Major depressive disorder (MDD) has a higher incidence in recent years and lays a high economic burden on families and society, in general. Early diagnosis and treatment are essential while the criteria could be used for diagnosis are now not available. Magnetic resonance imaging (MRI) is an essential noninvasive tool for mental disorders. Dr. Junfeng Li from the Department of Radiology, Heping Hospital of Changzhi Medical College, Shan Xi, China has been working in the field of depression and applications of MRI for years. He and the co-author summarized the recent MRI findings on the neural manifestations of MDD based on related articles and discussed the potential of MRI biomarkers that may be useful for early diagnosis and evaluation of treatment outcomes for MDD.
As the corresponding author of the paper, Dr. Li, summarizes various MRI techniques which have been used to explore the functional alterations of MDD. Among these, resting-state fMRI plays a role in its ability to reflect an individual's natural mental state and help to shed light on the psychological basis of disease. ReHo, ALFF, fALFF, and FC are commonly used parameters, and abnormalities were shown compared to healthy controls. Abnormal ReHo values identified in several brain regions, indicating abnormal activities occurred in corresponding regions and underlying the cognitive susceptibility to depression. Studies reported that patients with MDD have ALFF and fALFF abnormalities and put forward these abnormalities might be the indicators of brain dysfunction and may be used as reliable imaging markers for patients with MDD. Unbalanced information transfer in a wide range of brain regions is reflected by FC, as is referred in the article. Hence, FC may serve as a neuroimaging marker to investigate the human brain functions including those in patients with MDD.
Furthermore, Dr. Li comments that DTI and MRS can be used in the study of the molecular pathophysiology of different neuropsychiatric disorders, such as MDD, for that they are unique techniques directly detect the movement of water molecules in brain tissue and assess the concentration of various biochemical metabolites in the brain. Alterations of DTI reflect white matter damages and abnormalities of MRS indicate abnormal metabolism in MDD, which may all related to the pathogenesis of MDD.
However, Dr. Li also underlines that many problems are there to be addressed, such as the precise associations between abnormal changes and clinical symptoms, and the correlations between structural and functional changes and the like, and multicenter trials and longitudinal dynamic tracking surveys are needed in the future.
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