Functional magnetic resonance imaging study of regional brain activation during implicit sequence learning in obsessive-compulsive disorder.
BACKGROUND
Corticostriatal circuitry has been implicated in the pathophysiology of obsessive-compulsive disorder (OCD). The serial reaction time (SRT) task, a paradigm that tests implicit sequence learning, has been used with imaging to probe striatal function. Initial studies have indicated that OCD patients exhibit deficient striatal activation and aberrant hippocampal recruitment compared with healthy control (HC) subjects. Here, we used the SRT and functional magnetic resonance imaging (fMRI) to replicate prior results in a larger sample and to test for relationships between regional activation and OCD symptom dimensions.


METHODS
Using SPM99, fMRI-SRT data from 12 OCD and 12 matched HC subjects were analyzed. Symptom dimensions followed a four-factor model scored on a 0- to 10-point scale.


RESULTS
For the implicit learning versus random contrast, group by condition interactions revealed aberrant recruitment within the hippocampus as well as orbitofrontal cortex (OCD > HC) but no striatal group differences. However, an inverse correlation was found between striatal activation and specific symptom factors.


CONCLUSIONS
These results replicate previous smaller studies showing aberrant hippocampal recruitment in OCD during SRT performance. Although findings of deficient striatal activation in OCD were not replicated, correlation results suggest that this inconsistency may be attributable to differences among OCD symptom dimensions.
Department of Psychiatry, Massachusetts General Hospital & Harvard Medical School, Boston, Massachusetts 02129, USA. rauch@psych.mgh.harvard.edu
Scott L
SL
Rauch
Michelle M
MM
Wedig
Christopher I
CI
Wright
Brian
B
Martis
Katherine G
KG
McMullin
Lisa M
LM
Shin
Paul A
PA
Cannistraro
Sabine
S
Wilhelm
D000328:Adult; D001921:Brain / Q000503:physiopathology*; D002540:Cerebral Cortex / Q000503:physiopathology; D015331:Cohort Studies; D005260:Female; D006624:Hippocampus / Q000503:physiopathology; D006801:Humans; D007858:Learning / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D017072:Neostriatum / Q000503:physiopathology; D009434:Neural Pathways / Q000503:physiopathology; D009771:Obsessive-Compulsive Disorder / Q000503:physiopathology* / Q000523:psychology*; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D011999:Recruitment, Neurophysiological