Bayesian Regularized Neural Networks for Small n Big p Data

Artificial neural networks (ANN) mimic the function of the human brain and they have the capability to implement massively parallel computations for mapping, function approximation, classification, and pattern recognition processing. ANN can capture the highly nonlinear associations between inputs (predictors) and target (responses) variables and can adaptively learn the complex functional forms. Like other parametric and nonparametric methods, such as kernel regression and smoothing splines, ANNs can introduce overfitting (in particular with highlydimensional data, such as genome wide association -GWAS-, microarray data etc.) and resulting predictions can be outside the range of the training data. Regularization (shrinkage) in ANN allows bias of parameter estimates towards what are considered to be probable. Most common techniques of regularizations techniques in ANN are the Bayesian regularization (BR) and the early stopping methods. Early stopping is effectively limiting the used weights in the network and thus imposes regularization, effectively lowering the Vapnik-Chervonenkis dimension. In Bayesian regularized ANN (BRANN), the regularization techniques involve imposing certain prior distributions on the model parameters and penalizes large weights in anticipation of achieving smoother mapping.