q11 chromsome 22 and Obsessive Compulsive Disorder

“One susceptibility gene when it occurs in a particular form contributes to a man’s risk of developing OCD. [...] The gene carries the instructions to make an enzyme, catechol-O- methyltransferase (COMT), thought to end the action of two chemicals that transmit signals between nerve cells, dopamine and norepinephrine. They are involved in many brain activities, including its control of emotions, particularly rewards and anxiety. [...] In men with OCD, the researchers found, alterations in the comt gene cause a decrease in the production of the COMT enzyme. Consequently, the scientists suggest, the amounts of two neurotransmitters in the synapses increase, possibly because they may not be recycled efficiently, resulting in a biochemical imbalance that contributes to OCD. [...] In Karayiorgou’s previous research, she and her colleagues found that patients with small deletions in a region called q11 of chromosome 22 have a number of psychiatric illnesses, including schizophrenia and OCD.”


Striatial/hippocampal involvement in OCD/Addiction and Spatial Memory

One area of the brain called the striatum helps record cues or landmarks that lead to a familiar destination. It is the area of the commuter’s brain that goes on autopilot and allows people to get to work, often with little memory of the trip. [...] But when driving to an unfamiliar place, the brain recruits a second area called the hippocampus, which is involved in a more flexible system called spatial learning. [...] In one group, they disrupted areas of the striatum in mice and discovered that their ability to complete landmark navigation tasks was impaired. However, these mice actually improved on tasks that involved spatial learning. Conversely, when the researchers disrupted an area of the hippocampus involved in spatial learning, the animals could no longer navigate spatially but learned landmark tasks more quickly. [...] Obsessive-compulsive disorder, Tourette syndrome, and drug addiction involve abnormal function of the striatum.