Obsessive-compulsive disorder (OCD) is clinically heterogeneous, yet
most previous functional neuroimaging studies grouped together patients with
mixed symptoms, thus potentially reducing the power and obscuring the findings
of such studies.
To investigate the neural correlates of washing, checking, and hoarding
symptom dimensions in OCD.
Symptom provocation paradigm, functional magnetic resonance imaging,
block design, and nonparametric brain mapping analyses.
Sixteen patients with OCD (11 inpatients, 5 outpatients) with mixed
symptoms and 17 healthy volunteers of both sexes.
All subjects participated in 4 functional magnetic resonance imaging
experiments. They were scanned while viewing alternating blocks of emotional
(washing-related, checking-related, hoarding-related, or aversive, symptom-unrelated)
and neutral pictures, and imagining scenarios related to the content of each
Main Outcome Measure
Blood oxygenation level–dependent response.
Both patients and control subjects experienced increased subjective
anxiety during symptom provocation (patients significantly more so) and activated
neural regions previously linked to OCD. Analyses of covariance, controlling
for depression, showed a distinct pattern of activation associated with each
symptom dimension. Patients demonstrated significantly greater activation
than controls in bilateral ventromedial prefrontal regions and right caudate
nucleus (washing); putamen/globus pallidus, thalamus, and dorsal cortical
areas (checking); left precentral gyrus and right orbitofrontal cortex (hoarding);
and left occipitotemporal regions (aversive, symptom-unrelated). These results
were further supported by correlation analyses within patients, which showed
highly specific positive associations between subjective anxiety, questionnaire
scores, and neural response in each experiment. There were no consistently
significant differences between patients with (n = 9) and without (n = 7)
The findings suggest that different obsessive-compulsive symptom dimensions
are mediated by relatively distinct components of frontostriatothalamic circuits
implicated in cognitive and emotion processing. Obsessive-compulsive disorder
may be best conceptualized as a spectrum of multiple, potentially overlapping
syndromes rather than a unitary nosologic entity.