Frequency Dependent Changes In The Amplitude Oflow-frequency Fluctuations In Young Patients With Depression

Background:Major depressive disorder(MDD)is one of the most common chronic affective disorders in clinic.Depression is characterized by high prevalence,high recurrence rate,high suicide rate and high disease burden.A large number of studies have shown that there are abnormalities in multi-site brain functional connections in elderly patients with depression.In many studies,the frequency-dependent changes of low-frequency amplitudes(ALFF)of elderly patients with depression have been found.There is also evidence that the resting state BOLD(blood oxygenation level dependent)signal also gradually changes with age,and it is verified that there are differences between early-onset depression and late-onset depression.However,the research on whether there is a frequency-dependent change of low frequency amplitude in young depression patients in our country is still insufficient,and the results are inconsistent.Therefore,more research is needed on pathophysiology and etiology of young depression patients,because it is helpful for early diagnosis and treatment of depression,which will further improve the quality of life of patients.The purpose of this study is to collect ALFF data of young MDD patients in order to detect the amplitude of low frequency oscillation(LFO)in different brain functional regions of young depression patients in different frequency bands,hoping to observe the changes of neurological function in patients with major depression and explore its possible pathogenesis.Methods:Resting-state functional magnetic resonance imaging(R-FMRI)is utilized to measure the amplitude of low-frequency fluctuations(ALFF)in 67 young patients(28.7 ± 9.6 years)with MDD and 39 age(28.12±4.41 years)matched healthycontrols at different frequency bands(slow-5(0.01-0.072 Hz),slow-4(0.027-0.08Hz).In order to explore the difference of ALFF values between groups,SPM5 software was used to analyze the processed data and T-test was carried out on two independent samples.Results:The results show that the ALFF value varies with the group(MDD group and HC group)and frequency band(slow 4 and slow 5 frequency bands).First of all,the main effect of frequency shows that ALFF varies with different frequency bands,with slow-4 > slow-5 mainly in non-cortical areas,such as cingulate gyrus,fusiform gyrus,basal ganglia and midbrain,while slow-5 > slow-4 appears in multiple cortical areas,such as middle temporal gyrus,inferior frontal gyrus and ventromedial frontal gyrus.Then,compared with the control group,we found that the ALFF value of depression patients in The primary somatosensory cortex(S1)decreased,while the ALFF value in the island leaf increased.More importantly,we also found significant interaction between bands and groups in the Dorsal anterior cingulate cortex(dACC),which indicates that the dynamic changes of low frequency amplitude we observed may be related to frequency.We observed significant group and frequency interaction effects on ALFF values in the dorsal anterior cingulate cortex dACC,and there were more significant group differences in the slow-5 band than in the slow-4 band.Limitation:First of all,most patients in this study have received different types of antidepressant therapy(including drugs,psychotherapy,physical therapy,etc.),which may affect the ALFF value of depressive patients.Second,although we require the subjects to keep their eyes closed during the scanning process,we cannot rule out the possibility that some subjects fail to follow this instruction during the whole rest period without being tracked by the subjects or monitored by other monitoring equipment.Third,considering this is a cross-sectional study,the sample size is relatively small,but the age range is wide,the accuracy of the data results may be affected.Fourth,the exact origin and mechanism of ALFF are much more complicated than we expected.The research results in this area are not completely clear at present,and more research and further exploration and clarification are needed in the future.Conclusions:The results of rs-fMRI based on ALFF method in this study show that the changes of ALFF in patients with major depressive disorder exist in various functional regions of the brain,which indicates that the occurrence of the disease involves dysfunction in multiple regions of the brain.This finding may provide insights for understanding the pathophysiology of young depression patients.