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1. Neuroestrogen synthesis modifies neural representations of learned song without altering vocal imitation in developing songbirds

   https://doi.org/10.1038/s41598-020-60329-3  

   Vahaba, Daniel M. ; Hecsh, Amelia ; Remage-Healey, Luke ( February 2020 , Scientific Reports)

   Birdsong learning, like human speech, depends on the early memorization of auditory models, yet how initial auditory experiences are formed and consolidated is unclear. In songbirds, a putative cortical locus is the caudomedial nidopallium (NCM), and one mechanism to facilitate auditory consolidation is 17β-estradiol (E2), which is associated with human speech-language development, and is abundant in both NCM and human temporal cortex. Circulating and NCM E2 levels are dynamic during learning, suggesting E2’s involvement in encoding recent auditory experiences. Therefore, we tested this hypothesis in juvenile male songbirds using a comprehensive assessment of neuroanatomy, behavior, and neurophysiology. First, we found that brain aromatase expression, and thus the capacity to synthesize neuroestrogens, remains high in the auditory cortex throughout development. Further, while systemic estrogen synthesis blockade suppressed juvenile song production, neither systemic nor unilateral E2 synthesis inhibition in NCM disrupted eventual song imitation. Surprisingly, early life neuroestrogen synthesis blockade in NCM enhanced the neural representations of both the birds’ own song and the tutor song in NCM and a downstream sensorimotor region, HVC, respectively. Taken together, these findings indicate that E2 plays a multifaceted role during development, and that, contrary to prediction, tutor song memorization is unimpaired by unilateral estrogen synthesis blockade in the auditory cortex.

    

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

   https://doi.org/10.1002/dneu.22589  

   Merullo, Devin P. ; Asogwa, Chinweike N. ; Sanchez‐Valpuesta, Miguel ; Hayase, Shin ; Pattnaik, Bikash R. ; Wada, Kazuhiro ; Riters, Lauren V. ( March 2018 , Developmental Neurobiology)

   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.NtsandNtsr1mRNA 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).Ntsexpression in LMAN during the subsong stage was lower compared to other time points.Ntsr1expression 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 receiveNts. The expression changes at crucial time points for song development are similar to changes observed in dopamine studies and suggestNtsmay be involved in the process of vocal learning. © 2018 Wiley Periodicals, Inc. Develop Neurobiol 78: 671–686, 2018

    

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3. Female zebra finches do not sing yet share neural pathways necessary for singing in males

   https://doi.org/10.1002/cne.24569  

   Shaughnessy, Derrick W. ; Hyson, Richard L. ; Bertram, Richard ; Wu, Wei ; Johnson, Frank ( December 2018 , Journal of Comparative Neurology)

   Adult female zebra finches (Taeniopygia guttata), which do not produce learned songs, have long been thought to possess only vestiges of the forebrain network that supports learned song in males. This view ostensibly explains why females do not sing—many of the neural populations and pathways that make up the male song control network appear rudimentary or even missing in females. For example, classic studies of vocal‐premotor cortex (HVC, acronym is name) in male zebra finches identified prominent efferent pathways from HVC to vocal‐motor cortex (RA, robust nucleus of the arcopallium) and from HVC to the avian basal ganglia (Area X). In females, by comparison, the efferent targets of HVC were thought to be only partially innervated by HVC axons (RA) or absent (Area X). Here, using a novel visually guided surgical approach to target tracer injections with precision, we mapped the extrinsic connectivity of the adult female HVC. We find that female HVC shows a mostly male‐typical pattern of afferent and efferent connectivity, including robust HVC innervation of RA and Area X. As noted by earlier investigators, we find large sex differences in the volume of many regions that control male singing (male > female). However, sex differences in volume were diminished in regions that convey ascending afferent input to HVC. Our findings do not support a vestigial interpretation of the song control network in females. Instead, our findings support the emerging view that the song control network may have an altogether different function in nonsinging females.

    

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4. Territory Quality Predicts Avian Vocal Performance Across an Urban-Rural Gradient

   https://doi.org/10.3389/fevo.2020.587120  

   Phillips, Jennifer N. ; Cooper, W. Justin ; Luther, David A. ; Derryberry, Elizabeth P. ( December 2020 , Frontiers in Ecology and Evolution)

   Human activity around the globe is a growing source of selection pressure on animal behavior and communication systems. Some animals can modify their vocalizations to avoid masking from anthropogenic noise. However, such modifications can also affect the salience of these vocalizations in functional contexts such as competition and mate choice. Such is the case in the well-studied Nuttall's white-crowned sparrow ( Zonotrichia leucophrys nuttalli ), which lives year-round in both urban San Francisco and nearby rural Point Reyes. A performance feature of this species' song is salient in territorial defense, such that higher performance songs elicit stronger responses in simulated territorial intrusions; but songs with lower performance values transmit better in anthropogenic noise. A key question then is whether vocal performance signals male quality and ability to obtain high quality territories in urban populations. We predicted white-crowned sparrows with higher vocal performance will be in better condition and will tend to hold territories with lower noise levels and more species-preferred landscape features. Because white-crowned sparrows are adapted to coastal scrub habitats, we expect high quality territories to contain lower and less dense canopies, less drought, more greenness, and more flat open ground for foraging. To test our predictions, we recorded songs and measured vocal performance and body condition (scaled mass index and fat score) for a set of urban and rural birds ( N = 93), as well as ambient noise levels on their territories. Remote sensing metrics measured landscape features of territories, such as drought stress (NDWI), greenness (NDVI), mean canopy height, maximum height, leaf area density (understory and canopy), slope, and percent bare ground for a 50 m radius on each male territory. We did not find a correlation between body condition and performance but did find a relationship between noise levels and performance. Further, high performers held territories with lower canopies and less dense vegetation, which are species-preferred landscape features. These findings link together fundamental aspects of sexual selection in that habitat quality and the quality of sexually selected signals appear to be associated: males that have the highest performing songs are defending territories of the highest quality. 

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5. De novo assembly and annotation of the singing mouse genome

   https://doi.org/10.1186/s12864-023-09678-7  

   Smith, Samantha K. ; Frazel, Paul W. ; Khodadadi-Jamayran, Alireza ; Zappile, Paul ; Marier, Christian ; Okhovat, Mariam ; Brown, Stuart ; Long, Michael A. ; Heguy, Adriana ; Phelps, Steven M. ( September 2023 , BMC Genomics)

   Developing genomic resources for a diverse range of species is an important step towards understanding the mechanisms underlying complex traits. Specifically, organisms that exhibit unique and accessible phenotypes-of-interest allow researchers to address questions that may be ill-suited to traditional model organisms. We sequenced the genome and transcriptome of Alston’s singing mouse (Scotinomys teguina), an emerging model for social cognition and vocal communication. In addition to producing advertisement songs used for mate attraction and male-male competition, these rodents are diurnal, live at high-altitudes, and are obligate insectivores, providing opportunities to explore diverse physiological, ecological, and evolutionary questions.

   Using PromethION, Illumina, and PacBio sequencing, we produced an annotated genome and transcriptome, which were validated using gene expression and functional enrichment analyses. To assess the usefulness of our assemblies, we performed single nuclei sequencing on cells of the orofacial motor cortex, a brain region implicated in song coordination, identifying 12 cell types.

   These resources will provide the opportunity to identify the molecular basis of complex traits in singing mice as well as to contribute data that can be used for large-scale comparative analyses.

    

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