Shared and specific neurobiology in bipolar disorder and unipolar disorder: Evidence based on the connectome gradient and a transcriptome-connectome association study

Transcriptional characteristics of human brain alterations in major depressive disorder: A systematic review

Many patients with major depressive disorder (MDD) experience limited treatment effectiveness due to an incomplete understanding of its neurobiological underpinnings. This review integrates neuroimaging and genetic data to examine structural and functional brain changes in MDD, alongside their genetic bases. A PRISMA-guided systematic review of imaging transcriptomics over the past decade was conducted using PubMed and Web of Science. Studies included MRI scans of both MDD patients and healthy controls, as well as brain-wide gene expression data, excluding those that were purely meta-analytical, lacked spatial correlations, or involved transdiagnostic analyses. Of the 206 studies reviewed, 20 met the inclusion criteria. Consistent patterns across studies reveal that key biological processes-such as synaptic signaling, calcium ion binding, neurodevelopment, immune regulation, and neurotransmitter transport-play a central role in brain alterations associated with MDD. Additionally, our findings suggest that electroconvulsive therapy (ECT) may alleviate symptoms by modulating these shared pathways. This review underscores the link between brain changes in MDD and specific gene expression profiles, offering insights that could inform more targeted therapeutic approaches.

Mapping striatal functional gradients and associated gene expression in Parkinson's disease with continuous cognitive impairment

Cognitive impairment in Parkinson's disease is closely tied to striatal dysfunction, yet the neurobiological interface between macroscale connectivity and molecular signatures remains unexplored. This study characterizes striatal gradient organization and its genetic underpinnings across PD cognitive trajectories. We analyzed functional connectivity gradients in 126 PD patients (spanning the cognitive spectrum from normal cognition to dementia) and 40 healthy controls, correlating spatial patterns with neurotransmitter architecture and transcriptomic profiles. Three distinct striatal gradients emerged: Gradient 1 remains stable throughout disease progression and partially aligns with canonical striatal subdivisions. Gradient 2 represents a spatial continuum closely linked to dopaminergic innervation and becomes most pronounced in the dementia stage. Gradient 3 corresponds to cortico-striatal connectivity patterns implicated in both early and advanced cognitive deficits. Spatial transcriptomic and neuroimaging correlation analyses identified significant associations between cortico-striatal gradient disruptions and specific gene expression patterns. These findings provide valuable insights into striatal macro- and microstructural changes in PD and their role in cognitive impairment.

Common and disease-specific patterns of functional connectivity and topology alterations across unipolar and bipolar disorder during depressive episodes: a transdiagnostic study

Bipolar disorder (BD) and unipolar depression (UD) are defined as distinct diagnostic categories. However, due to some common clinical and pathophysiological features, it is a clinical challenge to distinguish them, especially in the early stages of BD. This study aimed to explore the common and disease-specific connectivity patterns in BD and UD. This study was constructed over 181 BD, 265 UD and 204 healthy controls. In addition, an independent group of 90 patients initially diagnosed with major depressive disorder at the baseline and then transferred to BD with the episodes of mania/hypomania during follow-up, was identified as initial depressive episode BD (IDE-BD). All participants completed resting-state functional magnetic resonance imaging (R-fMRI) at recruitment. Both network-based analysis and graph theory analysis were applied. Both BD and UD showed decreased functional connectivity (FC) in the whole brain network. The shared aberrant network across groups of patients with depressive episode (BD, IDE-BD and UD) mainly involves the visual network (VN), somatomotor networks (SMN) and default mode network (DMN). Analysis of the topological properties over the three networks showed that decreased clustering coefficient was found in BD, IDE-BD and UD, however, decreased shortest path length and increased global efficiency were only found in BD and IDE-BD but not in UD. The study indicate that VN, SMN, and DMN, which involve stimuli reception and abstraction, emotion processing, and guiding external movements, are common abnormalities in affective disorders. The network separation dysfunction in these networks is shared by BD and UD, however, the network integration dysfunction is specific to BD. The aberrant network integration functions in BD and IDE-BD might be valuable diagnostic biomarkers.

Motor Functional Hierarchical Organization of Cerebrum and Its Underlying Genetic Architecture in Parkinson's Disease

Hierarchy has been identified as a principle underlying the organization of human brain networks. However, it remains unclear how the network hierarchy is disrupted in Parkinson's disease (PD) motor symptoms and how it is modulated by the underlying genetic architecture. The aim of this study was to explore alterations in the motor functional hierarchical organization of the cerebrum and their underlying genetic mechanism. In this study, the brain network hierarchy of each group was described through a connectome gradient analysis among 68 healthy controls (HC), 70 postural instability and gait difficulty (PIGD) subtype, and 69 tremor-dominant (TD) subtype, including both male and female participants, according to its motor symptoms. Furthermore, transcription-neuroimaging association analyses using gene expression data from Allen Human Brain Atlas and case-control gradient differences were performed to identify genes associated with gradient alterations. Different PD motor subtypes exhibited contracted principal and secondary functional gradients relative to HC. The identified genes in different PD motor subtypes enriched for shared biological processes like metal ion transport and inorganic ion transmembrane transport. In addition, these genes were overexpressed in Ntsr+ neurons cell, enriched in extensive cortical regions and wide developmental time windows. Aberrant cerebral functional gradients in PD-related motor symptoms have been detected, and the motor-disturbed genes have shared biological functions. The present findings may contribute to a more comprehensive understanding of the molecular mechanisms underlying hierarchical alterations in PD.

Comparison of Immune and Systemic Inflammation Parameters in Patients with a Depressive Episode in Bipolar Disorder and Major Depressive Disorder: A Scoping Review

BACKGROUND

Many studies have aimed to investigate and compare immune system and systemic inflammation parameters in patients with bipolar disorder (BD) and major depressive disorder (MDD) suffering from a depressive episode. However, no systematic review of the results has been conducted so far.

AIM

The aim of this study was to conduct a scoping review of research studies comparing immune and systemic inflammation parameters in patients with BD and MDD during a depressive episode.

METHODS

The search for studies was conducted in the Medline and eLIBRARY databases for the period from January 1994 to December 2022. Open-access articles written in English and Russian were selected. The review included original studies that compared groups of patients with BD and MDD (diagnosed based on the DSM-IV, DSM-5, or ICD-10 criterion) by immune and systemic inflammation parameters (such as the counts, ratio, and functions of blood cells, erythrocyte sedimentation rate, concentrations of immunoglobulins, cytokines, acute phase proteins, complement components, and autoantibodies).

RESULTS

The review included 24 studies. Current depressive episodes in patients with BD were associated with higher concentrations of chemokines (C-C motif chemokine ligand 3 (CCL3), CCL4, CCL5, CCL11), platelet-derived growth factor B, and interleukin 9 (IL-9) (two studies in each case), whereas patients with MDD tended to have higher concentrations of soluble tumor necrosis factor receptor 1 and immunoglobulin G to oxidized low-density lipoproteins (two studies each). Patients with BD and MDD had comparable concentrations of IL-8 (five studies); IL-2 and IL-10 (four studies each); IL-13 and gamma interferon (three studies each); IL-17, IL-1Rα, the vascular endothelial growth factor, as well as white blood cells, monocyte, and platelet counts (two studies each). Contradictory results were obtained for the levels of tumor necrosis factor-α (the concentrations did not differ in five studies, were elevated in BD patients in five studies, were elevated in MDD patients in two studies), IL-6 (the concentrations did not differ in eight studies and were elevated in BD patients in four studies), C-reactive protein (the concentrations did not differ in six studies, were elevated in BD patients in two studies), IL-4 (the concentrations did not differ in three studies and were elevated in MDD patients in two studies), IL-1β and the neutrophil count (the levels did not differ in one study each and were elevated in BD patients in two studies). Several studies have demonstrated an association between immune and systemic inflammation parameters and the severity of depressive and anxiety symptoms, melancholic depression, age of mood disorder onset, body mass index, and imipramine equivalent.

CONCLUSION

Some immune and systemic inflammation parameters are associated with a current depressive episode in patients with MDD or BD. These parameters may be considered as potential biomarkers for a differential diagnosis of these disorders.

Treatment outcomes in tinnitus patients are associated with brain functional network: Evidence from connectome gradient and gene expression analysis

The neuroimaging mechanisms underlying differences in the outcomes of sound therapy for tinnitus patients remain unclear. We hypothesize that abnormal hierarchical architecture is the neuro-biomarker for treatment outcome explanation. We conducted functional connectome gradient analyses on resting-state functional MRI images that acquired before intervention to investigate differences among the patients with effective treatment (ET, n = 27), ineffective treatment (IT, n = 41), and healthy controls (HC, n = 59). General linear models were used to analyze the associations between intergroup differential regions and clinical characteristics. Partial least squares regression was employed to reveal correlations with gene expression. Compared to HC, both ET and IT groups displayed significant differences in the default mode network. Moreover, the ET group exhibited wider gradient range and greater gradient variance. Also, the gradient scores of the differential regions between the ET and HC groups were significantly correlated with Self-rating Anxiety Scale and Self-rating Depression Scale scores, and exhibited positive correlations with the transcriptional profiles of genes related to depression and anxiety. Our results indicated that the abnormalities of ET group, may be more relevant to psychiatric disorders, bringing a higher possible therapeutic potential due to the plasticity of the nervous system. Connectome gradient dysfunction with genetic evidence may serve as an indicator for identifying diverse treatment outcomes of the sound therapy for tinnitus patients before treatment.