Distinct Neural Correlates of Washing, Checking, and Hoarding Symptom Dimensions in Obsessive-compulsive Disorder
Mataix-Cols D, Wooderson S, Lawrence N, Brammer MJ, Speckens A and Phillips ML;
Commented by , 28 Jun 2004
Aims of the study
To investigate the neural correlates of three symptom dimensions that have consistently been identified in factor-analytic studies of obsessive-compulsive disorder (OCD): contamination/washing, aggressive/checking, and hoarding.
Method
The neural correlates of washing, checking, and hoarding symptom dimensions were examined within the same subjects, using a symptom provocation paradigm.16 patients with mixed OCD symptoms and 17 healthy volunteers viewed pictures depicting contamination/washing, aggressive/checking, and hoarding material. In addition, both patients and controls were exposed to aversive pictures, unrelated to symptoms of OCD. The neural correlates of the exposures were assessed using functional magnetic resonance imaging (fMRI).
Results
Different types of exposure involved different brain regions:
- In the washing experiment, patients showed greater activations than controls in bilateral ventromedial prefrontal regions and the right caudate nucleus.
- In the checking experiment, patients showed greater activation than controls in the subthalamic region, in the right putamen/globus pallidus and right thalamus, as well as in various dorsolateral cortical regions.
- In the hoarding experiment, patients showed greater activations than controls in left precentral/superior frontal, fusiform, and right orbitofrontal cortex.
- In the aversive, symptom-unrelated experiment, patients showed greater activation than controls only in occipitotemporal regions, suggesting that the findings of the 3 previous experiments were mostly symptom specific.
Discussion
The results suggest that different OCD symptoms may be mediated by distinct neural components of frontostriatothalamic circuits. As such, they give support to the conceptualisation of OCD as a heterogeneous disorder, consisting of several, potentially overlapping clinical syndromes.
Factor and cluster analytic studies have identified several symptom dimensions (ref. 1), that show different patterns of genetic inheritance, response to treatment, and comorbidity. In addition, structural as well as functional brain imaging studies have shown the involvement of different structures and circuits according to different predominant symptoms of OCD.
In particular, the June issue of the American Journal of Psychiatry includes a study by Saxena et al. (ref. 2) on cerebral glucose metabolism in obsessive-compulsive hoarding. OCD patients with mainly hoarding symptoms had a different pattern of cerebral glucose metabolism than nonhoarding OCD patients and normal controls.
The study has a number of limitations. In particular, the authors did not exclude patients with comorbidity (e.g. with depression), they did not compare medicated and unmedicated patients, and the number of subjects investigated was quite small. In spite of these limitations, the results of the investigation represent a major contribution to the current knowledge on OCD with potentially far reaching implications for the management and treatment of the disorder as well as for future research in the field.
References
1. Leckman JF, Grice DE, Boardman J, Zhang A, Vitale A, Bondi C, Alsobrook J, Petersen BS, Cohen DJ, Rasmussen SA, Goodman WK, McDougle CJ, and Pauls DL (1997): Symptoms of obsessive-compulsive disorder. American Journal of Psychiatry, 154: 911-917.
2. Saxena S, Brody AL, Maidment KM, Smith AC, Zohrabi N, Katz E, Baker SK, and Baxter LR (2004): Cerebral Glucose Metabolism in Obsessive–Compulsive Hoarding. American Journal of Psychiatry, 161: 1038-1048.