Fronto-cingulate effective connectivity in obsessive compulsive disorder: a study with fMRI and dynamic causal modeling

Abstract

Evidence suggests that obsessive compulsive disorder (OCD) is associated with an overactive error control system. A key role in error detection and control has been ascribed to the fronto-cingulate system. However, the exact functional interplay between the single components of this network in OCD is largely unknown. Therefore, the present study combined a univariate data analysis and effective connectivity analysis using dynamic causal modeling (DCM) to examine error control in 21 patients with OCD and 21 matched healthy controls. All subjects performed an adapted version of the Stroop color-word task while undergoing fMRI scans. Enhanced activation in the fronto-cingulate system could be detected in OCD patients during the incongruent task condition. Additionally, task-related modulation of effective connectivity from the dorsal ACC to left DLPFC was significantly stronger in OCD patients. These findings are consistent with an overactive error control system in OCD subserving suppression of prepotent responses during decision-making.

Figure 1

Alternative models for connections considered during model selection: (a) Model 01 with intrinsic connections between left DLPFC and dorsal ACC; (b) Model 02 with intrinsic connections between right DLPFC and dorsal ACC; (c) Model 03 with intrinsic connections between dorsal ACC and both left and right DLPFC; (d) Model 04 with, in addition to Model 03, intrinsic connections between dorsal ACC and rostral ACC; (e) Model 05 with, in addition to Model 04, direct interhemispheric intrinsic connections between left and right DLPFC. Displayed are in (e) also the bilinear interaction terms as the result of a second model selection process which was performed analogous to the intrinsic model selection procedure (corresponding to Model 05.5).

Figure 2

Significant areas for (a) main effects of task (incongruent > congruent condition; P < 0.05, FWE corrected) and (b) main effect of group (OCD patients > healthy controls, P < 0.001, k = 12 voxels).

Figure 3

Significant areas for (a) task by group interaction effects (OCD patients > healthy controls for incongruent versus congruent condition) (P < 0.001, k = 12 voxels) and (b) increased activation in OCD patients compared to controls for the incongruent condition only (P < 0.001, k = 12 voxels).

Figure 4

Areas of significant correlations between Stroop interference scores and activation during the incongruent task condition for (a) OCD patients and (b) healthy controls (P < 0.001, k = 12 voxels).

Figure 5

(a) Overview of pathways showing a significant task effect with higher connectivity parameters in the incongruent as compared to the congruent condition (P < 0.05, corrected, in blue) and a significant group, task and task by group interaction effect (P < 0.05, in red) where connectivity parameters were significantly higher for the incongruent condition in OCD patients relative to healthy controls. (b) Marginal means for the dorsal ACC to left DLPFC connectivity (patients versus controls, incongruent versus congruent condition) showing predominant and significant difference in connectivity parameters for the incongruent condition with OCD patients > controls (P < 0.01).