Both healthy adults and schizophrenic patients showed late parietal old/new effects that overlapped distinct auditory and visual P3 sources, which may reflect conscious experience of item retrieval (e.g., Friedman and Johnson, 2000; Rugg and Curran, 2007). This is entirely consistent with other neuroimaging evidence implicating old/new effects for the lateral posterior parietal cortex (e.g., Wagner et al., 2005). However, there were several topographical abnormalities associated with this parietal old/new effect in schizophrenia. First, whereas old/new source effects were fairly preserved over posterior midline sites, particularly in the visual modality, more lateral old/new sources were more severely reduced in patients. This was more obvious for the lateral-parietal auditory source pattern but nevertheless also present for visual stimuli. Second, these findinge were bolstered by the failure of patients to show the typical left-lateralized asymmetry of this parietal old/new effect, matching our prior data (Kayser et al., 1999). These abnormalities of parietal old/new source effects in this continuous recognition memory paradigm, as well as reduced overall P3 source amplitude and asymmetry, are not merely the result of slower or more variable responses in schizophrenia because the response-locked data indicated comparable, but somewhat weaker, reductions over left lateral parietal sites.
