25 Two of the pathways act to regulate output from frontal cortex to insure appropriate behavioral responses to stimuli.25 The “direct” pathway facilitates thalamic stimulation of the cortex. The “indirect” pathway acts to inhibit the thalamus – thus permitting the cortex to shift sets and respond to novel stimuli. OCD may result from excessive neural tone in the direct pathway Inhibitors,research,lifescience,medical relative to the indirect pathway. Neuroimaging studies of pediatric OCD Below is a brief review
of neuroimaging studies of pediatric OCD. The aim is provide enough background to highlight the move to a translational approach from an investigative one. Reports relevant to the translational research approach are in the following section. Frontal cortex Rosenberg et al31 did not find any significant difference in prefrontal
cortex (PFC) volume between pediatric OCD patients and age- and sex-matched Inhibitors,research,lifescience,medical controls. However, the measurement of total PFC volume may have been too gross a measure, and more subtle abnormalities in specific subregions lost. Indeed, the genu of the corpus callosum, which connects aspects of PFC across the hemispheres, was found to be larger in pediatric OCD subjects.32 Larger anterior cingulate volumes were also noted, consonant Inhibitors,research,lifescience,medical with the larger genu finding.33 Anterior cingulate volume was correlated with OCD symptom severity (r=0.73, obsessive subscale). This was replicated in a second sample.34 This is noteworthy as replication is rare in psychiatric research. Developmentally, the normal increase in anterior cingulate volume with age (r=0.45) was absent in patients with OCD (r=-0.12). Rosenberg and Keshavan33 hypothesized that increased anterior cingulate volumes correlating with reduced basal ganglia volumes (r=-0.46) in pediatric patients with Inhibitors,research,lifescience,medical OCD is
suggestive of neural network dysplasia Inhibitors,research,lifescience,medical – characterized by alterations in postnatal pruning. Developmentally, the greater anterior cingulate volume and lack of a correlation with age in pediatric patients with OCD may reflect delayed or reduced neural pruning, while reduced striatal volume might reflect increased pruning. No differences in posterior cingulate or dorsolateral prefrontal Brefeldin_A cortex (DLPFC) volume were noted.33 Subcortical and other regions Smaller basal ganglia volumes have been reported in treatment-naïve pediatric OCD patients.31 Furthermore, greater ventricular brain ratios have been observed in adolescent patients with OCD compared with healthy controls, which would be expected with decreased basal ganglia volume.35 The thalamus was found to be larger in pediatric OCD patients as compared with controls, a difference that resolved with SSRI learn more treatment36 but not cell differentiation cognitive behavioral therapy37 Also in the thalamus, greater medial but not lateral thalamic choline was observed in pediatric patients with OCD compared with both healthy controls and patients with major depressive disorder (MDD).