Sparse, Geometric Autoencoder Models of V1
This work addresses a specific problem in computational neuroscience for modeling V1 visual cortex, representing an incremental improvement over existing sparse coding methods.
The authors tackled the mismatch between classical sparse coding models and observed primate simple cell receptive fields by proposing an autoencoder with structured sparsity, resulting in artificial neurons better matched to primate data.
The classical sparse coding model represents visual stimuli as a linear combination of a handful of learned basis functions that are Gabor-like when trained on natural image data. However, the Gabor-like filters learned by classical sparse coding far overpredict well-tuned simple cell receptive field (SCRF) profiles. A number of subsequent models have either discarded the sparse dictionary learning framework entirely or have yet to take advantage of the surge in unrolled, neural dictionary learning architectures. A key missing theme of these updates is a stronger notion of \emph{structured sparsity}. We propose an autoencoder architecture whose latent representations are implicitly, locally organized for spectral clustering, which begets artificial neurons better matched to observed primate data. The weighted-$\ell_1$ (WL) constraint in the autoencoder objective function maintains core ideas of the sparse coding framework, yet also offers a promising path to describe the differentiation of receptive fields in terms of a discriminative hierarchy in future work.