example, what properties permit the brain to come "on-line" for learning? How does experience become encoded to prevent future learning? What features define the brain in receptive compared to closed learning states? This piece will focus on epigenomic, genomic, and molecular levels of analysis that operate on the timescales of development and complex behavioral learning. Existing data will be discussed as they relate to Critical Period learning, and strategies for future studies to more directly address these questions will be considered. Birdsong learning is a powerful model for advancing knowledge of the biological intersections of maturation and experience. Lessons from its study not only have implications for understanding developmental song learning, but also broader questions of learning potential and the enduring effects of early life experience on neural systems and behavior.

State Variability in Diagnosed Conditions for IDEA Part C Eligibility.

An infant or toddler can begin the process of receiving Part C early intervention services by having a diagnosed condition with a high probability of developmental delay (Individuals with Disabilities Education Improvement Act, 2004). How states define those diagnosed conditions that begin the initiation process varies widely. Lists of diagnosed conditions were collected from state Part C websites and Part C coordinators for a descriptive analysis. Across 49 states, the District of Columbia, and 4 territories, a final list of 620 unique conditions was compiled. No single condition was listed by all jurisdictions. Hearing impairment was the condition listed by the most states (n = 38), followed by fetal alcohol syndrome (n = 34). Of the 620 conditions, 168 (27%) were listed by only 1 state, 554 (89%) were listed by fewer than 10 states, and 66 (11%) were listed by 10 or more states. Of these 66 conditions, 47 (71%) were listed by fewer than 20 states. Most of these 66 conditions (n = 48; 72.7%) had a prevalence of "very rare or rare," 8 (12%) were "common," 6 (9%) were "very common," and 4 (6.1%) were "unknown." The wide heterogeneity in the number and type of diagnostic conditions listed across states should be further investigated as it may represent imbalances in children with diagnosed conditions gaining access to Part C evaluations and individualized family service plans and potentially the services themselves across states. In addition, providing ready access to lists of diagnosed conditions is a simple step that could help states and Part C programs facilitate access to services.

Epigenetic regulation of transcriptional plasticity associated with developmental song learning.

Ethologists discovered over 100 years ago that some lifelong behavioural patterns were acquired exclusively during restricted developmental phases called critical periods (CPs). Developmental song learning in zebra finches is one of the most striking examples of a CP for complex learned behaviour. After post-hatch day 65, whether or not a juvenile male can memorize the song of a 'tutor' depends on his experiences in the month prior. If he experienced a tutor, he can no longer learn, but if he has been isolated from hearing a tutor the learning period is extended. We aimed to identify how tutor experience alters the brain and controls the ability to learn. Epigenetic landscapes are modulated by experience and are able to regulate the transcription of sets of genes, thereby affecting cellular function. Thus, we hypothesized that tutor experiences determine the epigenetic landscape in the auditory forebrain, a region required for tutor song memorization. Using ChIPseq, RNAseq and molecular biology, we provide evidence that naturalistic experiences associated with the ability to learn can induce epigenetic changes, and propose transcriptional plasticity as a mediator of CP learning potential.

A complex mTOR response in habituation paradigms for a social signal in adult songbirds.

Nonassociative learning is considered simple because it depends on presentation of a single stimulus, but it likely reflects complex molecular signaling. To advance understanding of the molecular mechanisms of one form of nonassociative learning, habituation, for ethologically relevant signals we examined song recognition learning in adult zebra finches. These colonial songbirds learn the unique song of individuals, which helps establish and maintain mate and other social bonds, and informs appropriate behavioral interactions with specific birds. We leveraged prior work demonstrating behavioral habituation for individual songs, and extended the molecular framework correlated with this behavior by investigating the mechanistic Target of Rapamycin (mTOR) signaling cascade. We hypothesized that mTOR may contribute to habituation because it integrates a variety of upstream signals and enhances associative learning, and it crosstalks with another cascade previously associated with habituation, ERK/ZENK. To begin probing for a possible role for mTOR in song recognition learning, we used a combination of song playback paradigms and bidirectional dysregulation of mTORC1 activation. We found that mTOR demonstrates the molecular signatures of a habituation mechanism, and that its manipulation reveals the complexity of processes that may be invoked during nonassociative learning. These results thus expand the molecular targets for habituation studies and raise new questions about neural processing of complex natural signals.

Bidirectional manipulation of mTOR signaling disrupts socially mediated vocal learning in juvenile songbirds.

Early life experiences can have long-lasting behavioral consequences because they are encoded when the brain is most malleable. The mechanistic target of rapamycin (mTOR) signaling cascade modulates experience-dependent synaptic plasticity, among other processes. mTOR has been almost exclusively examined in adult rodent learning models, but may be especially important in organizing neural circuits required for developmental acquisition of meaningful complex behaviors. It is among the most commonly implicated factors in neurodevelopmental autism spectrum disorders (ASD), characterized, in part, by distinct social and communication phenotypes. Here, we investigated mTOR in juvenile zebra finch songbirds. Much as children learn language, young male zebra finches need to interact socially with an adult tutor to learn a meaningful song. The memory of the tutor's song structure guides the juvenile's own song, which it uses to communicate for the rest of its life. We hypothesized that mTOR is required for juveniles to learn song. To this end, we first discovered that hearing song activates mTOR signaling in a brain area required for tutor song memorization in males old enough to copy song but not in younger males or females, who cannot sing. We then showed that both inhibition and constitutive activation of mTOR during tutor experiences significantly diminished tutor song copying. Finally, we found that constitutive mTOR activation lowered a behavioral measure of the juvenile's social engagement during tutor experiences, mirroring the relationship in humans. These studies therefore advance understanding about the effects of experience in the context of neurodevelopmental disorders and typical neural development.

A reliable and flexible gene manipulation strategy in posthatch zebra finch brain.

Songbird models meaningfully contribute to many fields including learned vocal communication, the neurobiology of social interactions, brain development, and ecology. The value of investigating gene-brain-behavior relationships in songbirds is therefore high. Viral infections typically used in other lab animals to deliver gene editing constructs have been less effective in songbirds, likely due to immune system properties. We therefore leveraged the in vivo electroporation strategy used in utero in rodents and in ovo in poultry, and apply it to posthatch zebra finch songbird chicks. We present a series of experiments with a combination of promoters, fluorescent protein genes, and piggyBac transposase vectors to demonstrate that this can be a reliable, efficient, and flexible strategy for genome manipulation. We discuss options for gene delivery experiments to test circuit and behavioral hypotheses using a variety of manipulations, including gene overexpression, CRISPR/Cas9 gene editing, inducible technologies, optogenetic or DREADD cellular control, and cell type-specific expression.

Influences of non-canonical neurosteroid signaling on developing neural circuits.

Developing neural circuits are especially susceptible to environmental perturbation. Endocrine signaling systems such as steroids provide a mechanism to encode physiological changes and integrate function across various biological systems including the brain. 'Neurosteroids' are synthesized and act within the brain across development. There is a long history of steroids sculpting developing neural circuits; more recently, evidence has demonstrated how neurosteroids influence the early potential for neural circuits to organize and transmit precise information via non-canonical receptor types.

Shared neural substrates for song discrimination in parental and parasitic songbirds.

In many social animals, early exposure to conspecific stimuli is critical for the development of accurate species recognition. Obligate brood parasitic songbirds, however, forego parental care and young are raised by heterospecific hosts in the absence of conspecific stimuli. Having evolved from non-parasitic, parental ancestors, how brood parasites recognize their own species remains unclear. In parental songbirds (e.g. zebra finch Taeniopygia guttata), the primary and secondary auditory forebrain areas are known to be critical in the differential processing of conspecific vs. heterospecific songs. Here we demonstrate that the same auditory brain regions underlie song discrimination in adult brood parasitic pin-tailed whydahs (Vidua macroura), a close relative of the zebra finch lineage. Similar to zebra finches, whydahs showed stronger behavioral responses during conspecific vs. heterospecific song and tone pips as well as increased neural responses within the auditory forebrain, as measured by both functional magnetic resonance imaging (fMRI) and immediate early gene (IEG) expression. Given parallel behavioral and neuroanatomical patterns of song discrimination, our results suggest that the evolutionary transition to brood parasitism from parental songbirds likely involved an "evolutionary tinkering" of existing proximate mechanisms, rather than the wholesale reworking of the neural substrates of species recognition.

Loneliness: clinical import and interventions.

In 1978, when the Task Panel report to the US President's Commission on Mental Health emphasized the importance of improving health care and easing the pain of those suffering from emotional distress syndromes including loneliness, few anticipated that this issue would still need to be addressed 40 years later. A meta-analysis (Masi et al., 2011) on the efficacy of treatments to reduce loneliness identified a need for well-controlled randomized clinical trials focusing on the rehabilitation of maladaptive social cognition. We review assessments of loneliness and build on this meta-analysis to discuss the efficacy of various treatments for loneliness. With the advances made over the past 5 years in the identification of the psychobiological and pharmaceutical mechanisms associated with loneliness and maladaptive social cognition, there is increasing evidence for the potential efficacy of integrated interventions that combine (social) cognitive behavioral therapy with short-term adjunctive pharmacological treatments.

Social information embedded in vocalizations induces neurogenomic and behavioral responses.

Social cues facilitate relationships within communities. Zebra finches form long-term stable mate pairs and produce offspring within a multi-family, multi-generational community that can include hundreds of birds. Males use song to communicate in this complex environment. Males sing as part of their courtship display but also abundantly throughout each day, suggesting a role for their vocal signature outside of a reproductive context. One advantage of a vocal social cue is that it can be exchanged when birds are out of visual contact, as regularly occurs in a zebra finch community. Previous works have demonstrated that females hearing song are affected by their social relationship to the bird singing it, and the immediate social context. Here, we probed the question of whether or not the song itself carried social information, as would be expected from the situations when males sing outside of view of the female. We quantified behavioral and neurogenomic responses to two songs we predicted would have distinct "attractive" qualities in adult females housed in either mixed sex or female-only social communities. Our results show that only mixed sex-housed females show distinctive behavioral and neurogenomic responses to attractive songs. These data are consistent with the idea that the acoustic properties of song carry social information, and that the current social situation modulates the neural and behavioral responses to these signals.

Expression of androgen receptor in the brain of a sub-oscine bird with an elaborate courtship display.

Sex steroids control vertebrate behavior by modulating neural circuits specialized for sex steroid sensitivity. In birds, receptors for androgens (AR) and estrogens (ERα) show conserved expression in neural circuits controlling copulatory and vocal behaviors. Male golden-collared manakins have become a model for evaluating hormonal control of complex physical courtship displays. These birds perform visually and acoustically elaborate displays involving considerable neuromuscular coordination. Androgens activate manakin courtship and AR are expressed widely in spinal circuits and peripheral muscles utilized in courtship. Using in situ hybridization, we report here the distributions of AR and ERα mRNA in the brains of golden-collared manakins. Overall patterns of AR and ERα mRNA expression resemble what has been observed in non-vocal learning species. Notably, however, we detected a large area of AR expression in the arcopallium, a forebrain region that contains a crucial premotor song nucleus in vocal learning species. These results support the idea that AR signaling both centrally and peripherally is responsible for the activation of male manakin courtship, and the arcopallium is likely a premotor site for AR-mediated displays.