Contribution of lateral interactions in V1 to organization of response properties.

ABSTRACT

We propose a model of self-organization of synaptic connections in V1, emphasizing lateral interactions. Subject to Hebbian learning with decay, evolution of synaptic strengths proceeds to a stable state in which all synapses are either saturated, or have minimum pre/post-synaptic coincidence. The most stable configuration gives rise to anatomically realistic "local maps", each of macro-columnar size, and each organized as Mobius projections of retinotopic space. A tiling of V1, constructed of approximately mirror-image reflections of each local map by its neighbors is formed, accounting for orientation-preference singularities, linear zones, and saddle points-with each map linked by connections between sites of common orientation preference. Ocular dominance columns are partly explained as a special case of the same process. The occurrence of direction preference fractures always in odd numbers around singularities is a specific feature explained by the Mobius configuration of the local map. Effects of stimulus velocity, orientation relative to direction of motion, and extension, upon orientation preference, which are not accounted for by spatial filtering, are explained by interactions between the classic receptive field and global V1.