Top-Down Connections in Self-Organizing Hebbian Networks: Topographic Class Grouping
We investigate the effects of top-down input connections from a later layer to an earlier layer in a biologically inspired network. The incremental learning method combines optimal Hebbian learning for stable feature extraction, competitive lateral inhibition for sparse coding, and neighborhood-based self-organization for topographic map generation. The computational studies reported indicate top-down connections encourage features that reduce uncertainty at the lower layer with respect to the features in the higher layer, enable relevant information to be uncovered at the lower layer so that irrelevant information can preferentially be discarded [a necessary property for autonomous mental development (AMD)], and cause topographic class grouping. Class groups have been observed in cortex, e. g., in the fusiform face area and parahippocampal place area. This paper presents the first computational account, as far as we know, explaining these three phenomena by a single biologically inspired network. Visual recognition experiments show that top-down-enabled networks reduce error rates for limited network sizes, show class grouping, and can refine lower layer representation after new conceptual information is learned. These findings may shed light on how the brain self-organizes cortical areas, and may contribute to computational understanding of how autonomous agents might build and maintain an organized internal representation over its lifetime of experiences.
top-down connections self-organization hebbian learning autonomous feature extraction deep networks