Просмотр исходного текста страницы At Least Two Remarkable Things Concerning C59

The singular value decomposition of STS can be written STS=U��V? (23) where �� is a diagonal matrix of the singular values and U and V are unitary square matrices. The pseudo-inverse of STS is then given by (STS)+=V��+U?. (24) A regularization strategy is applied to the singular value matrix, ��, during inversion to form the regularized pseudo-inverse. It requires selection of a single hyper-parameter �� which specifies the tolerance of the regularization and is optimized using a cross-validation procedure. The number of stimulus dimensions to preserve, m, is computed by m=arg?max��1+��2+��+��m��1+��2+��+��MN[http://www.selleckchem.com/products/wnt-c59-c59.html Selleckchem C59] generation mechanism. For example, an inhomogeneous Poisson process can be used to generate spike trains in a probabilistic manner from the rate. Here, a two stage model is used in which a receptive field model is adapted to produce an estimate of the input signal to a two-dimensional spiking neuron model. This is a deterministic model of [http://www.selleckchem.com/products/MLN8237.html MLN8237 clinical trial] spike generation for auditory neurons in-vivo. dvdt=f(v)?w+I? (27) dwdt=a(bv?w) (28) I?(t)=C�Ҧ���0Th(��,��)s(t?��,��)d��?d��. (29) I? is an estimate of the input current signal and C is some constant. We shall attempt to fit this model to in-vivo extracellular spike train data using an evolutionary algorithm which is described in the next section. Our approach will be to use a tandem evolution method to alternately evolve the set of neuron parameters and the the set of STRF parameters for some number of iterations. This is illustrated in Figure ?Figure11 which shows a flowchart of the model and the optimization process. The three variable a2EIF model will not be used in the two stage auditory model because it presents [https://en.wikipedia.org/wiki/Aldosterone Aldosterone] a more challenging optimization problem, as will be shown later, and its parameters have not been well studied. Instead, the standard aEIF neuron will be used. Figure 1 Schematic of the flow of the STRF-Neuron cascade model optimization algorithm. The input stimulus, s(��, ��), is a spectro-temporal representation of a sound. It is convolved with a STRF, h, which forms the input to an aEIF neuron. The predicted ... 1.3. Optimization algorithm In this paper a genetic algorithm is used; it is customized to parameter discovery for the two stage spiking model. The genetic algorithm is a heuristic optimization method inspired by Darwinian evolution, first introduced in Holland (1973). The method starts with an initial population of parameter sets which represent potential solutions to the problem. The parameter sets in the population are ranked based on the fitness measure to be optimized, for example, how well a model predicts an experimental spike train.