Topology and dynamics of the canonical circuit of cat V1

The neocortex is a major component of the most sophisticated and economically significant computer in existence, nevertheless the organisation and operation of its computational circuit is not yet understood. Here we make some steps toward relating anatomical structure to computational function. We use methods of quantitative neuroanatomy to estimate the cortical circuit by defining the projection matrix between the various cells types of the neocortex of the cat, and then we consider the implications of this connectivity for cortical signal processing. Our analyses show that for a reasonable choice of the ratio between excitatory and inhibitory efficacy, the overall cortical circuit lies near the border of dynamical stability. We discuss a model of co-operative competitive processing that is consistent with the observed connectivity in the superficial layers of the cortex, and consider also how the topology of the overall cortical circuit could be configured dynamically through average inhibition. (C) 2009 Elsevier Ltd. All rights reserved.