One of the most prolific chemical and anatomical imaging techniques of recent decades, magnetic resonance imaging (MRI), includes the ability to noninvasively assess neurochemical changes with magnetic resonance spectroscopy (MRS). Practical concerns are paramount in applying MRS, such as what the manufacturer provides with a routine MRI scanner, what methods are well tolerated by patients, and what has proved most diagnostically productive over a 25 year span of preliminary exploration of the technology. In this review, the authors explain the technical and neurochemical aspects of MRS and critically discuss its clinical neuroimaging applications.

Most adults experience episodes of gingivitis, which can progress to the irreversible, chronic state of periodontitis. However the mechanistic roles of plaque in gingivitis onset and progression to periodontitis remain elusive. Here, we integrated the longitudinal multi-omics data from plaque metagenome, metabolome and salivary cytokines in 40 adults who transit from naturally-occurring gingivitis (NG), to healthy gingivae (baseline) and then to experimental gingivitis (EG). During EG, rapid and consistent alterations in plaque microbiota, metabolites and salivary cytokines emerged as early as 24-72 hours after pause of oral hygiene, defining an asymptomatic 'sub-optimal health' (SoH) stage. SoH also features a steep and synergetic decrease of plaque-derived betaine and Rothia spp., suggesting an anti-gum-inflammation mechanism by health-promoting microbial residents. Global, cross-cohort meta-analysis revealed a high Microbiome-based Periodontitis Index at SoH state, due to its convergent taxonomical and functional profiles towards those of periodontitis. In contrast, caries SoH features a microbial signature very distinct from caries. Thus SoH is a universal state of polymicrobial inflammations with disease-specific features, which is key to maintaining a disease-preventive plaque.