Estrogen‐dependent selectivity of genomic responses to birdsong

Abstract

Behavioral responses to sociosexual signals often depend on gonadal steroid hormones, which are thought to modulate behavior by acting on motivational systems in the brain. There is mounting evidence that sex steroids may also modulate perception of sociosexual signals by affecting sensory processing. In seasonally breeding songbirds such as the white-throated sparrow (Zonotrichia albicollis), the female's behavioral response to hearing male song depends on her plasma levels of estradiol (E2). Here, we examined whether plasma E2 also affects the selectivity of the song-induced zenk (egr-1) response in the auditory forebrain, which is known to vary according to the behavioral relevance of song stimuli. Non-breeding females were held on a winter-like photoperiod and implanted with silastic capsules containing either no hormone or E2. E2-treated birds hearing 42 min of conspecific song had more cells immunoreactive for the protein product of zenk in the auditory forebrain than did those hearing frequency-matched synthetic tones. In birds not treated with E2, however, the zenk response to song did not differ from that to tones. We found similar effects in the avian homolog of the inferior colliculus, indicating that E2 may affect the processing of auditory information upstream of the forebrain. Our data suggest that in females, zenk induction in the auditory system is selective for song only when plasma E2 exceeds non-breeding levels. E2-dependent plasticity of auditory pathways and processing centres may promote recognition of and attention to conspecific song during the breeding season.

Prior experience with conspecific signals enhances auditory midbrain responsiveness to conspecific vocalizations

“…In this study we used expression of the immediate early gene egr-1 as a surrogate for neural excitation, an approach that has frequently been used to explore the reception of conspecific mating signals (Hoke et al, 2004;Sockman et al, 2005;Maney et al, 2006;Wong et al, 2012). It is important to note, however, that immediate early genes are themselves important regulators of further genomic action.…”

Estradiol Shapes Auditory Processing in the Adult Brain by Regulating Inhibitory Transmission and Plasticity-Associated Gene Expression

“…It is clear that the plasma levels of gonadal steroids impact a variety of social behaviors, including the perception of, and responsiveness to, sociosexual signals (Sisneros et al, 2004;Maney et al, 2006;Lynch and Wilczynski, 2008). Such a role of sex steroid hormones in vertebrates results from activity within a "social behavioral network" that includes sexual motivational brain areas such as the medial preoptic area of the hypothalamus and the medial extended amygdala (Newman, 1999;Goodson, 2005).…”

“…Such a role of sex steroid hormones in vertebrates results from activity within a "social behavioral network" that includes sexual motivational brain areas such as the medial preoptic area of the hypothalamus and the medial extended amygdala (Newman, 1999;Goodson, 2005). However, recent evidence indicates that sex steroid hormones may directly impact sensory processing in a variety of vertebrate species, including humans, monkeys, fish, and frogs (Sisneros et al, 2004;Wilczynski, 2006, 2008;Maney et al, 2006). Although the site of action of such hormone-driven alterations in sensory processing may vary across species, our work indicates that the impact of steroid hormones may be exerted directly on primary sensory areas, through both rapid modulation of neuronal responsiveness and long-term gene expression-dependent mechanisms.…”

Avian ecologists and physiologists have different sexual preferences

“…A second way of getting around the problem that wild-caught females hardly adapt to captive settings is to increase their responsiveness by injecting them with exogenous hormones such as steroids or Gonadotropin Releasing Hormone (GnRH). These techniques have mostly been used in studies investigating behavioral responses of females to male song [2,8], but have also been helpful in physiological studies [27,51,74,73,79,80,102,127,135].…”