This paper aims to realize the decoding of single trial motor imagery electroencephalogram (EEG) signal by extracting and classifying the optimized features of EEG signal. In the classification and recognition of multi-channel EEG signals, there is often a lack of effective feature selection strategies in the selection of the data of each channel and the dimension of spatial filters. In view of this problem, a method combining sparse idea and greedy search (GS) was proposed to improve the feature extraction of common spatial pattern (CSP). The improved common spatial pattern could effectively overcome the problem of repeated selection of feature patterns in the feature vector space extracted by the traditional method, and make the extracted features have more obvious characteristic differences. Then the extracted features were classified by Fisher linear discriminant analysis (FLDA). The experimental results showed that the classification accuracy obtained by proposed method was 19% higher on average than that of traditional common spatial pattern. And high classification accuracy could be obtained by selecting feature set with small size. The research results obtained in the feature extraction of EEG signals lay the foundation for the realization of motor imagery EEG decoding.
【Abstract】 Objective To reconstruct three different kinds of tympanic membrane in vitro by tissue engineeringtechnique, and to examine their histological structures and mechanical properties. Methods The skin and dura of pig(weight 30 kg) were processed with high satuated sal ine and enzymes to make extracellular matrix. Meanwhile, fibroblasts(1×106 /mL,0.2 mL) were seeded on the surface of these two scaffolds and collagen. The composite tissues were cultured in vitro for 1 week and examined in histological structure and mechanical properties. Results Fibroblasts cultured were spindle–shaped and could grow and attach to these scaffolds with a arrangement of sarciniform and parallel. The reconstructed tissue of ECM and collagen appeared to integrate well and had better bio-compatibil ity. The mean thickness of the collagen, the skin and the dura (all covered with fibroblasts) were 9.4, 10.0 and 10.4 μm respectively. The tension of the collagen was (1.417±0.030) N/mm2, of the acellular dermal matrix was (24.500±2.040) N/mm2(being close to the tension of normal tympanic membrane, 26.700 N/ mm2),of the acellular dura was (53.300±2.600) N/mm2. Conclusion The results suggest that the tension and the thinkness of acellular dermal matrix is similar to the normal tympanic membrane of guinea pig, it is an ideal material for tympanoplasty.