Zouridakis, George2013-10-142013-10-14August 2012012-08http://hdl.handle.net/10657/457Objective: In this Master Thesis, we employed auditory evoked responses to identify features from the time domain signals, Granger Causality matrixes and graph theory that provide maximum separation among schizophrenic patients, cocaine addicts and normal controls. Methods: We analyzed data from 12 schizophrenia, 12 cocaine addicts and 12 normal control subjects. Responses were obtained in a paired-stimulus paradigm, in which auditory stimulus S1 is followed by an identical S2. Amplitude and latency of the N100 component were measured from the averaged evoked potential, Granger Causality matrixes were computed and a graph was constructed from there. Amplitude, latency, Granger Causality values and a group of characteristics form the graph were used as features to cluster responses in three groups. Several methods were used for clustering, while their performance was quantified in a 10-fold cross validation approach. Results: We found that the most important features come from Granger Causality matrix values, amplitude and latency coming from the average evoked responses appear as insignificant features for the clustering. Influence of electrode C3 to Pz appear as the most significant feature, separating schizophrenic patients from normal controls and cocaine addicts with a 100% accuracy. In order to separate cocaine addicts from normal controls at least 31 features coming from Granger Causality matrixes were needed. Conclusions: Our results demonstrate that Granger Causality values can accurately separate schizophrenia patients, cocaine addicts and normal controls and suggest that the Pz-C3 region plays a significant role in information processing in human brain. i Significance: The proposed technique may have a significant impact as a clinical tool in the quest for identifying physiological markers of schizophrenia. iiapplication/pdfengThe author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s).AEPSchizophreniaCocaineGranger causalityClusteringSchizophrenia2013-10-14Thesisborn digital