Bernal Jimenez edited section_Descending_the_Alternate_Sparse__.tex  about 8 years ago

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\section{Descending the Alternate Sparse Coding Objective}\label{descend}  The original SAILnet paper \cite{Zylberberg_2011} maintains the reconstruction part of the sparse coding objective but instead of L1 regularization, the sparse prior was turned into a set of two constraints: homeostasis for the individual neuron's firing rates and decorrelation for the pairwise statistics:  \begin{equation} \begin{equation}\label{eq:1}  E(X, a; \Phi, W, \theta) = \frac{1}{2}\sum_i(X_i-\sum_j\Phi_{ij}a_j)^2 + \sum_i\theta_i(a_i-p) + \sum_{ij}W_{ij}(a_ia_j-p^2)  \end{equation}  The original sparse coding reconstruction term in \ref{eq:1} will lead to both non-local learning rules for $\Phi$ and a non-local inference circuit. So, it is approximated by an objective which will lead to Oja's learning rule rule:  \begin{equation}\label{local}  E(X, a; \Phi, W, \theta) = \frac{1}{2}\sum_{ij}(X_i-\Phi_{ij}a_j)^2 + \sum_i\theta_i(a_i-p) + \sum_{ij}W_{ij}(a_ia_j-p^2).  \end{equation}