While the basic paradigm closely matched standard auditory oddball tasks, it employed tonal and phonetic stimuli suitable to specifically probe left or right hemispheric functions.33,48,75 Most importantly, patients and controls showed the expected task-related asymmetries of N2 sinks and P3 sources favoring the right hemisphere for tones but the left hemisphere for syllables, thereby replicating our previous findings using tonal and phonetic oddball tasks in a large sample (n = 66) of schizophrenic patients.10 Moreover, in the present study, the left-lateralized parietal N2 sink for syllables was even more robust in patients than healthy controls, suggesting preserved categorization of phonemes (i.e., early encoding of linguistic information) in schizophrenia. The preserved task-related N2/P3 asymmetries in schizophrenia challenges the implicit notion that greater reductions of N2/P3 amplitude over left than right temporal sites are per se indicative of a left-lateralized dysfunction. This assumption would have predicted left-lateralized reductions of N2/P3 components regardless of task, or particularly for phonetic stimuli known to engage left-hemispheric processing.33,35,36 Instead, right-greater-than-left N2 and/or P3 amplitudes for tones,31,33,34 which are commonly used as stimuli in standard oddball tasks, represent the normal asymmetry pattern that is consistent with functional hemispheric differences for pitch processing in healthy adults.85,86
