Corollary discharge and efference copy mechanisms in schizophrenia and controls

<p>"Efference copy" and "corollary discharge” mechanisms may help to distinguish internal from external stimuli. Previous studies indicate that patients with schizophrenia show a lack of N1 evoked response potential component amplitude suppression to self-initiated auditory stimuli, suggesting a corollary discharge impairment. <br>In our study, we examined N1 and P2 component amplitude suppression in 27 patients with schizophrenia and 30 healthy controls using an auditory button-press paradigm. <br>In addition to symptom ratings we conducted neuropsychological assessments. Our findings replicated N1 amplitude suppression to self-generated tones in schizophrenia patients. <br>We found no correlation between N1, P2, and lateralized readiness potential, suggesting that the readiness potential may not directly represent corollary discharge mechanisms. <br>Cognition performance was reduced in schizophrenia patients and performance reduction correlated with negative symptoms.</p>
<p>Cognition was not associated with evoked potential data. Regarding the P2 component, P2 suppression to self-generated tones was observed in patients as well as in controls.  In conclusion, the N1 and the P2 component seem to be differentially involved in corollary discharge and efference copy mechanisms. Further investigation is needed to elucidate functional differences and sources of both components in this context.</p>
<p>It was approved by the Ethics Committee of the Medical Faculty of the University of Duisburg-Essen (No. 01-17-7753-B0).</p>
<b>Methods</b>
<ul>
<li>Number of participants: 57, including 30 healthy subjects (C = control) and 27 patients with schizophrenia (P = patient)</li>
<li>Number of sessions per participant: 3
<ul>
<li>Condition A = Generate Tone (subject generates a tone when clicking)</li>
<li>Condition B = Hear Tone (subject hears pre-recorded tones)</li>
<li>Condition C = Button Alone (subject does not generate tones when clicking)</li>
</ul>
</li>
<li>Recording: BrainVision Recorder (Version 1.1, Brain Products GmbH, Germany)</li>
<li>Data File: EDF+</li>
<li>Samplingrate: 1.000 Hz</li>
<li>Filter: 0.016 Hz to 250 Hz</li>
<li>Chanels: Fp1, FPz Fp2, F7, F3, Fz, F4, F8, FC1, FC2, FCz, FC5, FC6, T7, C3, Cz, C4, T8, CP5, CP1, CP2, CP6, P7, P3, Pz, P4, P8, O1, Oz, O2, A1, A2</li>
<li>Reference: FCz</li>
<li>Grounding: FPz</li>
<li>Markers/events: S1 = Marker for Condition A / “Generate Tone” (corresponding to clicking the button); S12 = Marker for Condition B / “Hear Tone” (corresponding to onset of auditory stimulus); S24 = Marker for Condition C / “Button Alone” (corresponding to clicking the button)</li>
</ul>
<p>Dataset for PANSS, WAIS and CCAS and prepared EEG analysis (N1/P2 and Readiness potential)</p>
<ul>
<li>Preparation for the EEG analysis: EEG re-referenced to connected earlobes, gross artifacts were removed, Eye movement artifacts were corrected, continuous EEG data were segmented into 3,000 ms epochs (-2,000 ms to +1,000 ms) time-locked to button press. EEG epochs were each artifact rejected for voltages greater than ±120 μV and then averaged
<ul>
<li>N1 and P2 analyses: data were baseline corrected from -100 ms to 0 ms, N1 and P2 peaks were identified at electrodes Fz, FCz, and Cz. To account for the motion-related effects of the “Generate Tone” condition in the statistical analyses, we removed the “Button Alone” condition from the “Generate Tone” condition.</li>
<li>Readiness potential Analysis: data was baseline-corrected from -2,000 ms to -1,800 ms, and then divided into ten 200 ms segments from -2,000 ms to 0 ms to derive the average amplitude values.</li>
</ul>
</li>
</ul>