Abstract task sequence initiation deficit dissociates anxiety disorders from obsessive-compulsive disorder and healthy controls.

In everyday life, humans perform sequences of tasks. These tasks may be disrupted in people with obsessive-compulsive disorder (OCD). Symptoms, such as compulsions, can be considered sequential and often cause repetitions of tasks that disrupt daily living (e.g., checking the stove while cooking). Motor sequences have been used to study behavioral deficits in OCD. However, not all sequences are motor sequences. Some are more "abstract" in that they are composed of a series of tasks (e.g., chopping and stirring) rather than being dependent on individual actions or stimuli. These abstract task sequences require cognitive control mechanisms for their execution. Although theory has proposed deficits in these sequences in OCD as well, they have not been directly investigated. We tested the hypotheses that OCD participants exhibit deficits in the control mechanisms specific to abstract task sequences and more general flexible behavior (measured with task switching within the sequences), relative to health controls (HCs) and clinical controls (participants with anxiety disorders [ANX]). A total of 112 participants completed abstract task sequences consisting of simple categorization tasks. Surprisingly, participants with OCD did not perform worse than HCs or ANX. However, ANX participants showed impairments specific to sequential control that did not extend to more general flexible control. Thus, we showed a novel behavioral dissociation between OCD and ANX specific to abstract task sequential control. These results also implicate deficits in specific frontal sequential control neural circuitry in ANX and not in OCD, where implicit sequential deficits may more closely align with striatal circuits.