The CORTICO-STRIATAL-THALAMO-CORTICAL (CSTC) circuit in the brain has an important role in controlling movement and thought. As a consequence, any dysfunction in this circuit may cause movement and psychological disorders. For example, one hypothesis to explain Obsessive Compulsive Disorder (OCD) is that alteration in this circuit causes a positive feedback loop (direct pathway) to become strengthened and a negative feedback loop (indirect pathway) to become weakened, which causes hyperactivity in the cerebral cortex resulting in OCD symptoms. We have designed and simulated a biomimetic electronic circuit with a Carbon Nanotube synaptic layer and CMOS neurons that mimics the CSTC loop in healthy and OCD conditions. This circuit simulation demonstrates the utility of neuromorphic circuits in brain modeling, since varied behavior can be demonstrated via modification of synaptic strengths. We further demonstrate the role noise (variability) plays in the CSTC circuit function and dysfunction and describe a noise-generating circuit implementation to inject noise into neuromorphic circuits based on photons emitted by an LED.