Tracking Disordered Brain Dynamics in Psychiatry

The brain’s distributed patterns of activity give rise to a rich tapestry of dynamics that underpin individuals’ transitions through different cognitive states. In neuroimaging, the trajectory of these dynamics is often studied in terms of switches between specific brain states ( 1 Lurie D.J. Kessler D. Bassett D.S. Betzel R.F. Breakspear M. Kheilholz S. et al. Questions and controversies in the study of time-varying functional connectivity in resting fMRI. Netw Neurosci. 2020; 4: 30-69 Crossref PubMed Scopus (230) Google Scholar ); researchers typically examine how long individuals remain in a specific state (dwell time) and the probability of switching from one state to another (transition probability), as well as how these properties vary across individuals. In neuropsychiatry, such analyses have characterized disordered brain dynamics in schizophrenia (SCZ) and bipolar disorder (BD). However, in the current issue of Biological Psychiatry, Ye et al. ( 2 Ye J. Sun H. Gao S. Dadashkarimi J. Rosenblatt M. Rodriguez R.X. et al. Altered brain dynamics across bipolar disorder and schizophrenia during rest and task switching revealed by overlapping brain states. Biol Psychiatry. 2023; 94: 580-590 Abstract Full Text Full Text PDF Scopus (1) Google Scholar ) point out that the results of these studies have been equivocal, showing a mixture of increases and decreases, as well as no difference in dwell time or transition probability. Ye et al. argue that these discrepancies may be underpinned by the field’s prevailing tendency to use a winner-takes-all approach to state definition, where a single time point of neural activity is assigned exclusively to one representative brain state to model transitions. To overcome this limitation, Ye et al. present a novel pipeline for analyzing state transitions that allows for each time point of neural data to be jointly explained by multiple representative brain states. This approach allows the authors to characterize the relative contribution of different patterns of brain activity to subjects’ resting-state dynamics. SEE CORRESPONDING ARTICLE ON PAGE 580 SEE CORRESPONDING ARTICLE ON PAGE 580 Altered Brain Dynamics Across Bipolar Disorder and Schizophrenia During Rest and Task Switching Revealed by Overlapping Brain StatesBiological PsychiatryVol. 94Issue 7PreviewIndividuals with bipolar disorder (BD) and schizophrenia (SCZ) show aberrant brain dynamics (i.e., altered recruitment or traversal through different brain states over time). Existing investigations of brain dynamics typically assume that one dominant brain state characterizes each time point. However, as multiple brain states likely are engaged at any given moment, this approach can obscure alterations in less prominent but critical brain states. Here, we examined brain dynamics in BD and SCZ by implementing a novel framework that simultaneously assessed the engagement of multiple brain states. Full-Text PDF Open Access