2 - (OP17) Adaptive Thalamic Plasticity Induced by Cognitive-behavioral Regulation in OCD: A Multimodal Fmri Investigation

Background: The thalamus serves as a critical hub within the Cortico-Striato-Thalamo-Cortical (CSTC) circuits. However, its dynamic role in the pathophysiology of obsessive-compulsive disorder (OCD) and its response to Cognitive-Behavioral Therapy (CBT) remain to be fully characterized. This study integrated resting-state and task-based fMRI to investigate the functional characteristics of thalamic circuitry and the mechanisms of neural plasticity induced by CBT regulation in the contamination/cleaning subtype of OCD.

Methods: The study was conducted in two phases: (1) Resting-state study: 88 OCD patients and 57 healthy controls (HC) were enrolled to identify baseline functional connectivity (FC) aberrations. (2) Task-based study: Utilizing a clinical trial design, 42 OCD patients were assigned to the CBT-based Emotion Regulation (ER) group, with 14 OCD patients as the Control group and 30 HCs for comparison. A novel, high-ecological validity paradigm was employed to examine changes in thalamo-related FC during cognitive-behavioral regulation (comprising Cognitive Restructuring and Exposure and Response Prevention).

Results: (1) OCD patients exhibited enhanced intra-circuit connectivity within the affective loop and increased inter-circuit connectivity among cognitive, affective, and behavioral loops. Specifically, FC between the orbitofrontal cortex (OFC) and the thalamus was significantly elevated. Correlation analysis revealed that left OFC—left thalamus FC was positively correlated with obsession scores (r = 0.274, p = 0.010); left OFC—right thalamus FC was positively correlated with both obsession scores (r = 0.221, p = 0.038) and BAI anxiety scores (r = 0.177, p = 0.046). (2) Under cognitive-behavioral regulation, the ER group demonstrated significantly higher FC between the thalamus and key nodes—including the nucleus accumbens (NAc), OFC, and ventromedial prefrontal cortex (vmPFC)—compared to the OCD control group. Crucially, these connections in the ER group showed no significant difference from those in the HC group.

Conclusions: The findings demonstrate that OCD is characterized by neural aberrations defined by OFC-thalamic hyperconnectivity within the affective loop, which directly correlates with clinical severity. Furthermore, this study confirms that during the regulation of cognitive-behavioral phenotypes, the thalamus facilitates the adaptive modulation of internal functions within CSTC sub-circuits (particularly the ventral affective and prefrontal-limbic loops). These results provide robust evidence for neural plasticity induced by targeted psychological interventions.