A simple model for development and function of long-range connections in neocortex
We present a model for the development of long-range horizontal connections in cortex. Fixed short-range interactions with local excitatory feedback and an inhibitory surround induce localized attractors (‘activity blobs’) that depend sensitively on small variations of the input. This provides the basic mechanism for the putative role of the long-range horizontal connections: to switch between different attractors and to organize rapidly the grouping of distant neurons. We show that Hebbian adaptation of sparse long-range horizontal connections under these conditions is sufficient to break the initial symmetry of homogeneous connectivity. This can induce a strong dependency of the local responses on the input from outside the classical receptive fields. This grouping mechanism may explain a wide range of physiological and psychophysical observations.