Brain Lock: Free Yourself From Obsessive-Compulsive Behavior by Jeffrey M. Schwartz, Beverly Beyette Page A

in the cortex to devise strategies to sign their names, since the automatic transmission and filter were broken. They told us it took thought and effort and was hard work. Before the onset of their disease, they could sign their names without giving it a thought. Now, they actually had to control their hands—physically and mentally. They had to use the cortex to take over a function the striatum would normally have been performing. In people with Huntington’s disease, the striatum ultimately disappears, for all intents and purposes, and the abnormal, foreign movements characteristic of their disease, such as writhing and twisting, increase.
    Whereas in persons with Huntington’s disease the fact that the automatic transmission and filter are broken causes unwanted movements, in persons with OCD it causes unwanted thoughts and urges, called obsessive thoughts and compulsive urges. Just as the subjects with Huntington’s disease had to apply thought and effort to sign their names because the striatum’s automatic transmission and filtering system were broken, people with OCD have to apply thought and effort when doing behavior therapy to work around the intrusive OCD symptoms. With the automatic screening system of the striatum not working properly, effort must be made to change behaviors while the disturbing thoughts and urges are still there. (You’ll learn more about this process in the next chapter.) But there is one big difference: OCD is largely a fixable problem; at the present time, Huntington’s disease unfortunately isnot, although active research is going on, and there is much hope for progress.
    This experiment with people with Huntington’s disease taught us much about the brains of people with OCD. We know that when the striatum is working properly, it acts as a filter, “gating” the sensory information sent to it, which is its proper role in the behavioral loop in the brain. In all likelihood, what happens in OCD is that evolutionary old circuits of the cortex, like those for washing and checking, break through the gate, probably because of a problem in the caudate nucleus. When there is no efficient gating, the person can become overwhelmed by these intrusive urges and act on them in inappropriate ways. These actions are called behavioral perseverations , a fancy name for compulsions. Specifically, compulsions are behavioral perseverations that a person knows to be inappropriate and genuinely does not want to be doing: The thought comes in the gate, the gate gets stuck open, and the thought keeps coming in over and over again. People then persevere in washing their hands or checking the stove, even though it makes no sense to do so. These actions may bring them momentary relief, but then—boom—because the gate is stuck open, the urge to wash or check breaks through again and again. To make matters worse, in all probability the more compulsions they do, the more rigidly the gate gets stuck.
    In the absence of a fully functioning striatum, the cortex must function in a way that requires conscious effort because unwanted thoughts and urges have a tendency to interfere. It is just this sort of conscious effort that is made in behavior therapy, when a person works to manage responses to intrusive urges.
    We have good reason to think that the person with OCD can’t get rid of those intrusive thoughts and urges because the circuit from the orbital cortex, the brain’s “early-warning detection system,” is firing inappropriately. The culprit may well be the lack of proper filtering by the caudate nucleus. Evolution may play a large role in the origins of classic OCD symptoms. Think of the kinds of automatic behaviors that were hardwired into the brain circuitry of our ancestors. In all likelihood, these behaviors had to do with avoiding contamination and checking to make sure that they were safe—that the cave was neither dirty nor dangerous, for example.

    STUCK IN GEAR
    In behavior therapy, we try