Enhanced characterization of the zebrafish brain as revealed by super-resolution track-density imaging

Abstract

Abstract:In this study we explored the use of super-resolution track density imaging (TDI) for neuroanatomical characterization of the adult zebrafish brain. We compared the quality of image contrast and resolution obtained with T 2 * magnetic resonance imaging (MRI), diffusion tensor based imaging (DTI), TDI, and histology. The anatomical structures visualized in 5 µm TDI maps corresponded with histology. Moreover the super-resolution property and the local-directional information provided by directionally-encoded color TDI facilitated delineation of a larger number of brain regions, commissures and small white matter tracks when compared to conventional MRI and DTI. In total, we were able to visualize 17 structures that were previously unidentifiable using MR microimaging, such as the four layers of the optic tectum. This study demonstrates the use of TDI for characterization of the adult zebrafish brain as a pivotal tool for future phenotypic examination of transgenic models of neurological diseases.

Quantification of voxel-wise total fibre density: Investigating the problems associated with track-count mapping

“…without SIFT or without any of the length-scaled related variants) therefore still has an important role to play, not as a quantitative map, but rather as a high-contrast anatomical image, particularly when used with super-resolution. This quality was in fact exploited in a number of recent TDI studies, including studies in ex vivo mouse brain (Calamante et al, 2012a;Kurniawan et al, 2014;Richards et al, 2014), ex vivo zebrafish brain (Ullmann et al, 2015), and in vivo human brain (Cho et al, 2015;Palesi et al, 2014). These studies demonstrate that there is still an important role for the high contrast standard TDI maps, regardless of this contrast originating in part from tractography biases.…”

“…In conclusion, while standard TDI might be preferable in applications when high anatomical contrast is required, particularly when combined with super-resolution (Calamante et al, , 2012aCho et al, 2015;Kurniawan et al, 2014;Richards et al, 2014;Ullmann et al, 2015), for voxel-wise quantitation of total tract density at native resolution, the AFD total maps are preferable to TDI or other related track-count maps. Nevertheless, it is worth noting that any such voxel-averaged approaches discard important information that is retained in fibre-specific approaches to quantitative comparison (Assaf and Basser, 2005;Dell'Acqua et al, 2013;Raffelt et al, 2012c).…”

“…The technique of track density imaging (TDI) was introduced as a qualitative tractography mapping method due to its high anatomical contrast (Calamante et al, , 2012aCho et al, 2015;Kurniawan et al, 2014;Richards et al, 2014;Ullmann et al, 2015). However, the fact that this contrast is based on variations in the number of streamlines traversing different voxels makes it appear appealing as a potential surrogate measure of 'fibre density', since voxels with high TDI intensity correspond to regions with a large number of streamlines in the whole-brain fibre tracking dataset (i.e.…”

Mapping somatosensory connectivity in adult mice using diffusion MRI tractography and super-resolution track density imaging

“…These findings would not result from connectivity between adjacent layer IV barrels (Feldmeyer, 2012) and, although there is evidence to suggest a higher concentration of myelin within the septal area compared to barrel hollows (Barrera et al, 2012), myelin is not essential for anisotropic diffusion in nerve fibres, with evidence of minor amounts of anisotropy in rodent and piglet cortex (Hoehn-Berlage et al, 1999;Mori et al, 2001;Thornton et al, 1997). In fact, anisotropy from un-myelinated nerves in garfish (Beaulieu and Allen, 1994), rodent (Seo et al, 1999), zebrafish (Ullmann et al, 2013) and human fetal brain (Tucciarone et al, 2009) suggest the radial alignment of microstructure including cell membranes is a sufficient barrier to diffusion to result in anisotropic diffusivity. In addition, complex biological architecture may influence the degree of anisotropy, including axon thickness, density and extracellular space (Beaulieu, 2002).…”

A Model Program for Translational Medicine in Epilepsy Genetics

“…Zebrafish are an established in vivo model for neuroscience and medical research. 33 They possess a high genetic homology (80%–85%) to humans, 34 a central nervous system with a similar brain archetype, 35,36 and conserved neurochemistry. 37 Zebrafish were first established as a model for epilepsy in 2005.…”