Figure 5. Model is robust to training set size (PoE model).

The PoE model has approximately degrees of freedom. However, for computational reasons, we trained the model with only training examples (each training example is projected onto 150 principal components). We therefore examined the effect of increasing the training set size (for the case of normal input). The receptive field orientation selectivity was robust to changes in training set size. There was also no obvious visual change in receptive field structure (data not shown). This demonstrates that the sparsity constraints result in receptive field formation robust to training set size.