Imaging studies of treatment-resistant depression (TRD) have examined brain activity, structure, and metabolite concentrations to identify critical areas of investigation and potential treatment targets. This chapter reviews findings from structural MRI, functional MRI, and magnetic resonance spectroscopy. Decreased connectivity and metabolite concentrations in frontal brain areas appear to characterize TRD, though results are not consistent across studies. Treatments including rapid-acting antidepressants and transcranial magnetic stimulation have shown some efficacy in reversing these changes while alleviating depressive symptoms. However, few TRD imaging studies exist, often with small sample sizes or varied methods, making firm conclusions difficult. Larger studies with unified hypotheses and data sharing could improve characterization of the illness and identify new treatment targets.
Music and ketamine each influence therapeutic outcomes, yet their combined use is rarely studied. This scoping review maps existing research on administering music alongside ketamine or esketamine in humans. Studies include healthy volunteers and patients of various ages, using different doses and treatment processes, with music played at varying times relative to drug administration. Research on music during ketamine anesthesia is included, as anesthesia drove early ketamine use. Recreational ketamine studies are excluded. The review is limited to English-language articles with no year restriction. It is the first comprehensive overview of music and ketamine/esketamine interplay, offering guidance for future study design.