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131.
Ibrahim Onaran N. Firat Ince A. Enis Cetin 《Biomedical signal processing and control》2013,8(3):282-288
Common spatial pattern (CSP) method is widely used in brain machine interface (BMI) applications to extract features from the multichannel neural activity through a set of spatial projections. These spatial projections minimize the Rayleigh quotient (RQ) as the objective function, which is the variance ratio of the classes. The CSP method easily overfits the data when the number of training trials is not sufficiently large and it is sensitive to daily variation of multichannel electrode placement, which limits its applicability for everyday use in BMI systems. To overcome these problems, the amount of channels that is used in projections, should be limited to some adequate number. We introduce a spatially sparse projection (SSP) method that exploits the unconstrained minimization of a new objective function with approximated ?1 penalty. Unlike the RQ, this new objective function depends on the magnitude of the sparse filter. The SSP method is employed to classify the multiclass ECoG and two class EEG data sets. We compared our results with a recently introduced sparse CSP solution based on ?0 norm. Our method outperforms the standard CSP method and provides comparable results to ?0 norm based solution and it is associated with less computational complexity. We also conducted several simulation studies on the effect of noisy channel and intersession variability on the performance of the CSP and sparse filters. 相似文献
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Rats were exposed for 10 minutes to one of several enclosures graded in novelty. In one experiment they were then simply sacrificed and plasma corticosterone determinations made in order to obtain an index of the relative stressfulness of these enclosures. In a second experiment the animals received haloperidol and were tested for catalepsy, 2 hours or two weeks following the novel experience. The most novel experience, exposure to a black box, resulted in the highest corticosterone levels and was the only one of our pre-treatments to induce significant enhancement of catalepsy as well as alteration of nucleus accumbens dopamine levels, 2 weeks--but not 2 hours--later. These findings indicate that brief exposure of adult animals to a psychological stressor can induce a long-term alteration in both behavioral and neurochemical responses to a drug and that this effect requires a minimum level of stress to get started and once triggered gets stronger with the passage of time. 相似文献
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Schizogonous tissue stages of Cytauxzoon felis (Apicomplexa: Theileridae) were not observed by microscopic evaluation of impression smears of liver, spleen, lung and lymph nodes in 10 bobcats (Lynx rufus) from Oklahoma with naturally occurring piroplasm infections. Schizogonous stages were observed in similar tissues from experimentally-infected bobcats at 11 days postexposure to infected Dermacentor variabilis, but not at 30 days following tick feeding. The schizogonous cycle of this parasite appears to be short, although the bobcat appears to be a long-term carrier. 相似文献
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