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Anhedonia—defined behaviorally by persistently low motivation and inability to experience pleasure—is common to depressive disorders and portends worse long-term course. Although it has been recognized as a feature of chronic and recurrent depression since the late 19th Century, specifying the etiopathophysiology of anhedonia is a recent development. In this chapter, we selectively review genetic, neural, and epigenetic mechanisms of anhedonia, as well as environmental influences on the trait. Recent conceptualizations describe anhedonia as transdiagnostic and, therefore, not specific to depressive disorders. This observation helps to explain historically perplexing patterns of comorbidity between depression and other psychiatric conditions. Although assessment of anhedonia is relatively straightforward, its neural substrates present challenges for therapeutic intervention. We discuss these challenges and provide suggestions for future research.

In tissue engineering, autofluorescence of polymer scaffolds often lowers the image contrast, making it difficult to examine cells and subcellular structures. Treating the scaffold materials with Sudan Black B (SBB) after cell fixation can effectively suppress autofluorescence, but this approach is not conducive to live cell imaging. Post-culture SBB treatment also disrupts intracellular structures and leads to reduced fluorescence intensity of the targets of interest. In this study, we introduce pre-culture SBB treatment to suppress autofluorescence, where SBB is applied to polymeric scaffold materials before cell seeding. The results show that the autofluorescence signals emitted from polycaprolactone (PCL) scaffolds in three commonly used fluorescence channels effectively decrease without diminishing the fluorescence signals emitted from the cells. The pre-culture SBB treatment does not significantly affect cell viability. The autofluorescence suppressive effect does not substantially diminish during the culturing period up to 28 days. The results also show that cell migration, proliferation, and myogenic differentiation in pre-culture SBB-treated groups do not exhibit statistical difference from the non-treated groups. As such, this approach greatly improves the fluorescence image quality for examining live cell behaviors and dynamics while the cells are cultured within autofluorescent polymer scaffolds.

Low resting respiratory sinus arrhythmia (RSA) is observed in many mental health conditions, including anxiety disorders, mood disorders, schizophrenia spectrum disorders, disruptive behavior disorders, and nonsuicidal self-injury, among others. Findings for RSA reactivity are more mixed. We evaluate associations between RSA reactivity and empirically derived structural categories of psychopathology-including internalizing, externalizing, and thought problems-among physically healthy adults. We searched multiple electronic databases for studies of RSA among participants who were assessed either dimensionally using well-validated measures or diagnostically using structured interviews. Strict inclusion criteria were used to screen 3,605 published reports, which yielded 37 studies including 2,347 participants and 76 effect sizes. We performed a meta-analysis, with meta-analytic regressions of potential moderators, including psychopathology subtypes. The sample-wide meta-analytic association between RSA reactivity and psychopathology was quite small, but heterogeneity was considerable. Moderation analyses revealed significant RSA reactivity (withdrawal) specifically in externalizing samples. Additional moderators included (a) stimulus conditions used to elicit RSA reactivity (only negative emotion inductions were effective), (b) sex (women showed greater RSA reactivity than men), and (c) adherence to established methodological guidelines (e.g., higher electrocardiographic sampling rates yielded greater RSA reactivity). These findings indicate that associations between RSA reactivity and psychopathology are complex and suggest that future studies should include more standardized RSA assessments to increase external validity and decrease measurement error.