ABSTRACT
BACKGROUND: Although repeatedly associated with white matter microstructural alterations, bipolar disorder (BD) has been relatively unexplored using complex network analysis. This method combines structural and diffusion magnetic resonance imaging (MRI) to model the brain as a network and evaluate its topological properties. A group of highly interconnected high-density structures, termed the 'rich-club', represents an important network for integration of brain functioning. This study aimed to assess structural and rich-club connectivity properties in BD through graph theory analyses. METHOD: We obtained structural and diffusion MRI scans from 42 euthymic patients with BD type I and 43 age- and gender-matched healthy volunteers. Weighted fractional anisotropy connections mapped between cortical and subcortical structures defined the neuroanatomical networks. Next, we examined between-group differences in features of graph properties and sub-networks. RESULTS: Patients exhibited significantly reduced clustering coefficient and global efficiency, compared with controls globally and regionally in frontal and occipital regions. Additionally, patients displayed weaker sub-network connectivity in distributed regions. Rich-club analysis revealed subtly reduced density in patients, which did not withstand multiple comparison correction. However, hub identification in most participants indicated differentially affected rich-club membership in the BD group, with two hubs absent when compared with controls, namely the superior frontal gyrus and thalamus. CONCLUSIONS: This graph theory analysis presents a thorough investigation of topological features of connectivity in euthymic BD. Abnormalities of global and local measures and network components provide further neuroanatomically specific evidence for distributed dysconnectivity as a trait feature of BD.
Subject(s)
Bipolar Disorder/diagnostic imaging , Brain/diagnostic imaging , Magnetic Resonance Imaging/methods , Nerve Net/diagnostic imaging , Adult , Diffusion Magnetic Resonance Imaging/methods , Female , Humans , Male , Middle AgedABSTRACT
BACKGROUND: A section of the UMCG Child and Adolescent Psychiatry Department is currently focusing much of its research on tic disorders. AIM: To provide an overview of the research projects on tic disorders being currently undertaken at our center. METHOD: We discuss our research projects giving particular attention to factors that are restricting current research. RESULTS: The first project is TIC Genetics, a project involving international collaboration. The researchers are looking for rare genetic variants in several family members who have tics and for new gene mutations in children who have tics but no family history of tics. TIC Genetics also investigates the interactions between genes and the environment. A second large-scale longitudinal project, the European Multicentre Tics in Children Study (EMTICS), is focusing on the interplay between genetics, auto-immunity, and environmental factors as a possible cause for the onset and exacerbation of tics. Finally, TS-EUROTRAIN is a European collaboration that concentrates on genetics, neuro-imaging and animal models. CONCLUSION: International collaborations are essential if we are to acquire a deeper understanding of the etiology of tic disorders.
