ERP research in schizophrenia relying on simple oddball tasks has generally not used paradigms specifically designed to probe left or right hemispheric functions (but see Kayser et al., 2001; Bruder et al., 2001), or to target linguistic and mnemonic processes. Semantic context and recognition memory have been widely studied in healthy populations with a variety of experimental paradigms (e.g., N400), which are increasingly applied to psychiatric populations (e.g., Kumar and Debruille, 2004). One of the most robust findings in ERP memory research is the old/new effect, a more positive-going potential for previously-studied and correctly-recognized old than new items that begins at about 300 ms post stimulus onset, lasts several hundred milliseconds, and has a left parietal maximum (e.g., reviewed by Johnson, 1995; Allan et al., 1998; Friedman, 2000; Mecklinger, 2000). Whereas this late ERP old/new effect is considered an electrophysiological correlate of explicit memory-retrieval processes (conscious recollection), an earlier mid-frontal old/new effect that peaks around 400 ms is regarded as an index of implicit knowledge that a stimulus event has been previously experienced (item familiarity), suggesting different neural generators of
