SA73. Deficits in Attentional Modulation of Auditory Stimuli in First-Episode Schizophrenia

Abstract

Abstract Background: Auditory deficits have been reported in schizophrenia patients, specifically when using passive tasks to look at mismatch negativity and active tasks to look at P3 suppression in event-related potentials. Attentional deficits have also been reported, so we created a task to determine whether these 2 symptoms were related. Methods: Thirteen first-episode schizophrenia participants and 11 matched healthy control participants heard sounds while watching a silent nature video. The task focuses on N1 auditory event-related potentials and how their size changes under different attention loads. Participants heard standard tones (1k Hz, 50 ms duration, 5 ms ramp) spaced 1050 ms to 1550 ms apart. In one condition, participants were told to ignore tones while in the other condition participants counted tones in groups of 7. Electroencephalography data were recorded from the subjects during the task, and the data were filtered between 0.5 Hz and 20 Hz. It was then processed using ICA to remove eye blinks, eye movements, and heartbeat components. The N1 size was measured using the area of the curve that occurred from 100 ms to 110 ms. Results: Both healthy participants and first episode participants produced an N1 to the tones. There was no main effect of attention or group (Ps > .1). There was a significant interaction effect between group membership and effect of attention (P = .029). The healthy subjects showed larger N1 in the attend condition compared with the ignore condition (P = .074). However, the first-episode subjects showed no significance between attend and ignore conditions (P > .1). In the attend condition, healthy controls N1 was significantly larger than first-episode patients’ (P = .03), but there was no group difference in the ignore condition (P > .1). Conclusion: Our results showed that healthy controls enhance their N1 response with attention, and this effect is not seen in the schizophrenia group. These findings suggest that the auditory deficits experienced by schizophrenia patients may not be the result of abnormalities in the auditory cortex, but abnormalities in the top-down modulation of attention. Clinically, this could result in a potential biomarker for the diagnosis of schizophrenia in high-risk individuals. Further examination of this connection could also lead to a better understanding of auditory neurophysiology in schizophrenia.