Rapid Effects of Hearing Song on Catecholaminergic Activity in the Songbird Auditory Pathway

Catecholaminergic (CA) neurons innervate sensory areas and affect the processing of sensory signals. For example, in birds, CA fibers innervate the auditory pathway at each level, including the midbrain, thalamus, and forebrain. We have shown previously that in female European starlings, CA activity in the auditory forebrain can be enhanced by exposure to attractive male song for one week. It is not known, however, whether hearing song can initiate that activity more rapidly. Here, we exposed estrogen-primed, female white-throated sparrows to conspecific male song and looked for evidence of rapid synthesis of catecholamines in auditory areas. In one hemisphere of the brain, we used immunohistochemistry to detect the phosphorylation of tyrosine hydroxylase (TH), a rate-limiting enzyme in the CA synthetic pathway. We found that immunoreactivity for TH phosphorylated at serine 40 increased dramatically in the auditory forebrain, but not the auditory thalamus and midbrain, after 15 min of song exposure. In the other hemisphere, we used high pressure liquid chromatography to measure catecholamines and their metabolites. We found that two dopamine metabolites, dihydroxyphenylacetic acid and homovanillic acid, increased in the auditory forebrain but not the auditory midbrain after 30 min of exposure to conspecific song. Our results are consistent with the hypothesis that exposure to a behaviorally relevant auditory stimulus rapidly induces CA activity, which may play a role in auditory responses

Neural Activity Patterns in Response to Interspecific and Intraspecific Variation in Mating Calls in the Túngara Frog

During mate choice, individuals must classify potential mates according to species identity and relative attractiveness. In many species, females do so by evaluating variation in the signals produced by males. Male túngara frogs (Physalaemus pustulosus) can produce single note calls (whines) and multi-note calls (whine-chucks). While the whine alone is sufficient for species recognition, females greatly prefer the whine-chuck when given a choice.To better understand how the brain responds to variation in male mating signals, we mapped neural activity patterns evoked by interspecific and intraspecific variation in mating calls in túngara frogs by measuring expression of egr-1. We predicted that egr-1 responses to conspecific calls would identify brain regions that are potentially important for species recognition and that at least some of those brain regions would vary in their egr-1 responses to mating calls that vary in attractiveness. We measured egr-1 in the auditory brainstem and its forebrain targets and found that conspecific whine-chucks elicited greater egr-1 expression than heterospecific whines in all but three regions. We found no evidence that preferred whine-chuck calls elicited greater egr-1 expression than conspecific whines in any of eleven brain regions examined, in contrast to predictions that mating preferences in túngara frogs emerge from greater responses in the auditory system.Although selectivity for species-specific signals is apparent throughout the túngara frog brain, further studies are necessary to elucidate how neural activity patterns vary with the attractiveness of conspecific mating calls

Declining extra-pair paternity with laying order associated with initial incubation behavior, but independent of final clutch size in the blue tit

Although functional explanations for female engagement in extra-pair copulation have been studied extensively in birds, little is known about how extra-pair paternity is linked to other fundamental aspects of avian reproduction. However, recent studies indicate that the occurrence of extra-pair offspring may generally decline with laying order, possibly because stimulation by eggs induces incubation, which may suppress female motivation to acquire extra-pair paternity. Here we tested whether experimental inhibition of incubation during the laying phase, induced by the temporary removal of eggs, resulted in increased extra-pair paternity, in concert with a later cessation of laying, in blue tits (Cyanistes caeruleus). As expected, experimental females showed a more gradual increase in nocturnal incubation duration over the laying phase and produced larger clutches than controls. Moreover, incubation duration on the night after the first egg was laid predicted how extra-pair paternity declined with laying order, with less incubation being associated with more extra-pair offspring among the earliest eggs in the clutch. However, incubation duration on this first night was unrelated to our experimental treatment and independent of final clutch size. Consequently, the observed decline in extra-pair paternity with laying order was unaffected by our manipulation and larger clutches included proportionally fewer extra-pair offspring. We suggest that female physiological state prior to laying, associated with incubation at the onset of laying, determines motivation to acquire extra-pair paternity independent of final clutch size. This decline in proportion of extra-pair offspring with clutch size may be a general pattern within bird species

Own Song Selectivity in the Songbird Auditory Pathway: Suppression by Norepinephrine

Like human speech, birdsong is a learned behavior that supports species and individual recognition. Norepinephrine is a catecholamine suspected to play a role in song learning. The goal of this study was to investigate the role of norepinephrine in bird's own song selectivity, a property thought to be important for auditory feedback processes required for song learning and maintenance.Using functional magnetic resonance imaging, we show that injection of DSP-4, a specific noradrenergic toxin, unmasks own song selectivity in the dorsal part of NCM, a secondary auditory region.The level of norepinephrine throughout the telencephalon is known to be high in alert birds and low in sleeping birds. Our results suggest that norepinephrine activity can be further decreased, giving rise to a strong own song selective signal in dorsal NCM. This latent own song selective signal, which is only revealed under conditions of very low noradrenergic activity, might play a role in the auditory feedback and/or the integration of this feedback with the motor circuitry for vocal learning and maintenance

Localizing Brain Regions Associated with Female Mate Preference Behavior in a Swordtail

Female mate choice behavior is a critical component of sexual selection, yet identifying the neural basis of this behavior is largely unresolved. Previous studies have implicated sensory processing and hypothalamic brain regions during female mate choice and there is a conserved network of brain regions (Social Behavior Network, SBN) that underlies sexual behaviors. However, we are only beginning to understand the role this network has in pre-copulatory female mate choice. Using in situ hybridization, we identify brain regions associated with mate preference in female Xiphophorus nigrensis, a swordtail species with a female choice mating system. We measure gene expression in 10 brain regions (linked to sexual behavior, reward, sensory integration or other processes) and find significant correlations between female preference behavior and gene expression in two telencephalic areas associated with reward, learning and multi-sensory processing (medial and lateral zones of the dorsal telencephalon) as well as an SBN region traditionally associated with sexual response (preoptic area). Network analysis shows that these brain regions may also be important in mate preference and that correlated patterns of neuroserpin expression between regions co-vary with differential compositions of the mate choice environment. Our results expand the emerging network for female preference from one that focused on sensory processing and midbrain sexual response centers to a more complex coordination involving forebrain areas that integrate primary sensory processing and reward.This work was funded by research fellowships from the University of Texas (UT) Ecology, Evolution and Behavior graduate program (to RYW), along with a Reeder Fellowship, UT SRA, UT StartUp funds, National Science Foundation SGER IOS-0813742 and IOS-0843000 (to MEC). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Biological Sciences, School o

Patterns of nest placement in a population of marsh tits Poecile palustris

The factors influencing nest placement by territorial birds are not fully understood, including the roles played by habitat, conspecific attraction and female experience of a previous nesting location. We used 7 years of Marsh Tit (Poecile palustris) nest-site and territory data, and high-resolution vegetation models derived from remote sensing, to investigate spatial patterns of nest placement with regard to previous female experience and age, conspecific attraction, and habitat in a woodland environment. We found no evidence for an effect of conspecific attraction or previous nest location on nest placement within the territory. However, first-year (FY) females placed nests in a random spatial pattern within their territories, and after first-year (AFY) females predominantly placed nests within the central parts of their territories, away from conspecifics. The core area of each breeding territory was centred on a region of comparatively taller overstorey and less understorey than other parts of the territory. Nest-sites were situated in localised areas of a similar structure, although absolute differences between selected and non-selected areas of the territory were not substantial. Both female age groups nested in areas of the territory where the overstorey contained relatively more Common Ash (Fraxinus excelsior) and Field Maple (Acer campestre), which may have been related to tree height, but there was no selection for English Oak (Quercus robur). We found no significant habitat differences between the territories of FY and AFY females that explained their differing patterns of nest placement