Abnormal Psychology

Anxiety Disorders 303

in particular (Insel, 1992; Pigott, Myers, & Williams, 1996; Saxena & Rauch,

2000). In fact, as predicted by the theory, both the frontal cortex (especially the

orbital frontal cortex—the lower parts of the cortex, behind the eyes) and the basal

ganglia function abnormally in OCD patients (Baxter, 1992; Berthier et al., 2001;

Saxena et al., 1998). This abnormal functioning could well prevent the frontal

lobe from cutting off the loop of repetitive neural activity, as it appears to do in

normal people.

Researchers have also suggested that OCD is associated with larger amounts of

gray matter in the frontal lobes and smaller amounts in the posterior portions of the

brain (Kim et al., 2001). Such structural abnormalities are consistent with the un-

usually large amount of activity in patients’ frontal regions when they see a stimulus

that provokes the OCD-related thoughts and behaviors (Adler et al., 2000). Fur-

thermore, these patients have impaired visual-spatial abilities, which rely on similar

areas of the brain (Micallef & Blin, 2001).

However, not all studies have found such brain abnormalities (Baxter, Schwarz, &

Guze, 1991), which may suggest that there is more than one way OCD can arise

(Hollander, Liebowitz, & Rosen, 1991). In fact, researchers have found that many

(but not all) patients with OCD had an abnormal birth, epilepsy, head trauma, or

infection of the brain or the membranes that cover it. For example, as we saw in

Chapter 5, when children rapidly develop symptoms of OCD, the cause may be a

particular type of streptococcal infection that leads to a disorder in the immune

system, which is called pediatric autoimmune neuropsychiatric disorder associ-

ated with streptococcal infection. This disorder affects the basal ganglia (Swedo

et al., 1998). Symptoms of OCD disappear when the children take the appropriate

antibiotics.

Frontal lobe

Basal ganglia

Thalamus

Frontal lobe

Basal ganglia

Thalamus

Figure 7.14

7.14 • The Neural Loop That May Underlie Obsessive Thoughts The basal

ganglia, the thalamus, and the frontal lobes are part of a neural loop of repeating brain activity

associated with OCD.