Functional Brain Activity Associated With Intermittent Rhythmic Delta/Theta Activity: A Transdiagnostic...

Intermittent rhythmic delta/theta activity (IRDA/IRTA) detected via electroencephalography (EEG) has been implicated in the pathophysiology of neuropsychiatric illnesses. Therefore, a combined EEG and functional magnetic resonance imaging (fMRI) approach was applied in a transdiagnostic group of patients with different causalities, i.e., autoimmune-mediated (in suspected autoimmune psychiatric syndromes [APS]) and primary psychiatric (borderline personality disorder [BPD]) causalities, as well as in healthy control (HC) participants, to characterize the brain regions functionally correlated with IRDA/IRTA.

Overall, 135 EEG-fMRI datasets met the quality criteria, including 33 patients with suspected APS, 59 cases with BPD, and 43 HC participants. fMRI data were obtained using ultrafast MR encephalography and analyzed using AFNI. IRDA/IRTA events were separated from artifacts using independent component analysis and detected algorithmically. Brain regions (clusters) significantly correlated with IRDA/IRTA were first determined in all participants. Clusters occurring across all groups were classified as consensus areas. The groups were also analyzed individually, adding disease- or disorder-specific clusters not overlapping with the consensus areas.

Eleven consensus areas were identified across the 3 groups: 5 of them showed increased activity (Brodmann area [BA] 43-right [r], BA 2-left [l], BA 4-r, BA 18-r, BA 26/29/30-r), and 6 had reduced activity (BA 39-l, BA 10-l, BA 23-l, BA 19-l, BA 10-r, BA 18-l). The APS group showed 5 additional clusters, all with reduced activity (BAs 39-r, 1/3-r, 8-r, 4-l, 21-r). The BPD group showed one further cluster with increased activity (BA 17-l).

In this study, IRDA/IRTA-related brain activity changes across the groups were identified, with excitatory brain activity especially in fronto-centro-temporal brain areas with similarities to the salience network. Additional disease- or disorder-specific changes were discovered in APS and BPD.