Purpose Glutamate is the most abundant neurotransmitter in the brain, and proton magnetic resonance spectroscopy (MRS) allows quantification of glutamate-related metabolites (glutamate/glutamine complex; Glx). In previous findings, Glx has been lower in several brain regions of patients with major depressive disorder than in those of healthy controls. However, the physiologic and characteristic distribution of Glx in the same individual remains unclear. We attempted to clarify which brain regions reflect changes associated with depression.Material and method We measured Glx in 12 patients with depression and 12 healthy controls matched for age and sex in three brain regions (left amygdala, left anterior cingulate cortex, and left dorsolateral prefrontal cortex), and then compared the physiologic and characteristic distribution of Glx between the two groups.Results In comparisons of the distributions, Glx was significantly higher in the amygdala than in other regions. Glx tended to be lower among the patients than the controls, although no significant differences were present between the groups. We could not detect the changes expected from major depressive disorder (reduced Glx) in the amygdala, which regulates emotions and shows higher concentrations of Glx than other regions.Conclusion Previous studies have suggested that the concentration of Glx decreases with age, and this might have influenced our results regarding changes with major depressive disorder. In addition, we could not clarify whether medications affected the patient condition, because treatment for depression increased Glx in previous studies. Further MRS studies are needed to clarify Glx distributions in the specific diagnosis of depression.
We found the robust statistical laws of behavioral organization, specifically the laws of durations of resting and active periods in spontaneous physical activity (SPA), as well as their alterations in psychiatric disorders, including major depressive disorder. These strongly suggest the existence of the dynamical system organizing SPA and its dysfunctions in the disorders. In this talk, we introduce our recent studies on the reconstruction of the dynamical systems based on SPA in patients with psychiatric disorders, showing the alterations of their dynamical properties in the disorders. Further, using the intensive longitudinal data of SPA in patients with bipolar disorder, we demonstrate the concurrent changes of the reconstructed systems, associated with pathological states or clinical phases, along with the nontrivial changes around the vicinity of clinical phase transitions. These could lead to the objective monitoring of pathological states of psychiatric disorders and an early warning detection of pathological changes.