Linear and nonlinear analysis of intrinsic mode function after facial stimuli presentation in children with autism spectrum disorder.

In this work, a method for classifying Autism Spectrum Disorders (ASD) from typically developing (TD) children is presented using the linear and nonlinear Event-Related Potential (ERP) analysis of the Electro-encephalogram (EEG) signals. The signals were acquired during the presentation of three types of face expression stimuli -happy, fearful and neutral faces. EEGs are first decomposed using the Multivariate Empirical Mode Decomposition (MEMD) method to extract its Intrinsic Mode Functions (IMFs), which provide information about the underlying activities of ERP components. The nonlinear sample entropy (SampEn) features, as well as the standard linear measurements utilizing maximum (Max.), minimum (Min), and standard deviation (Std.), are then extracted from each set of IMFs. These features are then evaluated by the statistical analysis tests and used to construct the input vectors for the Discriminant analysis (DA), Support vector machine (SVM), and k-Nearest Neighbors (kNN) classifiers. Experimental results show that the proposed features can differentiate the ASD and TD children using the happy stimulus dataset with high classification performance for all classifiers that reached 100% accuracy. This result suggests a general deficit in recognizing the positive expression in ASD children. Additionally, we found that the SampEn measurements computed from the alpha and theta bands and the linear features extracted from the delta band can be considered biomarkers for disturbances in Emotional Facial Expression (EFE) processing in ASD children.