Wiemer, P.,Jemel, B., Kreul, K., Röpcke, B., Oknina, L., Oades, R. (2002).
Frontal Mismatch Sources of Auditory Change Detection: Altered Asymmetry in First-Episode Adolescent Schizophrenia and Outpatients 15 Years Later.
European Archives of Psychiatry and Clinical Neuroscience, 252, supplement 1, p. 49.

Introduction: By comparison with common standard tones, rare deviant sounds elicit an event-related potential known as the Mismatch Negativity (MMN). MMN amplitude in response to auditory change is reduced in nonparanoid more than in paranoid forms of schizophrenia (Oades et al. 1997, Biol. Psychiat., 41, 1196-1210). BESA dipole source models in normal subjects fitted to Talairach space are described (see also Jemel et al., 2001, NeuroImage, 13, 323; 2002, Brain Topogr., 15, 13-27).

Methods:The present preliminary source current density analysis compares young patients with early onset schizophrenia (<18y) with outpatients 15 years after their first admission as adolescents. MMN was recorded from 32 leads in a three tone oddball paradigm using pitch- and duration deviants.

Results:
1) The two deviant sounds showed similar dipole sources.
2) Temporal lobe sources appeared more lateral and deeper in the right than in the left hemisphere.
3) In both sets of patients more diffuse and anterior inferior frontal sources on the right contrasted with more posterior anterior cingulate sources on the left.
4) Current density analysis in the patients showed a smaller MMN that had shifted to the left in both patient groups, implying a weaker contribution from the right hemisphere.

Conclusions:
- - The right frontal sources in normal healthy controls are close to images of preconscious visual change detection (Beck et al Nature Neurosci., 4, 645-650).
- - The results are consistent with electrophysiological and anatomical changes reported previously for the right cerebral hemisphere in early-onset patients with schizophrenia (Matsumoto et al. 2001, Am. J. Psychiat., 158, 1299-1304.