Visual cortex operations and their implementation using the incoherent optical neuron model

The incoherent optical neuron model uses two different device responses, an inhibitory response and a nonlinear output response, to realize a complete neuron unit that has both inhibitory and excitatory inputs. We describe its use to implement a model of simple cells of the visual cortex. Such simple cells perform the operations of edge detection, orientation selection, and in the case of moving objects, direction and speed selection. Experiments are described that utilize two Hughes liquid-crystal light valves to perform the functions of input transduction and optical neuron unit-array implementation. A multiplexed dichromated gelatin hologram serves as a holographic optical element that forms space-invariant (but otherwise arbitrary) point-spread functions for the network interconnections. Changing the holographic interconnection pattern permits implementation of different simple cells performing, e.g., transient response, edge detection, orientation preference, and direction and speed preference. Experimental results of these operations are presented.