Growing new brain cells enhanced by social contact

From the editor's choice section of the May 30 issue of Science, a suggestion that increased social input from a larger number of other animals enhances the survival of new brain cells in brain areas involved in communication:

Out With the Old, In With the New

Might this adage, which some pundits have claimed as the basis for the vernal electoral calamities that have befallen the Labour Party in the United Kingdom, apply equally forcefully to the turnover of neurons in the brain? Adar et al. have performed a painstaking histological and immunofluorescence accounting of the survival likelihoods of newly born neurons in the brain of the zebra finch, a songbird that serves as an animal model for studying innate and learned influences on vocal communication. They focused on the nidopallium caudale (NC) region because it participates in auditory processing and is activated by social stimuli (other songbirds in this notably social species). By varying the complexity of the social environment, they found that the youngest cells--which had recently migrated from the site of their birth and were still becoming integrated, quite literally, as they established syn-aptic connections with existing NC neurons--were more likely to have survived if the bird had been exposed to a large group of male and female birds; conversely, in birds housed with only one other individual, the survival of older (though still relatively young) cells was enhanced. One interpretation of these data is that an increase in demand--in the form of an upturn in auditory/social inputs needing to be processed--acts as a selective pressure favoring the survival of new recruits.