Some oscine songbird species modify their songs throughout their lives (‘adult song plasticity’ or ‘open-ended learning’), while others crystallize their songs around sexual maturity. It remains unknown whether the strength of sexual selection on song characteristics, such as repertoire size, affects adult song plasticity, or whether adult song plasticity affects song evolution. Here, we compiled data about song plasticity, song characteristics, and mating system and then examined evolutionary interactions between these traits. Across 67 species, we found that lineages with adult song plasticity show directional evolution toward increased syllable and song repertoires, while several other song characteristics evolved faster, but in a non-directional manner. Song plasticity appears to drive bi-directional transitions between monogamous and polygynous social mating systems. Notably, our analysis of correlated evolution suggests that extreme syllable and song repertoire sizes drive the evolution of adult song plasticity or stability, providing novel evidence that sexual selection may indirectly influence open- versus closed-ended learning.

Background:The role of Rho family GEFs in dendritic spine formation is currently not well understood. Results: The Rho family GEF Asef2 promotes spine and synapse formation through activation of Rac and spinophilin-mediated localization to spines. Conclusion: Asef2 is a critical regulator of spines and synapses. Significance: Asef2-spinophilin signaling is an important, new mechanism for inducing spine and synapse development.

Birdsong has long been considered a sexually selected trait that relays honest information about male quality, and laboratory studies generally suggest that female songbirds prefer larger repertoires. However, analysis of field studies across species surprisingly revealed a weak correlation between song elaboration and reproductive success, and it remains unknown why only certain species show this correlation in nature. Taken together, these studies suggest that females in numerous species can detect and prefer larger repertoires in a laboratory setting, but larger individual repertoires correlate with reproductive success only in a subset of these species. This prompts the question: Do the species that show a stronger correlation between reproductive success and larger individual repertoires in nature have anything in common? In this study, we test whether between‐species differences in two song‐related variables—species average syllable repertoire size and adult song stability over time—can be used to predict the importance of individual song elaboration in reproductive success within a species. Our cross‐species meta‐analysis of field studies revealed that species with larger average syllable repertoire sizes exhibited a stronger correlation between individual elaboration and reproductive success than species with smaller syllable repertoires. Song stability versus plasticity in adulthood provided little predictive power on its own, suggesting that the putative correlation between repertoire size and age in open‐ended learners does not explain the association between song elaboration and reproductive success.

It has been suggested that cognitive impairments exhibited by people with post-traumatic stress disorder (PTSD) result from intrusive, flashback memories transiently interfering with ongoing cognitive processing. Researchers have further speculated that females are more susceptible to developing PTSD because they form stronger traumatic memories than males, hence females may be more sensitive to the negative effects of intrusive memories on cognition. We have examined how the reminder of a naturalistic stress experience would affect rat spatial memory and if sex was a contributing factor to such effects. Male and female Sprague-Dawley rats were exposed, without contact, to an adult female cat for 30 min. Five weeks later, the rats were trained to locate a hidden platform in the radial-arm water maze and given a single long-term memory test trial 24 h later. Before long-term memory testing, the rats were given a 30-min reminder of the cat exposure experienced 5 weeks earlier. The results indicated that the stress reminder impaired spatial memory in the female rats only. Control manipulations revealed that this effect was not attributable to the original cat exposure adversely impacting learning that occurred 5 weeks later, or to merely exposing rats to a novel environment or predator-related cues immediately before testing. These findings provide evidence that the reminder of a naturalistic stressful experience can impair cognitive processing in rats; moreover, since female rats were more susceptible to the memory-impairing effects of the stress reminder, the findings could lend insight into the existing sex differences in susceptibility to PTSD.