USE OF METHODS FROM CHAOS THEORY TO QUANTIFY A FUNDAMENTAL DYSFUNCTION IN THE BEHAVIORAL ORGANIZATION OF SCHIZOPHRENIC-PATIENTS

Objective: This study aimed to quantify the complexity of behavioral s equences of patients with schizophrenia and comparison subjects by usi ng methods from nonlinear dynamical systems theory. Method: A simple c hoice task consisting of predicting 500 random right or left appearanc es of a stimulus was used to obtain binary response sequences in 22 pa tients with schizophrenia and 16 comparison subjects. Dynamical entrop y was measured and the fluctuation spectrum of local subsequence entro pies calculated to quantify the degree of interdependency between cons ecutive responses of patients and comparison subjects. Results: The re sponse sequences generated by the schizophrenic patients exhibited a h igher degree of interdependency than those of comparison subjects. Mor eover, schizophrenic patients exhibited significantly less consistency in their response selection and ordering, characterized by a greater contribution of both highly perseverative and highly unpredictable sub sequences of responses within a test session. Conclusions: The result of the biological abnormality underlying schizophrenia may not be a si mple increase or decrease of neuropsychological or neurobiological fun ctions. Instead, the observed abnormalities in behavioral patterns ref lect a quantifiable dysregulation and disorganization of these functio ns.