Decoding and classification of objects through task-oriented electroencephalographic (EEG) signals are the most crucial goals of recent researches conducted mainly for brain-computer interface applications. In this study we aimed to classify single-trial 12 categories of recorded EEG signals. Ten subjects participated in this study. The task was to select target images among 12 basic object categories including animals, flowers, fruits, transportation devices, body organs, clothing, food, stationery, buildings, electronic devices, dolls and jewelry. In order to decode object categories, we have considered several units namely artifact removing, feature extraction, feature selection, and classification. Data were divided into training, validation, and test sets following the artifact removal process. Features were extracted using three different wavelets namely Daubechies4, Haar, and Symlet2. Features were selected among training data and were reduced afterward via scalar feature selection using three criteria including T test, entropy, and Bhattacharyya distance. Selected features were classified by the one-against-one support vector machine (SVM) multi-class classifier. The parameters of SVM were optimized based on training and validation sets. The classification performance (measured by means of accuracy) was obtained approximately 80 % for animal and stationery categories. Moreover, Symlet2 and T test were selected as better wavelet and selection criteria, respectively.
In this article a quantitative analysis was devised assessing driver’s cognition responses by exploring the neurobiological information underlying electroencephalographic (EEG) brain signals in a left and right turning experiment on simulator environment. Driving brain signals have been collected by a 19-channel electroencephalogram recording system. The driving pathway has been selected with no obstacles, a set of indicators are used to inform the subjects when they had to turn left or right by means of keyboard left and right arrows. Subsequently in order to remove artifacts, preprocessing is performed on data to achieve high accuracy. Features of signals are extracted by using Fast Fourier Transform (FFT). Absolute power of FFT is used as a basic feature. Scalar Feature selection method is applied to reduce feature dimension. Thereafter dimension-reduced features are fed to Hopfield Neural Network (HNN) recognizing different brain potentials stimulated by turning to left and right. The performances of HNN are evaluated by considering five conditions; before feature extraction, after feature extraction, before reduction of features, after analyzing reduced features and finally subject-wise Hopfield performances respectively. An increase occurred in each level and continued until it has reached its highest 97.6% of accuracy on last condition.
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