Typical limitations of ERP studies in schizophrenia involve ongoing treatment with antipsychotic medication, small sample size, sample heterogeneity with respect to clinical features, and differences in task performance. Differential medication effects on auditory ERPs have been reported, for example, with clozapine treatment being associated with P3 enhancement,8 or risperidone treatment associated with reduced P3 latency.79 In a previous report,80 we found reduced N2 amplitudes in schizophrenia during these tonal and phonetic oddball tasks primarily for unmedicated patients. This is consistent with the current study, which included more unmedicated than medicated patients; however, it is not clear to what extent drug treatment had a moderating influence on the current findings. While the number of patients included in the present study (n = 23) was substantially smaller than the sample size of our previous study (n = 66),10 which likely caused a reduction in statistical power for detecting less robust effects, the current patient sample was reasonably large compared to sample sizes of many other studies. Also, the current study included a particularly well-matched sample of healthy controls. Although patients responded more
