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127. The Effect of Attention on the Auditory Evoked Potential in First Episode Psychosis
Reductions of the auditory N100 have been reported in first episode psychosis (FE). However, it is unclear if this abnormality results from sensory deficits or impaired enhancement of N100 by selective attention. N100 was recorded from 21 FE and 22 matched healthy controls (HC) on a single-tone and a two-tone oddball task. N100 was smaller in FE across tasks and attentional conditions (attend/unattended; p<.05). Attention enhanced N100 amplitude (p<.001), but this differed between groups: FE was impaired in such modulation (p=.018). The oddball task showed greater modulation than the single-tone task (p=.002), but this effect also differed between groups (p=.035). HC, but not FE, modulated N100 with attention more on the oddball than the single-tone task (p=.001), and group differences in N100 enhancement in the oddball task were quite large (Cohen’s d=.98). Tests on unattended conditions in both tasks showed no difference between groups. In terms of clinical and functional measurements, the FE N100 enhancement on the oddball task was correlated with higher premorbid IQ, better MATRICS Overall Composite scores, lower PANNS Negative factor scores, and lower SANS score. N100 was smaller in FE overall, but this likely reflects a failure in sensory modulation by attention. This suggests a long-range functional disconnection between cognitive control cortical areas and sensory cortex early in disease rather than abnormalities at the late sensory level. The modulation of N100 by attention may be a useful biomarker as it was associated with negative symptom severity and cognition.