Untitled

Modifying Brain Networks 407SchizophreniaA number of years ago, never-medicated schizophrenic patients were tested bothby imaging and by a cued detection task similar to the orienting part of the ANT.At rest, these patients in comparison with normals showed a focal decrease incerebral blood flow in the left globus pallidus, a part of the basal ganglia withclose ties to the anterior cingulate (Early, Posner, Reiman, & Raichle, 1989). Theyalso showed a deficit in orienting similar to what had been found for left-parietalpatients. When their visual attention was engaged, they had difficulty in shiftingattention to the right visual field, and they also showed deficits in conflict tasks,particularly when they had to rely on a language cue (Early et al., 1989). It wasconcluded that the overall pattern of their behavior was most consistent with adeficit in the anterior cingulate and basal ganglia, parts of a frontally based executiveattention system (see table 18-1 for the relation of these brain areas toexecutive attention).The deficit in orienting rightward has been replicated in schizophrenics whoare undergoing their first episode of the disorder, but it does not seem to be truelater when the disorder becomes chronic (Maruff, Currie, Hay, McArthur-Jackson,& Malone, 1995), nor does the pattern appear to be part of the genetic predispositionfor schizophrenia (Pardo, Knesevich, Vogler, Pardo, Towne, et al., 2000).Schizophrenic participants undergoing their first episode have often been shownto have left hemisphere deficits, and there have been many reports of anterior cingulateand basal ganglia deficits in patients with schizophrenia (Benes, 1999). Theanterior cingulate may be part of a much larger network of frontal and temporalstructures that operate abnormally in schizophrenia (Benes, 1999).A recent study using the ANT (Wang, Fan, Dong, Wang, Lee, et al., 2005) castssome light on these results. In this study, the schizophrenic patients were chronicand they were compared with a control group matched by age. The schizophrenicpatients had a much greater difficulty resolving conflict than did the normal controls.There was nevertheless a great deal of overlap between the patients andnormal subjects, indicating that ANT results are not sufficient for making a differentialdiagnosis. The data showed a much smaller orienting deficit in schizophrenicpatients. These findings suggest a strong executive deficit in chronicschizophrenia, as would be anticipated by Benes’s (1999) theory. It remains to bedetermined whether this deficit exists prior to the initial symptoms, or whether itdevelops with the disorder.Chromosome 22q11 Deletion SyndromeThis syndrome is a complex one that involves a number of abnormalities, includingfacial and heart structure, but also mental retardation due to deletion of anumber of genes. Children with the deletion are at a high risk for developing schizophrenia.Among the genes deleted in this syndrome is the COMT gene, which hasbeen associated with performance in a conflict task (Blasi et al., 2005; Diamond