Applying approximate entropy and central tendency measure to analyze time series generated by schizophrenic patients

The purpose of this study is the analysis of times series generated by 20 schizophrenic patients and 20 age-matched control subjects. We used two methods for quantifying the regularity and variability in the time series. These methods were the Approximate Entropy (ApEn), and a graphical representation by means of the second-order difference plots to estimate the Central Tendency Measure (CTM). Results showed that the degree of irregularity and variability of the time series generated by the schizophrenic patients were lower than time series generated by the control group. Thus, schizophrenic patients tended to generate more regular and rhythmic series than control subjects. There was a significant difference with the ANOVA procedure (p<0.001) between time series generated by both groups. These results were in agreement with findings that schizophrenic patients were characterized by less complex neurobehavioral measurements than normal subjects.