Frequency-Specific Changes in the Fractional Amplitude of the Low-Frequency Fluctuations in the Default Mode Network in Medication-Free Patients With Bipolar II Depression: A Longitudinal Functional MRI Study.

Jun Zhou,Xiaogang Chen,Chunwang Li,Zihao Yang,Xiaoqian Ma,Aijun Liao,Ying He,Honghong Ren,Zongchang Li,Jinsong Tang,Jinguang Li

doi:10.3389/fpsyt.2020.574819

Abstract

Objective: This study aimed to examine the treatment-related changes of the fractional amplitude of low-frequency fluctuations (fALFF) in the default mode network (DMN) across different bands after the medication-free patients with bipolar II depression received a 16-week treatment of escitalopram and lithium.Methods: A total of 23 medication-free patients with bipolar II depression and 29 healthy controls (HCs) were recruited. We evaluated the fALFF values of slow 4 (0.027–0.073 Hz) band and slow 5 (0.01–0.027 Hz) band of the patients and compared the results with those of the 29 HCs at baseline. After 16-week treatment of escitalopram with lithium, the slow 4 and slow 5 fALFF values of the patients were assessed and compared with the baselines of patients and HCs. The depressive symptoms of bipolar II depression in patients were assessed with a 17-item Hamilton Depression Rating Scale (HDRS) before and after treatment.Results: Treatment-related effects showed increased slow 5 fALFF in cluster D (bilateral medial superior frontal gyrus, bilateral superior frontal gyrus, right middle frontal gyrus, and bilateral anterior cingulate), cluster E (bilateral precuneus/posterior cingulate, left cuneus), and cluster F (left angular, left middle temporal gyrus, left superior temporal gyrus, and left supramarginal gyrus) in comparison with the baseline of the patients. Moreover, a positive association was found between the increase in slow 5 fALFF values (follow-up value minus the baseline values) in cluster D and the decrease in HDRS scores (baseline HDRS scores minus follow-up HDRS scores) at follow-up, and the same association between the increase in slow 5 fALFF values and the decrease in HDRS scores was found in cluster E.Conclusions: The study reveals that the hypoactivity of slow 5 fALFF in the DMN is related to depression symptoms and might be corrected by the administration of escitalopram with lithium, implying that slow 5 fALFF of the DMN plays a key role in bipolar depression.

Highlights

Depression is the most common manifestation of mood state in bipolar disorder II, which is responsible for high suicide rates [1] and significant functional impairment [2]
Combining our findings and the findings mentioned above, we found that escitalopram and lithium might have an effect on the fractional amplitude of low-frequency fluctuations (fALFF) of the medial prefrontal cortex (mPFC) and depressive symptoms by modulating neurotransmitters, neuronal metabolism, and synaptic plasticity in bipolar II depression
We found that the lower fALFF value in the left inferior parietal lobule (IPL) and left lateral temporal cortex (LTC) can be corrected by escitalopram and lithium

Summary

Introduction

Depression is the most common manifestation of mood state in bipolar disorder II, which is responsible for high suicide rates [1] and significant functional impairment [2]. The amplitude of low-frequency fluctuations (ALFF) is an index of local spontaneous neural activity in the resting state [5, 6] and reflects regional energy metabolism and activity of chemical synaptic signaling in the brain. Treatment-related changes of escitalopram in fALFF were observed in patients with panic disorder [9] and major depression [13], and the changed brain region, including the medial prefrontal cortex (mPFC), was located in the DMN. Treatment-related changes of fALFF within the DMN on bipolar II depression still remain elusive

Methods

Results

Discussion

Conclusion