Questioning Seasonality of Neuronal Plasticity in the Adult Avian Brain

Tatyana Pozner,Anat Barnea,Stan Moaraf,Rachel Heiblum,Yulia Vistoropsky

doi:10.1038/s41598-018-29532-1

Tatyana Pozner, Anat Barnea + Show 3 more

Open Access

https://doi.org/10.1038/s41598-018-29532-1

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Abstract

To date, studies that reported seasonal patterns of adult neurogenesis and neuronal recruitment have correlated them to seasonal behaviors as the cause or as a consequence of neuronal changes. The aim of our study was to test this correlation, and to investigate whether there is a seasonal pattern of new neuronal recruitment that is not correlated to behavior. To do this, we used adult female zebra finches (songbirds that are not seasonal breeders), kept them under constant social, behavioral, and spatial environments, and compared neuronal recruitment in their brains during two seasons, under natural and laboratory conditions. Under natural conditions, no significant differences were found in the pattern of new neuronal recruitment across seasons. However, under artificial indoor conditions that imitated the natural conditions, higher neuronal recruitment occurred in late summer (August) compared to early spring (February). Moreover, our data indicate that “mixing” temperature and day length significantly reduces new neuronal recruitment, demonstrating the importance of the natural combination of temperature and day length. Taken together, our findings show, for the first time, that neuroplasticity changes under natural vs. artificial conditions, and demonstrate the importance of both laboratory and field experiments when looking at complex biological systems.

Highlights

Brain plasticity is correlated to migratory behavior in birds
Do seasonal environmental changes cause changes in behavior, which, in turn, cause changes in brain nuclei that are associated with this behavior? Or do seasonal environmental changes cause changes in brain nuclei, which, in turn, cause changes in behavior? Brenowitz[14] presents evidence for the latter suggestion, arguing that seasonal changes in the song nuclei in seasonal species are predominantly regulated by hormonal changes, and that the subsequent changes in song behavior play a secondary role in reinforcing neuronal changes
As already detailed in the Introduction, we focused our attention on three brain regions (Fig. 3A): The Hippocampal complex (HC), Nidopallium Caudale (NC), and Medial Striatum (MSt)

Summary

Introduction

Brain plasticity is correlated to migratory behavior in birds. We have found that in passerines, more new neurons are recruited in the migrant reed warbler (Acrocephalus scirpaceus) than in the resident Clamorous warbler (A. stentoreus), in two forebrain regions that are known to process spatial information - the Hippocampus (HC) and the Nidopallium Caudolaterale (NCL), during spring, summer and autumn[6]. They suggested that the variation in the seasonal change in the HC of food-storing parids is the result of various experience-dependent effects, such as the intensity of the behavior, stress, or the amount of exercise in captivity Another comprehensive recent review by Pravosudov et al.[12] on two food-storing species – black capped and mountain chickadees, pointed to inconsistencies between results from different studies regarding the seasonal effect on neuronal recruitment in the HC. In both species they found that rates of new neuronal recruitment in the HC were significantly associated with winter climate harshness, with birds from harsher climates having higher neurogenesis rates. To the best of our knowledge, this assumption has not been tested yet

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