Emergence of conjunctive visual features by quadratic independent component analysis
Jussi Lindgren and Aapo Hyvärinen
In: NIPS 2006, 4-7 December 2006, Vancouver, Canada.
In previous studies, quadratic modelling of natural images
has resulted in cell models that react strongly to edges and bars.
Here we apply quadratic Independent Component Analysis to natural
image patches, and show that up to a small approximation error,
the estimated components are computing conjunctions of two linear
features. These conjunctive features appear
to represent not only edges and bars, but also inherently two-dimensional
stimuli, such as corners. In addition, we show that for many of
the components, the underlying linear features have essentially V1 simple
cell receptive field characteristics.
Our results indicate that the development of the V2 cells preferring
angles and corners may be partly explainable by the principle of
unsupervised sparse coding of natural images.