Time-Frequency Characterization of Resting Brain in Bipolar Disorder during Euthymia—A Preliminary Study

Abstract

The goal of this paper is to investigate the baseline brain activity in euthymic bipolar disorder (BD) patients by comparing it to healthy controls (HC) with the use of a variety of resting state functional magnetic resonance imaging (rs-fMRI) analyses, such as amplitude of low frequency fluctuations (ALFF), fractional ALFF (f/ALFF), ALFF-based functional connectivity (FC), and r egional homogeneity (ReHo). We hypothesize that above-mentioned techniques will differentiate BD from HC indicating dissimilarities between the groups within different brain structures. Forty-two participants divided into two groups of euthymic BD patients (n = 21) and HC (n = 21) underwent rs-fMRI evaluation. Typical band ALFF, slow-4, slow-5, f/ALFF, as well as ReHo indexes were analyzed. Regions with altered ALFF were chosen as ROI for seed-to-voxel analysis of FC. As opposed to HC, BD patients revealed: increased ALFF in left insula; increased slow-5 in left middle temporal pole; increased f/ALFF in left superior frontal gyrus, left superior temporal gyrus, left middle occipital gyrus, right putamen, and bilateral thalamus. There were no significant differences between BD and HC groups in slow-4 band. Compared to HC, the BD group presented higher ReHo values in the left superior medial frontal gyrus and lower ReHo values in the right supplementary motor area. FC analysis revealed significant hyper-connectivity within the BD group between left insula and bilateral middle frontal gyrus, right superior parietal gyrus, right supramarginal gyrus, left inferior parietal gyrus, left cerebellum, and left supplementary motor area. To our best knowledge, this is the first rs-fMRI study combining ReHo, ALFF, f/ALFF, and subdivided frequency bands (slow-4 and slow-5) in euthymic BD patients. ALFF, f/ALFF, slow-5, as well as REHO analysis revealed significant differences between two studied groups. Although results obtained with the above methods enable to identify group-specific brain structures, no overlap between the brain regions was detected. This indicates that combination of foregoing rs-fMRI methods may complement each other, revealing the bigger picture of the complex resting state abnormalities in BD.

Alterations in resting‐state whole‐brain functional connectivity pattern similarity in bipolar disorder patients

“…In our current study, decreased FcHo was revealed in the left MTG. This finding was strongly supported by a growing body of prior neuroimaging studies, which have broadly revealed that BD participants had both morphological and functional abnormalities of left MTG (Chai et al, 2020;Chrobak et al, 2021;Hibar et al, 2018;Liu et al, 2021;Wang et al, 2016). The MTG involves in the processing of numerous complex emotions, cognitions, and behaviors (Xu et al, 2019).…”

Altered frequency-specific/universal amplitude characteristics of spontaneous brain oscillations in patients with bipolar disorder

“… Zhong et al (2019) found that patients with depressed BD had decreased ALFF values in the bilateral PCu/PCC at the slow-4 frequency, as well as decreased ALFF values in the right PCu and increased ALFF values in the right middle occipital gyrus at the slow-5 frequency. Chrobak et al (2021) found that patients with euthymic BD have increased ALFF values in the left middle temporal pole at the slow-5 frequency and comparable ALFF values at the slow-4 frequency. Chang et al (2019) did not distinguish patients’ mood states and found that ALFF values were increased in the striatum, limbic, paralimbic, prefrontal cortex, and temporal gyrus and decreased in the visual cortex at the slow-5 and slow-4 frequencies.…”

Altered Brain Function in Treatment-Resistant and Non-treatment-resistant Depression Patients: A Resting-State Functional Magnetic Resonance Imaging Study

“…ALFF reflects the intensity of spontaneous activity in a region of the brain over a short period of time by calculating the average amplitude of low-frequency oscillations in that region (24). However, the diseases currently studied using a combined ALFF and ReHo approach mainly include Parkinson's disease (26), generalized anxiety disorder (25), bipolar disorder (27), and migraine without aura (28), while differential studies of TRD and nTRD are lacking. So far, there have been some studies on the difference between TRD and nTRD, but most of them use ALFF or ReHo as a single indicator.…”