Am J Psychiatry 1996; 153:714-717
Copyright © 1996 by American Psychiatric Association
Use of methods from chaos theory to quantify a fundamental dysfunction in the behavioral organization of schizophrenic patients
MP Paulus, MA Geyer and DL Braff
Department of Psychiatry 0804, University of California, San Diego, La Jolla 92093-0804, USA.
OBJECTIVE: This study aimed to quantify the complexity of behavioral
sequences of patients with schizophrenia and comparison subjects by using
methods from nonlinear dynamical systems theory. METHOD: A simple choice
task consisting of predicting 500 random right or left appearances of a
stimulus was used to obtain binary response sequences in 22 patients with
schizophrenia and 16 comparison subjects. Dynamical entropy was measured
and the fluctuation spectrum of local subsequence entropies calculated to
quantify the degree of interdependency between consecutive responses of
patients and comparison subjects. RESULTS: The response sequences generated
by the schizophrenic patients exhibited a higher degree of interdependency
than those of comparison subjects. Moreover, schizophrenic patients
exhibited significantly less consistency in their response selection and
ordering, characterized by a greater contribution of both highly
perseverative and highly unpredictable subsequences of responses within a
test session. CONCLUSIONS: The result of the biological abnormality
underlying schizophrenia may not be a simple increase or decrease of
neuropsychological or neurobiological functions. Instead, the observed
abnormalities in behavioral patterns reflect a quantifiable dysregulation
and disorganization of these functions.
