Although the small sample size is a limitation of the present study, with only three CHR patients who later developed psychosis, this proportion is on par with previously reported transition rates (e.g., Gee & Cannon, 2011; Simon et al., 2011). However, the observation that the CSD waveforms to novel stimuli for these three converters prominently featured the characteristic novelty vertex source (Tenke et al., 2010) but surprisingly lacked a preceding novelty MMN, is intriguing given reports of impaired duration MMN in CHR patients (Atkinson et al., 2012; Bodatsch et al., 2011; Brockhaus-Dumke et al., 2005; Higuchi et al., 2013; Hsieh et al., 2012; Jahshan et al., 2012; Murphy et al., 2013; Shaikh et al., 2012; Shin et al., 2009). While we cannot stress enough the preliminary nature of this curious observation, it nevertheless underscores the potential value of MMN as a predictor of transition to psychosis. Taken together, the present ERP and ERSP findings reveal electrophysiological abnormalities in CHR patients during an auditory oddball paradigm that warrant further research with larger samples employing longitudinal or cross-sectional designs.
