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April 1991

Is There P300 Asymmetry in Schizophrenia?-Reply

Author Affiliations

Department of Psychiatry and Behavioral Sciences Stanford University Medical School Veterans Affairs Medical Center Psychiatry Service, 116A3 3801 Miranda Ave Palo Alto, CA 94305

Arch Gen Psychiatry. 1991;48(4):381-383. doi:10.1001/archpsyc.1991.01810280097017

In Reply.—  McCarley et al wrote to inform us of new data from their laboratory regarding P300 amplitude asymmetries in schizophrenia.1 They report P300 asymmetry in schizophrenic patients "using only the waveform associated with the target stimulus." Previously, they derived P300 by a complex subtraction procedure involving P300s elicited under various conditions. Analysis of P300 to target stimuli alone is the more traditional approach and the one we use routinely. However, with this technique, we failed to obtain P300 asymmetry in schizophrenic patients.2 It should be noted that the McCarley group also failed earlier to obtain P300 asymmetries in schizophrenic patients using the more traditional P300. In that report,3 not cited in their letter, they report, "Thus, no statistically significant P300 ia topographic group differences were present." (P300ia indicates attended target P3003(p124)). They concluded that the primary source of the P300 left/right temporal region topographic difference observed

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