Brain activation of patients with obsessive-compulsive disorder during neuropsychological and symptom provocation tasks before and after symptom improvement: a functional magnetic resonance imaging study
Nakao T, Nakagawa A, Yoshiura T, Nakatani E, Nabeyama M, Yoshizato C, Kudoh A, et al.;
Commented by , 25 Apr 2005
Considerable advances have been made in recent years on brain activity, neuropsychological functioning, and treatment, both pharmacological and psychosocial, in obsessive-compulsive disorder (OCD).
Aims of the study
To confirm abnormalities identified in previous neuroimaging or neuropsychological studies of OCD and to investigate changes in these abnormalities following symptom improvement after treatment.
Brain activation was initiated using a symptom provocation task (generation of words related to obsessive preoccupations with contamination, doubt, and violence) as well as a neuropsychological task (administration of a Chinese character version of the Stroop test). Local brain activation was investigated using functional magnetic resonance imaging (fMRI) before and after treatment, either pharmacological (fluvoxamine) or psychosocial (cognitive-behavioural psychotherapy).
After symptom improvement, patients showed significant differences in brain activation during both tasks:
- Symptom-provocation task: a decreased activation in frontal regions compared with pre-treatment activation
- Stroop task: a generally increased activation in posterior regions compared with pre-treatment activation
Professor Pull's comments
The pathophysiology of OCD has been investigated in a number of studies using functional neuroimagery and neuropsychological assessment procedures.
fMRI is a powerful tool to explore the pathophysiology of OCD. Abnormalities identified by neuroimaging studies include hyperactivity in the prefrontal cortex (PFC) and in the anterior cingulate cortex (ACC). Although studies have yielded conflicting results up to now, there still seems to be considerable consensus with regard to the involvement of the prefrontal cortex-basal ganglia circuits in the pathophysiology of the disorder.
Neuropsychological assessment has become a major tool to explore cognitive functioning in OCD. Abnormalities identified by neuropsychological assessments include various types of cognitive dysfunctions, with regard to, among others, dysfunctions in the areas of executive functioning (including action-monitoring), visuo-spatial processing, and motor speed.
The study described above has many limitations. In particular, it has been done on a very small number of patients (10), and the only cognitive function explored during brain activation was action-monitoring (using only one instrument, i.e., the Stroop test).
On the other side, it is a fascinating report, in that it illustrates, in a quite remarkable way, different major avenues of research, involving both neuroimagery techniques and neuropsychologial assessment procedures, that can be pursued by now in the study of OCD.
First, the study demonstrates how the circuits that are probably involved directly in the pathophysiology of OCD can be explored using brain activation under symptom-provocation.
Second, the study illustrates how the same circuits, as well as additional circuits, possibly involved indirectly in the pathophysiology of the disorder, can be explored through brain activation during various neuropsychological tasks.
Third, the study demonstrates that treatment response, whether after pharmacological or after psychosocial treatment, translates into changes in brain activation, with in particular a reversal of activation in the prefrontal cortex.