Resting-state brain dynamics characteristics in obsessive-compulsive disorder: A study based on hidden Markov model.

Although previous resting-state fMRI studies have revealed functional abnormalities in multiple brain regions of obsessive-compulsive disorder (OCD) patients, the underlying pathological mechanisms remain unclear. As the brain constitutes a complex dynamic system, capturing its dynamic features could advance our understanding of neural activity mechanisms. This study employed hidden Markov modeling (HMM) to investigate dynamic alterations in resting-state brain activity among OCD patients, offering a dynamic perspective on the disorder's pathophysiology. A total of 60 OCD patients and 57 healthy controls (HCs) were enrolled. The HMM was used to identify distinct brain states, characterizing their activation patterns. Temporal features of these states and differences in transition patterns between states were compared between the two groups. Compared to HCs, OCD patients spent significantly more time in the state characterized by mildly elevated global activation (p = 0.024, partial η2 = 0.070), while spending less time in the state characterized by high activation level in the auditory network (AUD) and salience network (SN), coupled with low activation level in default mode network (DMN) and frontoparietal network (FPN) (p = 0.030, partial η2 = 0.057). Additionally, OCD patients showed decreased switching rate (p = 0.025, partial η2 = 0.044) and particular difficulty transitioning from States 1, 2, and 5 into the state characterized by high SN and low DMN activation. These findings suggest altered dynamic patterns of brain network activity in OCD, characterized by abnormal temporal occupancy of specific brain states and reduced switching between states. These alterations may be related to salience network dysfunction and could contribute to our understanding of cognitive inflexibility in OCD from a dynamic perspective. However, further studies are needed to establish the specificity and clinical relevance of these findings.