Emanuel Todorov, Athanassios Siapas, David Somers
A general feature of the cerebral cortex is its massive intercon(cid:173) nectivity - it has been estimated anatomically  that cortical neurons receive upwards of 5,000 synapses, the majority of which originate from other nearby cortical neurons. Numerous experi(cid:173) ments in primary visual cortex (VI) have revealed strongly nonlin(cid:173) ear interactions between stimulus elements which activate classical and non-classical receptive field regions. Recurrent cortical con(cid:173) nections likely contribute substantially to these effects. However, most theories of visual processing have either assumed a feedfor(cid:173) ward processing scheme , or have used recurrent interactions to account for isolated effects only [1, 16, 18]. Since nonlinear sys(cid:173) tems cannot in general be taken apart and analyzed in pieces, it is not clear what one learns by building a recurrent model that only accounts for one, or very few phenomena. Here we develop a relatively simple model of recurrent interactions in VI, that re(cid:173) flects major anatomical and physiological features of intracortical connectivity, and simultaneously accounts for a wide range of phe(cid:173) nomena observed physiologically. All phenomena we address are strongly nonlinear, and cannot be explained by linear feedforward models.