The biology of overactive frontal-striatal circuits is at the center of many behavioral disorders - including, but not limited to: obsessive compulsive disorder, Autism and Aspergers, ADD and ADHD, Parkinson's disease, Huntington's disease, and Tourettes. These pathways seem to be important both for the perceptual processing (what do you attend to) and behavior (what you actually do).
In these subjects with OCD, frontal-striatal circuits are overactive even when correctly rejecting a signal (the Go vs No-Go task)- a visual correlate to the feeling "something's just not right", and then the vicious cycle of obsession. Interestingly, cognitive therapy involving OCD patients being allowed to view their own fMRI scans appear to work when patients could 'see' that their brains were feeding them false signals. For more reading on this check out the book The Mind and the Brain
Obsessive Compulsive Disorder and fMRI