Default Mode Network across dx
"The resting state brain networks, particularly the Default Mode Network (DMN), have been found to be altered in several psychopathological conditions such as depression and anxiety. In this study we hypothesized that cortical areas of the DMN, particularly the anterior regions--medial prefrontal cortex and anterior cingulate cortex--would show an increased functional connectivity associated with both anxiety and depression. Twenty-four healthy participants were assessed using Hamilton Depression and Anxiety Rating Scales and completed a resting-state functional magnetic resonance imaging scan. Multiple regression was performed in order to identify which areas of the DMN were associated with anxiety and depression scores. We found that the functional connectivity of the anterior portions of DMN, involved in self-referential and emotional processes, was positively correlated with anxiety and depression scores, whereas posterior areas of the DMN, involved in episodic memory and perceptual processing were negatively correlated with anxiety and depression scores. The dissociation between anterior and posterior cortical midline regions, raises the possibility of a functional specialization within the DMN in terms of self-referential tasks and contributes to the understanding of the cognitive and affective alterations in depressive and anxiety states."
Default mode network dissociation in depressive and anxiety states - PubMed (nih.gov)
"The default mode network (DMN) is suggested to play a pivotal role in schizophrenia; however, the dissociation pattern of functional connectivity of DMN subsystems remains uncharacterized in this disease. In this study, resting-state fMRI data were acquired from 55 schizophrenic patients and 53 matched healthy controls. DMN connectivity was estimated from time courses of independent components. The lateral DMN exhibited decreased connectivity with the unimodal sensorimotor cortex but increased connectivity with the heteromodal association areas in schizophrenics. The increased connectivity between the lateral DMN and right control network was significantly correlated with negative and anergia factor scores in the schizophrenic patients. The anterior and posterior DMNs exhibited increased and decreased connectivity with the right control and lateral visual networks, respectively, in schizophrenics. The altered DMN connectivity may underlie the hallucinations, delusions, thought disturbances, and negative symptoms involved in schizophrenia. Furthermore, DMN connectivity patterns could be used to differentiate patients from controls with 76.9% accuracy. These findings may shed new light on the distinct role of DMN subsystems in schizophrenia, thereby furthering our understanding of the pathophysiology of schizophrenia. Elucidating key disease-related DMN subsystems is critical for identifying treatment targets and aiding in the clinical diagnosis and development of treatment strategies."
"This study found a dissociative pattern of NH in the DMN (increased NH in the left superior MPFC and decreased NH in the right PCC and bilateral precuneus) in patients with BD. NH abnormalities in the left superior MPFC, right PCC, and bilateral precuneus could be associated with emotional and cognitive dysfunction in the DMN. In addition, NH value in the left superior MPFC can serve as a potential marker to distinguish patients with BD from the healthy. Our study is the first to explore the connection between dyslipidemia and brain function in patients with BD and provide preliminary evidence that dyslipidemia could be related to abnormal DMN connections in BD. In future studies, larger sample size with a longitudinal study design should be considered to explore the possibility of blood lipid level as a marker for identifying brain abnormalities at different stages of BD."
"Sleep deprivation (SD) can alter extrinsic, task-related fMRI signal involved in attention, memory and executive function. However, its effects on intrinsic low-frequency connectivity within the Default Mode Network (DMN) and its related anti-correlated network (ACN) have not been well characterized. We investigated the effect of SD on functional connectivity within the DMN, and on DMN-ACN anti-correlation, both during the resting state and during performance of a visual attention task (VAT). 26 healthy participants underwent fMRI twice: once after a normal night of sleep in rested wakefulness (RW) and once following approximately 24h of total SD. A seed-based approach was used to examine pairwise correlations of low-frequency fMRI signal across different nodes in each state. SD was associated with significant selective reductions in DMN functional connectivity and DMN-ACN anti-correlation. This was congruent across resting state and VAT analyses, suggesting that SD induces a robust alteration in the intrinsic connectivity within and between these networks."
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Conclusion
Dissociative symptoms appear to have a significant impact on affective-cognitive functioning in BPD and should be taken into account in future research and therapy, even when not being the major focus. While the precise neural mechanisms of dissociation remain elusive, there is evidence for reduced activity in limbic(-related) temporal areas (amygdala, superior temporal gyrus, fusiform gyrus), increased frontal activity (inferior frontal gyrus, dlPFC), and altered interactions between these regions. More research with larger sample sizes and clinical control groups, combining different neuroimaging techniques (e.g., resting-state and task-related fMRI) with clinical measures and behavioral tasks, is needed to improve the understanding of dissociation in BPD."
Research in Dissociative Identity Disorder (DID)
There is some evidence that the aforementioned neurobiological alterations may not be specific to a specific disorder but rather represent a trans-diagnostic phenomenon related to dissociation. Recent findings in DID [90•, 91•] resemble findings for D-PTSD, albeit intra-individual differences (instead of inter-individual differences) were observed: neurobiological responses significantly differed depending on whether DID patients were in a “hyper-aroused traumatic identity state” (with voluntary access to traumatic memories) or in their “normal dissociative identity state” (characterized by dissociative amnesia) [90•, 91•]. In the two studies by Reinders and colleagues (2006, 2014), DID patients showed elevated cardiovascular responses (heart rate and blood pressure) and stronger amygdala and insula activity, along with lower activity in cingulate gyrus, parietal cortex, and parahippocampus when exposed to a trauma script (versus neutral script) while being in their “hyper-aroused traumatic identity state” than in their neutral “hypo-aroused identity state” [90•, 91•]. In another study, DID patients exhibited increased perfusion in bilateral thalamus while being in their (apparently) “normal” state of identity compared to an (apparently) “emotional” identity state [92•]. More research is needed to clarify whether brain activity patterns may differ dependent on states (in the same individuals) or represent stable inter-individual differences, which may allow for a discrimination between diagnostic subgroups/categories [10]."
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