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Major depressive disorder (MDD) is characterized by psychomotor retardation whose underlying neural source remains unclear. Psychomotor retardation may either be related to a motor source like the motor cortex or, alternatively, to a psychomotor source with neural changes outside motor regions, like input regions such as visual cortex. These two alternative hypotheses in main (n = 41) and replication (n = 18) MDD samples using 7 Tesla MRI are investigated. Analyzing both global and local connectivity in primary motor cortex (BA4), motor network and middle temporal visual cortex complex (MT+), the main findings in MDD are: 1) Reduced local and global synchronization and increased local‐to‐global output in motor regions, which do not correlate with psychomotor retardation, though. 2) Reduced local‐to‐local BA4 – MT+ functional connectivity (FC) which correlates with psychomotor retardation. 3) Reduced global synchronization and increased local‐to‐global output in MT+ which relate to psychomotor retardation. 4) Reduced variability in the psychophysical measures of MT+ based motion perception which relates to psychomotor retardation. Together, it is shown that visual cortex MT+ and its relation to motor cortex play a key role in mediating psychomotor retardation. This supports psychomotor over motor hypothesis about the neural source of psychomotor retardation in MDD. [ABSTRACT FROM AUTHOR]

Objective: Previous studies have found that patients with Major Depressive Disorder (MDD) exhibit impaired visual motion perception capabilities, and multi-level abnormalities in the human middle temporal complex (MT+), a key brain area for processing visual motion information. However, the brain activity pattern of MDD patients during the perception of visual motion information is currently unclear. In order to study the effect of depression on the activity and functional connectivity (FC) of MT+ during the perception of visual motion information, we conducted a study combining task-state fMRI and psychophysical paradigm to compare MDD patients and healthy control (HC)., Methods: Duration threshold was examined through a visual motion perception psychophysical experiment. In addition, a classic block-design grating motion task was utilized for fMRI scanning of 24 MDD patients and 25 HC. The grating moved randomly in one of eight directions. We examined the neural activation under visual stimulation conditions compared to the baseline and FC., Results: Compared to HC group, MDD patients exhibited increased duration threshold. During the task, MDD patients showed decreased beta value and percent signal change in left and right MT+. In the sample comprising MDD and HC, there was a significant negative correlation between beta value in right MT+ and duration threshold. And in MDD group, activation in MT+ were significantly correlated with retardation score. Notably, no such differences in activation were observed in primary visual cortex (V1). Furthermore, when left MT+ served as the seed region, compared to the HC, MDD group showed increased FC with right calcarine fissure and surrounding cortex and decreased FC with left precuneus., Conclusion: Overall, the findings of this study highlight that the visual motion perception function impairment in MDD patients relates to abnormal activation patterns in MT+, and task-related activity are significantly connected to the retardation symptoms of the disease. This not only provides insights into the potential neurobiological mechanisms behind visual motion perception disorder in MDD patients from the aspect of task-related brain activity, but also supports the importance of MT+ as a candidate biomarker region for MDD., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Liu, Hu, Han, Tan and Song.)

Objectives: The present study aimed to explore the circadian rhythm of salivary serotonin in patients with major depressive disorder before and after treatment with fluoxetine and its relationship with clinical therapeutic effect., Methods: This study investigated salivary serotonin in 13 outpatients with major depressive disorder and age- and sex-matched healthy controls. Depressed patients received six weeks fluoxetine treatment (20 mg/day), saliva was collected before and four weeks after treatment. A total of 8 time-point salivary serotonin was measured across the whole day. Multi-oscillator cosinor model was used to fit the rhythms., Results: Serotonin concentration in saliva ranged from 0.32 ng/ml to 9.62 ng/ml. Salivary serotonin showed prominent circadian rhythm in 91% depressed patients and 92% healthy subjects. Circadian amplitude tend to be higher after fluoxetine treatment in depressed patients, so as the ultradian cycle amplitude. The serotonin circadian amplitude (After minus Before) was positively correlated with the decrease of Zung Self-Rating Depression Scale(SDS) scores at day 42 whereas there was no such correlation at day 28. There was no significant difference in the parameters of mesor, acrophase, harmonic and area under curve among three groups., Conclusions: Salivary serotonin in patients with major depressive disorder showed clear circadian rhythm. The relationship between the increase of salivary serotonin amplitude and clinical response deserve further study.

Objectives: The purpose of this study is to explore the response of melatonin circadian rhythm to fluoxetine treatment and its relationship with clinical therapeutic effect., Methods: This study investigated salivary melatonin in 13 outpatients with major depressive disorder and age- and sex-matched healthy controls. Depressed patients received six weeks fluoxetine (20 mg/day) treatment, and saliva was collected before and four weeks after treatment. In sampling days, a total of 12 time-point salivary melatonin was measured over 24-hours. Multioscillator cosinor model was used to fit the rhythms., Results: There was no difference of circadian melatonin rhythms in depressed patients, and melatonin was not significantly lower after fluoxetine treatment. To our surprise, the melatonin amplitude (Before minus After) was positively correlated with the improvement in Hamilton Depression Rating Scale (HDRS) scores at day 42 whereas there was no such correlation at day 28., Conclusions: Melatonin rhythms were similar between depressed patients and matched healthy controls. The interesting finding that the difference of salivary melatonin amplitude was correlated with the clinical improvement after six weeks fluoxetine treatment deserve further study.