negative ERP deflections in the 200–400 ms time range after stimulus onset, with some processes, such as attention, tied in with modality-specific N2 topographies and generators. It is also plausible to conjecture that these vertex N2 sinks belong in the class of N400-like potentials indexing decision making during linguistic processes (cf. Silva-Pereyra et al., 2003). In any case, the marked N2 sink reductions across modality for words are similar to those seen for schizophrenic patients in visual or auditory discrimination tasks (e.g., O’Donnell et al., 1993; Egan et al., 1994; Strandburg et al., 1994; Bruder et al., 1998, 1999; Kayser et al., 2001; Umbricht et al., 2006). They are also consistent with our ERP findings involving phonetic discrimination of consonant-vowel syllables, in which smaller N2 amplitude in schizophrenic patients was associated with poorer verbal memory performance (Bruder et al., 2001). In context of these converging findings, we interpret the present N2 sink results as evidence of impaired stimulus categorization in schizophrenia at a cognitive stage beyond visual or auditory word form processing, which adversely affects word recognition memory.
