Abstract
The detection of animate beings at the onset of life is important for phylogenetically distant species, such as birds and primates. Naïve chicks preferentially approach a stimulus resembling a conspecific (a stuffed fowl) over a less naturalistic one (a scrambled version of the stuffed fowl, presenting the same low-level visual features as the fowl in an unnatural configuration). The neuronal mechanisms underlying this behavior are mostly unknown. However, it has been hypothesized that innate social predispositions may involve subpallial brain areas including the amygdala. Here we asked whether a stuffed hen would activate areas of the arcopallium/amygdala complex, in particular the nucleus taeniae of the amygdala (TnA) or septum. We measured brain activity by visualizing the immediate early gene product c-Fos. After exposure to the hen, TnA showed higher density of c-Fos expressing neurons, compared to chicks that were exposed to the scrambled stimulus. A similar trend was present in the lower portion of the arcopallium, but not in the upper portion of the arcopallium or in the septum. This demonstrates that at birth the TnA is already engaged in responses to social visual stimuli, suggesting an important role for this nucleus in the early ontogenetic development of social behavior.
Highlights
One of the earliest expressions of social behavior in newborn vertebrates is a preference to attend to visual stimuli that resemble conspecifics, including stimuli with face-like configurations or biological motion
The expression of immediate early gene (IEG) is tightly linked to neuronal activity and visualizing c-Fos expression in brain sections offers an effective approach to studying neuronal activation in specific brain areas, a technique commonly applied to mammals and birds[16,17,18,19,20,21,22,23]
Www.nature.com/scientificreports previous studies we found that exposure to the static configuration of features or to the natural motion typical of conspecifics resulted in differential activation in an area involved in filial imprinting, as well as in the arcopallium/amygdala complex and in septal and preoptic nuclei[25,26,27,28]
Summary
One of the earliest expressions of social behavior in newborn vertebrates is a preference to attend to visual stimuli that resemble conspecifics, including stimuli with face-like configurations or biological motion. Www.nature.com/scientificreports previous studies we found that exposure to the static configuration of features or to the natural motion typical of conspecifics resulted in differential activation in an area involved in filial imprinting (the intermediate medial mesopallium, IMM), as well as in the arcopallium/amygdala complex (a term that has been introduced by Herold et al.[24], to describe a region that combines arcopallium and TnA) and in septal and preoptic nuclei[25,26,27,28] The latter three areas are part of the so-called ‘social behavior network’, which is shared among all vertebrates and comprises interconnected areas rich in sex steroid receptors and implicated in adult social behaviors[29,30,31]. In an altricial species, the zebra finch, the TnA can already be delineated at post-hatching day one[51], suggesting that TnA has the potential to be fully functional during social interactions already at the time of hatching or soon after
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