Left-greater-than-right asymmetry occurred in the depressive disorder patients, whereas right-greater-than-left asymmetry occurred in patients with anxiety disorders. These patient-dependent hemispheric asymmetries of dipole magnitude reflected foci locations in the scalp P300 topography at peak latency. Dipole activities in depressed patients revealed a left hemisphere advantage (in particular over the temporal site) when asked to perceive and respond to target tones, which was consistent with dichotic listening studies (Bruder et al. 1999; Liotti et al. 1991). Depressive disorder patients appeared to activate rather left than right-hemisphere regions during auditory tasks. The anxiety disorder group showed P300 evidence that a right hemisphere advantage existed in the frontal and temporal dipoles, particularly in the temporal dipoles. These results are consistent with previous PET studies suggesting decreased metabolism and cerebral blood flow in the left temporoparietal and inferior frontal cortex in panic disorder patients (Meyer et al. 2000; Nordahl et al. 1998; Lee et al. 2006; Sakai et al. 2006).
