P383 Multiscale lempel-ZIV complexity in schizophrenia at rest and while performing a naming task

Schizophrenic patients show cognitive deficits which are evident in EEG measures. Recent studies have suggested that non-linear EEG indexes might more adequately reflect the complex, irregular, nonstationary behavior of neural processes in schizophrenia than more traditional ERP measures (Fernandez et al., 2011). So far, non-linear analyses have mainly been performed to EEGs from patients at rest, whereas differences in complexity might be more evident during task performance. In addition, most studies have explored complexity at a single time scale. Objective We aimed to investigate changes in nonlinear multiscale brain dynamics in schizophrenic patients during cognitive processing. Method 18 patients and 17 matched healthy controls were asked to name pictures. EEG data were collected at rest and while they were performing the task. EEGs were analyzed with the classical and the multiscale Lempel-Ziv Complexity. Electrodes were grouped in seven regions of interest (ROI). Results Controls had fewer naming errors than patients. More importantly, we found greater complexity values for patients than for controls in right frontal regions, at rest. The interaction between Group, Task and ROI indicated that differences between patients and controls were more evident when performing the task, with increments in brain complexity in left temporal parietal regions, only in the control group. Conclusions We found different modulations of brain complexity during a simple cognitive task between patients and controls. These data can be interpreted as a failure of patients to adapt their brain functioning to the task, which reflect in poorer behavioral performance.