Nanostructure-specific X-ray tomography reveals myelin levels, integrity and axon orientations in mouse and human nervous tissue

Myelin insulates neuronal axons and enables fast signal transmission, constituting a key component of brain development, aging and disease. Yet, myelin-specific imaging of macroscopic samples remains a challenge. Here, we exploit myelin’s nanostructural periodicity, and use small-angle X-ray scattering tensor tomography (SAXS-TT) to simultaneously quantify myelin levels, nanostructural integrity and axon orientations in nervous tissue. Proof-of-principle is demonstrated in whole mouse brain, mouse spinal cord and human white and gray matter samples. Outcomes are validated by 2D/3D histology and compared to MRI measurements sensitive to myelin and axon orientations. Specificity to nanostructure is exemplified by concomitantly imaging different myelin types with distinct periodicities. Finally, we illustrate the method’s sensitivity towards myelin-related diseases by quantifying myelin alterations in dysmyelinated mouse brain. This non-destructive, stain-free molecular imaging approach enables quantitative studies of myelination within and across samples during development, aging, disease and treatment, and is applicable to other ordered biomolecules or nanostructures

Building connectomes using diffusion MRI: why, how and but

Why has diffusion MRI become a principal modality for mapping connectomes in vivo? How do different image acquisition parameters, fiber tracking algorithms and other methodological choices affect connectome estimation? What are the main factors that dictate the success and failure of connectome reconstruction? These are some of the key questions that we aim to address in this review. We provide an overview of the key methods that can be used to estimate the nodes and edges of macroscale connectomes, and we discuss open problems and inherent limitations. We argue that diffusion MRI-based connectome mapping methods are still in their infancy and caution against blind application of deep white matter tractography due to the challenges inherent to connectome reconstruction. We review a number of studies that provide evidence of useful microstructural and network properties that can be extracted in various independent and biologically-relevant contexts. Finally, we highlight some of the key deficiencies of current macroscale connectome mapping methodologies and motivate future developments

Undergraduate orientations towards higher education in Germany and England: problematizing the notion of ‘student as customer’

There is a great deal of discussion in the academic literature around how the current conditions in higher education frame students as customers. Observers are of the view that rankings and marketing, an increased focus on student satisfaction, and particularly tuition fees, encourage an instrumental, passive attitude towards a university education. Given the volume of attention directed towards this topic, it is perhaps surprising that there is relatively little scholarship that examines it empirically. Some who have addressed it presumed a customer/consumer orientation in students and have been somewhat—but not entirely successful—in generating evidence to confirm those assumptions. It appears that the expectations of this instrumental, passive orientation are being realised in part, but that this is also mediated by other dispositions. What could be considered to be missing from the analysis thus far is an exploration of how students make university­related decisions (not simply what choices are based on) and how they understand the respective roles of the student and university. This study begins to fill that gap, exploring the orientations towards university of undergraduates in Germany and England, two countries where the diffusion of market conditions in higher education policies has been somewhat contrasting. Distinctions between the German and English students did emerge, but these were less based on those countries’ unequal engagement with tuition fees and rankings and more to do with other aspects of their university cultures and the world beyond their degrees. This suggests that how people approach their time as students is more complex than some of the literature assumes. Furthermore, at the very least, any consideration of this topic must include an analysis of how students themselves understand and experience their higher education and broader social contexts