Lower perturbational complexity index after transcranial magnetic stimulation in schizophrenia patients

Abstract

Background: Informational integration and differentiation of the cortex can be tested by methods such as the perturbational complexity index (PCI) combined with TMS-induced activity perturbation. The PCI is obtained by stimulating the cortex with TMS and measuring the resulting spatiotemporal cortical responses with high-density EEG. Methods: We have compared PCI between 26 patients with schizophrenia (15 males), 15 of them First Episode (FE) (7 males), and 22 healthy controls (12 males). Results: Values of PCI were significantly lower in patients with schizophrenia, as well as in FE considered alone. There was no significant relation between anomalous self-experiences or symptoms and PCI values in the pa- tients: PCI values were unrelated to treatment doses or illness duration. Conclusions: Our data suggest that spatiotemporal cortical responses to TMS pulses are reduced in patients regarding variability or spatial extension, which could imply a lower capacity for sustaining informational complexity.