reported a reduction of auditory N1 amplitude in CHR patients, several cross-sectional studies observed reductions in MMN, showing that CHR individuals had reduced MMN amplitude to deviant tones differing from standard 1000-Hz tones in stimulus duration (Atkinson et al., 2012; Hsieh et al., 2012; Jahshan et al., 2012; Murphy et al., 2013; Shin et al., 2009). Studies that directly compared individuals with or without subsequent transition to psychosis found MMN reductions to be more severe or only present in those patients who later developed psychosis (Bodatsch et al., 2011; Higuchi et al., 2013; Shaikh et al., 2012). Brockhaus-Dumke et al. (2005) found only a non-significant MMN reduction in CHR patients, which was intermediate between controls and schizophrenia patients. As in schizophrenia, MMN deficits in CHR patients appear to be more robust for deviations in tone duration rather than pitch, and may also only be present in low but not high functioning patients (Hay et al., 2013).
