An atlas for human brain myelin content throughout the adult life span

Abstract

Myelin water imaging is a quantitative neuroimaging technique that provides the myelin water fraction (MWF), a metric highly specific to myelin content, and the intra-/extra-cellular T2 (IET2), which is related to water and iron content. We coupled high-resolution data from 100 adults with gold-standard methodology to create an optimized anatomical brain template and accompanying MWF and IET2 atlases. We then used the MWF atlas to characterize how myelin content relates to demographic factors. In most brain regions, myelin content followed a quadratic pattern of increase during the third decade of life, plateau at a maximum around the fifth decade, then decrease during later decades. The ranking of mean myelin content between brain regions remained consistent across age groups. These openly available normative atlases can facilitate evaluation of myelin imaging results on an individual basis and elucidate the distribution of myelin content between brain regions and in the context of aging.

Age‐related estimates of aggregate g‐ratio of white matter structures assessed using quantitative magnetic resonance neuroimaging

“…These results are consistent with a pattern of brain maturation through middle age followed by a rapid decline, in agreement with postmortem observations (Peters, 2002;Tang, Nyengaard, Pakkenberg, & Gundersen, 1997). Indeed, previous studies have revealed inverted Ushape trends of MWF with age in different brain structures (Arshad et al, 2016;Dvorak et al, 2021); although MWF represents a very different metric than aggregate g-ratio, both of these indices are expected to correlate with overall extent and quality of myelination. In addition, we found that different regions exhibited similarities, as well as differences, in the associations between aggregate g-ratio and age, with most regions peaking during the fifth decade of life.…”

“…Further, our results indicate a quadratic association between MVF and age in all white matter regions (Table 2 and Figure 5b). These results agree with our and others' recent studies indicating an inverted Ushape association of myelin content with age in several white matter regions (Arshad et al, 2016;Dvorak et al, 2021). The quadratic association between MVF and age is attributed to the process of myelination from youth through middle age, followed by demyelination in later years (Arshad et al, 2016;Bartzokis et al, 2010); this pattern is in agreement with postmortem observations (Peters, 2002;Tang et al, 1997).…”

“…In a pioneering MRI study, conducted on a cohort of adult subjects spanning a wide age range, based on MT and NODDI imaging, Cercignani and colleagues have found that the aggregate g-ratio increases linearly with age (Cercignani et al, 2017), interpreted as reduction in myelin throughout adulthood and decreased axonal density at older ages. However, this is difficult to reconcile with reports of increased myelination throughout adulthood followed by a decrease at older ages (Arshad, Stanley, & Raz, 2016;Dvorak et al, 2021;Qian, Khattar, Cortina, Spencer, & Bouhrara, 2020). As discussed by the authors, this discrepancy is likely due to use of MT imaging for the estimation of MVF which, while sensitive to myelin content, is not specific, as well as to other technical considerations, including a limited cohort size.…”

Cervical cord myelin abnormality is associated with clinical disability in multiple sclerosis

“…However, previous MWI studies demonstrated good intersite (mean MWF coefficient of variation (COV) = 4.68 %) and inter-vendor (mean MWF COV = 2.77 %) reproducibility. 18,33 34 disease duration appears to play a more important role in ProgMS than RRMS in our cohorts (Figure 3); understanding the impact of these different characteristics of the groups warrants further exploration in a larger cohort. Another factor worthy of consideration is that we scanned the cervical cord, particularly C2/C3 level, rather than the whole spinal cord.…”

Escitalopram Administration, Neuroplastic Effects and Relearning: A Diffusion Tensor Imaging Study in Healthy Individuals

“…On the basis of imaging studies, convincing evidence points towards a relation between white matter integrity, plasticity and intellectual development of the central nervous system during child-and adulthood (Wang and Young, 2014;Bells et al, 2019). Apart from age-related changes of white matter throughout lifespan, which peak in the third and decline from the fifth decade onward (Dvorak et al, 2021), longitudinal neuroimaging studies revealed an effect of experience on white matter that can be traced with diffusion weighted imaging (Zatorre et al, 2012). Investigations in animals and humans show that white matter changes dynamically and dependent of the standardized study-experience in vivo following training (Keller and Just, 2009;Blumenfeld-Katzir et al, 2011).…”