Analysis of classification methods suitable for band limited spatially filtered EEG signal applicable to non-invasive BCI

Electroencephalographic (EEG) signals are the preferred input for non-invasive Brain-Computer Interface (BCI). Efficient signal processing strategies, including feature extraction and classification, are required to distinguish the underlying task of BCI. This work proposes the optimized common spatial pattern(CSP) filtering technique as the feature extraction method for collecting the spatially spread variation of the signal. The bandpass filter (BPF) designed for this work assures the availability of event-related synchronized (ERS) and event-related desynchronized (ERD) signal as input to the spatial filter. This work takes consideration of the area-specific electrodes for feature formation. This work further proposes a comparative analysis of classifier algorithms for classification accuracy(CA), sensitivity and specificity and the considered algorithms are Support Vector Machine(SVM), Linear Discriminant Analysis(LDA), and K-Nearest Neighbor(KNN). Performance parameters considered are CA, sensitivity, and selectivity, which can judge the method not only for high CA but also inclining towards the particular class. Thus it will direct in the selection of appropriate classifier as well as tuning the classifier to get the balanced results. In this work, CA, the prior performance parameter is obtained to be 88.2% sensitivity of 94.2% and selectivity 82.2% for the cosine KNN classifier. SVM with linear kernel function also gives the comparable results, thus concluding that the robust classifiers perform well for all parameters in case of CSP for feature extraction.

Abstract 473: Differential Regulation of Sk Channels by CamKII and Pyk2 Under Adrenergic Stimulation

Introduction: Small conductance calcium (Ca)-activated K (SK) channels present in the plasmalemma of ventricular cardiomyocytes (VCMs) are dormant in health and become functional in cardiac disease. We recently showed that SK channels contribute to VCM repolarization in a rat model of hypertrophy induced by thoracic aortic banding (TAB), despite reduced expression levels, suggestive of increased activity of the channels. However, the mechanisms responsible for disease-associated functional upregulation of the channels are yet to be defined. Hypothesis: Functional recruitment of SK channels in cardiac hypertrophy is caused by enhancement of adrenergic signaling cascades. Methods: The effects of α1 adrenergic stimulation by phenylephrine (10 μM) + propranolol (100 μM) were studied in patch-clamped rat VCMs overexpressing rat SK2 after 48 hrs in culture. Calcium transients were recorded simultaneously using confocal microscopy and were used as a ramp [Ca] to assess possible changes in Ca sensitivity of the channel. Phosphorylation of SKs by Ser/Thr and tyrosine kinases, phosphorylation of Calmodulin at Thr-79, expression levels and phosphorylation of CaMKII and tyrosine kinase Pyk2 were assessed in cultured rat VCMs and freshly isolated VCMs from TABs and Shams using Western blot analysis. Results: WB analysis showed increased Ser/Thr and Tyr phosphorylation of SK2 in TABs. Alpha1 stimulation of rat VCMs overexpressing rat SK2 mimicked this pattern, increasing I SK at high voltages in parallel with the increase in Ca transient amplitude and reduction in Ca sensitivity of the channels. Overexpression of Pyk2 inhibitor CRNK did not restore I SK despite reduction in Ca transient amplitude because of attenuating α1-agonist mediated decrease in Ca sensitivity of SKs. Application of CaMKII inhibitor KN93 fully reversed α1-mediated I SK increase at high voltages without affecting Ca sensitivity of the channel. Conclusion: Upregulation of SKs in hypertrophic hearts is likely caused by CaMKII-dependent phosphorylation which reduces voltage-dependent block of the channels. Pyk2 inhibition may present therapeutic potential by attenuating negative effects on SK Ca sensitivity thereby increasing repolarization reserve diminished in cardiac disease.

Sex-based differences in myocardial contractile reserve

Recent studies have identified sex differences in heart function that may affect the risk of developing heart failure. We hypothesized that there are fundamental differences in calcium (Ca) regulation in cardiac myocytes of males and premenopausal females. Isometric force transients ( n = 45) were measured at various stimulation frequencies to define the force frequency responses (FFR) (0.5, 1.0, 1.5, and 2.0 Hz) during either changes in bath Ca ([Ca]o) (1.0, 1.75, 3.5, and 7.0 mM) or length-tension (20, 40, 60, 80, and 100% Lmax) in right ventricle trabeculae from normal male (MT) and premenopausal female (FT) cats. Force-Ca measurements were also obtained in chemically skinned trabeculae. Under basal conditions (0.5 Hz, 1.75 mM Ca, 80% Lmax) both MT and FT achieved similar developed forces (DF) (MT 11 ± 1, FT = 10 ± 1 mN/mm2). At low rates and lengths, there is no sex difference. At higher preloads and rates, there is a separation in DF in MT and FT. At basal [Ca]o both MT and FT exhibited positive FFR (2.0 Hz, 1.75 mM Ca: MT 38 ± 3, FT 21 ± 4 mN/mm2); however, at higher [Ca]o, MT achieved greater DF (2.0 Hz, 7.0 mM Ca: MT 40 ± 3 and FT = 24 ± 4 mN/mm2). We detected no sex difference in myofilament Ca sensitivity at a sarcomere length of 2.1 μm. However, rapid cooling contractures indicated greater sarcoplasmic reticulum (SR) Ca load in MT at higher frequencies. Despite virtually identical contractile performance under basal conditions, significant sex differences emerge under conditions of increased physiological stress. Given the lack of sex differences in myofilament Ca sensitivity, these studies suggest fundamental sex differences in cellular Ca regulation to achieve contractile reserve, with myocardium from males exhibiting higher SR Ca load.