title: Exploring sex differences in the adult zebra finch brain: In vivo diffusion tensor imaging and ex vivo super-resolution track density imaging.
abstract: Zebra finches are an excellent model to study the process of vocal learning, a complex socially-learned tool of communication that forms the basis of spoken human language. So far, structural investigation of the zebra finch brain has been performed ex vivo using invasive methods such as histology. These methods are highly specific, however, they strongly interfere with performing whole-brain analyses and exclude longitudinal studies aimed at establishing causal correlations between neuroplastic events and specific behavioral performances. Therefore, the aim of the current study was to implement an in vivo Diffusion Tensor Imaging (DTI) protocol sensitive enough to detect structural sex differences in the adult zebra finch brain. Voxel-wise comparison of male and female DTI parameter maps shows clear differences in several components of the song control system (i.e. Area X surroundings, the high vocal center (HVC) and the lateral magnocellular nucleus of the anterior nidopallium (LMAN)), which corroborate previous findings and are in line with the clear behavioral difference as only males sing. Furthermore, to obtain additional insights into the 3-dimensional organization of the zebra finch brain and clarify findings obtained by the in vivo study, ex vivo DTI data of the male and female brain were acquired as well, using a recently established super-resolution reconstruction (SRR) imaging strategy. Interestingly, the SRR-DTI approach led to a marked reduction in acquisition time without interfering with the (spatial and angular) resolution and SNR which enabled to acquire a data set characterized by a 78μm isotropic resolution including 90 diffusion gradient directions within 44h of scanning time. Based on the reconstructed SRR-DTI maps, whole brain probabilistic Track Density Imaging (TDI) was performed for the purpose of super resolved track density imaging, further pushing the resolution up to 40μm isotropic. The DTI and TDI maps realized atlas-quality anatomical maps that enable a clear delineation of most components of the song control and auditory systems. In conclusion, this study paves the way for longitudinal in vivo and high-resolution ex vivo experiments aimed at disentangling neuroplastic events that characterize the critical period for vocal learning in zebra finch ontogeny.
authors.affiliation: Bio-Imaging Lab, Department of Biomedical Sciences, University of Antwerp, Belgium.
authors.forename: Julie
authors.initials: J
authors.lastname: Hamaide
authors.affiliation: Bio-Imaging Lab, Department of Biomedical Sciences, University of Antwerp, Belgium.
authors.forename: Geert
authors.initials: G
authors.lastname: De Groof
authors.affiliation: iMinds-Vision Lab, Department of Physics, University of Antwerp, Belgium.
authors.forename: Gwendolyn
authors.initials: G
authors.lastname: Van Steenkiste
authors.affiliation: iMinds-Vision Lab, Department of Physics, University of Antwerp, Belgium.
authors.forename: Ben
authors.initials: B
authors.lastname: Jeurissen
authors.affiliation: Bio-Imaging Lab, Department of Biomedical Sciences, University of Antwerp, Belgium.
authors.forename: Johan
authors.initials: J
authors.lastname: Van Audekerke
authors.affiliation: Bio-Imaging Lab, Department of Biomedical Sciences, University of Antwerp, Belgium.
authors.forename: Maarten
authors.initials: M
authors.lastname: Naeyaert
authors.affiliation: Bio-Imaging Lab, Department of Biomedical Sciences, University of Antwerp, Belgium.
authors.forename: Lisbeth
authors.initials: L
authors.lastname: Van Ruijssevelt
authors.affiliation: GIGA Neurosciences, Research Group in Behavioral Neuroendocrinology, University of Liège, Belgium.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Cornil
authors.affiliation: iMinds-Vision Lab, Department of Physics, University of Antwerp, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Sijbers
authors.affiliation: Bio-Imaging Lab, Department of Biomedical Sciences, University of Antwerp, Belgium.
authors.forename: Marleen
authors.initials: M
authors.lastname: Verhoye
authors.affiliation: Bio-Imaging Lab, Department of Biomedical Sciences, University of Antwerp, Belgium. Electronic address: annemie.vanderlinden@uantwerpen.be.
authors.forename: Annemie
authors.initials: A
authors.lastname: Van der Linden
mesh_terms: D000818:Animals; D016880:Anisotropy; D001921:Brain / Q000033:anatomy & histology* / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D056324:Diffusion Tensor Imaging; D005260:Female; D046369:Finches / Q000033:anatomy & histology* / Q000502:physiology*; D053400:High Vocal Center / Q000033:anatomy & histology / Q000502:physiology; D007091:Image Processing, Computer-Assisted; D008297:Male; D009412:Nerve Fibers / Q000502:physiology; D012727:Sex Characteristics
keywords: DTI; Songbird; Super-resolution reconstruction; Tractography; Voxel-based analysis; Zebra finch