Severity of negative symptoms in schizophrenia correlated to hyperactivity of the left globus pallidus and the right claustrum. A PET study.

Schizophrenia has been characterized as a complex disease, in which various cerebral regions may be affected. The purpose of this study was to compare the cerebral regions that are involved in mild and severe negative symptoms, and to determine whether the degree of severity can be related to specific dysfunctional areas of the brain. The PANS Scale was used to form two groups of patients with prevalence of negative symptoms: Mildly Affected (MA), and Severely Affected (SA). Brain PETs were obtained in resting conditions, and SPM (Statistical Parametric Mapping) was used to perform statistical comparisons. The MA-group showed increased activity in: posterior cingulate gyrus, middle frontal gyrus, precentral gyrus, middle occipital gyrus, cuneus and post-central gyrus; decreased activity in inferior frontal gyrus, orbitofrontal and fusiform gyrus. The SA-group showed increased activity in: globus pallidus, insular cortex, cuneus, claustrum, post-central gyrus and pre-central gyrus; decreased activity in fusiform gyrus and superior temporal gyri. These results permit correlation of negative symptomatology with abnormalities in the cortico-striato-pallido-thalamic neural circuit. Severity of negative symptoms is clearly correlated to abnormal left external pallidal activation, evidencing the relevance of this nucleus for cognitive, planning and social capabilities. Specific therapeutic strategies might be derived from pallidal neurotransmitter systems studies. Key words: schizophrenia, negative symptoms, severity, PET, globus pallidus, claustrum.