Perceptual asymmetries in schizophrenia: subtype differences in left hemisphere dominance for dichotic fused words.

OBJECTIVE Dichotic listening techniques have been used to study hemispheric dominance for language in schizophrenia. The authors' goal was to compare subjects with paranoid and undifferentiated subtypes of schizophrenia. METHOD The Fused Rhymed Words Test was used to compare perceptual asymmetries in 16 patients with paranoid schizophrenia, 28 patients with undifferentiated schizophrenia, and 29 healthy comparison subjects. RESULTS Patients with paranoid schizophrenia had the largest left hemisphere advantage and patients with undifferentiated schizophrenia had the smallest. The asymmetry of healthy subjects was intermediate. Hemisphere advantage varied as a function of gender only in the patients with undifferentiated schizophrenia. CONCLUSIONS The findings support the hypotheses that undifferentiated schizophrenia is associated with underactivation of left hemisphere resources for verbal processing and that paranoid schizophrenia is characterized by preserved left hemisphere processing.