Criticality of lateral inhibition for edge enhancement in neural systems

Although the role of lateral inhibition in edge (contrast) enhancement is well known, it has not been parametrized. This paper investigates the imbalance between the lateral inhibitory and excitatory stimuli and its effect on the edge enhancement and stability. It is shown that this imbalance can be expressed through γγ, a ratio of inhibitory to excitatory weights in a neuron. Stability requires γγ to be less than the critical ratio  ΘΘ. As γγ approaches ΘΘ, edge enhancement increases, the rise being the sharpest just before instability. The increase in edge enhancement is also accompanied by an increase in the lateral spread of perturbations across the neuron layer.