Uncovering a 'sensitive window' of multisensory and motor neuroplasticity in the cerebrum and cerebellum of male and female starlings.

Jasmien Orije,Emilie Cardon,Elisabeth Jonckers,Veerle M Darras,Marleen Verhoye,Julie Hamaide,Annemie Van Der Linden

doi:10.7554/elife.66777

Abstract

Traditionally, research unraveling seasonal neuroplasticity in songbirds has focused on the male song control system and testosterone. We longitudinally monitored the song behavior and neuroplasticity in male and female starlings during multiple photoperiods using Diffusion Tensor and Fixel-Based techniques. These exploratory data-driven whole-brain methods resulted in a population-based tractogram confirming microstructural sexual dimorphisms in the song control system. Furthermore, male brains showed hemispheric asymmetries in the pallium, whereas females had higher interhemispheric connectivity, which could not be attributed to brain size differences. Only females with large brains sing but differ from males in their song behavior by showing involvement of the hippocampus. Both sexes experienced multisensory neuroplasticity in the song control, auditory and visual system, and cerebellum, mainly during the photosensitive period. This period with low gonadal hormone levels might represent a 'sensitive window' during which different sensory and motor systems in the cerebrum and cerebellum can be seasonally re-shaped in both sexes.

Highlights

Various songbird species demonstrate different levels of female song, in one of the most studied song bird species, the zebra finch, female song is absent (Odom et al, 2014)
The male focus proceeded in the research of seasonal neuroplasticity, since this process was shown to be largely driven by photoperiod-induced increases in testosterone, which results in a pre-optic area (POA)-mediated increase in motivation to sing and subsequent singing activity-induced neuroplasticity (Alward et al, 2013)
We recognize many of the white matter structures such as the different lamina, occipito-mesencephalic tract (OM) and optic tract (TrO) among others

Summary

Introduction

Various songbird species demonstrate different levels of female song, in one of the most studied song bird species, the zebra finch, female song is absent (Odom et al, 2014) Observations like these led to the discovery of one of the largest sexual dimorphisms in the brain of vertebrate species (Bernard et al, 1993; Nottebohm and Arnold, 1976). Such sexual dimorphisms in singing behavior and brain structure drove a bias in research of the song control system toward male songbirds (Figure 1B). The main emphasis on the role of photoperiodicinduced increase in testosterone has led to many manipulation studies involving castration and/or testosterone implantation and its effect on song production and the song control system (e.g. Hall and Macdougall-Shackleton, 2012; Orije et al, 2020; Stevenson and Ball, 2010)

Methods

Results

Conclusion