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2005 baxter et al 2001 1990 the serotonin and brain

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Unformatted text preview: ese regions are part of a brain circuit that usually converts sensory information into thoughts and actions (Stein & Fineberg, 2007). The circuit begins in the orbitofrontal cortex, where sexual, violent, and other primitive impulses normally arise. These impulses next move on to the caudate nuclei, which act as filters that send only the most powerful impulses on to the thalamus, the next stop on the circuit (see Figure 4-7). If impulses reach the thalamus, the person is driven to think further about them and perhaps to act. Many theorists now believe that either the orbitofrontal cortex or the caudate nuclei of some people are too active, leading to a constant eruption of troublesome thoughts and actions (Lambert & Kinsley, 2005). Additional parts of this brain circuit have also been identified in recent years, including the cingulate cortex and, once again, the amygdala (Stein & Fineberg, 2007). It may turn out that these regions also play key roles in obsessive-compulsive disorder. In support of this brain circuit explanation, medical scientists have observed for years that obsessive-compulsive symptoms do sometimes arise or subside after the orbitofrontal cortex, caudate nuclei, or other regions in the circuit are damaged by accident or illness (Coetzer, 2004). Similarly, brain scan studies have shown that the caudate nuclei and the orbitofrontal cortex of research participants with obsessive-compulsive disorder are more active than those of control participants (Chamberlain et al., 2005; Baxter et al., 2001, 1990). The serotonin and brain circuit explanations may themselves be linked. It turns out that serotonin—along with the neurotransmitters glutamate, GABA, and dopamine— plays a key role in the operation of the orbitofrontal cortex, caudate nuclei, and other parts of the brain circuit; certainly Caudate nucleus abnormal activity by one or more of these neurotransmitters could be contributing to the improper functioning of the circuit. Ever since researchers first discovered that certain antiThalamus depressant drugs help to reduce obsessions and compulsions, these drugs have been used to treat obsessive-compulsive disorder ( Julien, 2008). We now know that the drugs not only increase brain serotonin activity but also help produce more Amygdala normal activity in the orbitofrontal cortex and caudate nuclei (Stein & Fineberg, 2007; Baxter et al., 2000, 1992). Studies have found that clomipramine (Anafranil), fluoxetine (Prozac), fluvoxamine (Luvox), and similar antidepressant drugs bring improvement to between 50 and 80 percent of those with obsessive-compulsive disorder (Bareggi et al., 2004). The obsessions and compulsions do not usually disappear totally, but on average they are cut almost in half within eight weeks of treatment (DeVeaugh-Geiss et al., 1992). People who are treated with such drugs alone, however, tend to relapse if their medication is stopped. Thus, more and more individuals with obsessive-compulsive disorde...
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