NONLINEARITIES WITHIN THE CAT LGN CELL RECEPTIVE-FIELDS IN SIMULATED NETWORK WITH RECURRENT INHIBITION

We investigated the receptive fields of principal cells from the cat's lateral geniculate nucleus cells. About 20% of the X type neurones sh owed clear nonlinearities of summation when stimulated by two simultan eously onset, small bars of light. The possible source of this nonline arity was studied on a specially designed model of a one-layer neurona l network with inhibitory, recurrent interactions, intended to mimic t he inhibitory influence exerted on geniculate relay cells by perigenic ulate interneurones. The model, when activated from periphery by two s timuli-like input patterns, produced at the output side the nonsymmetr ical profiles of the receptive fields sensitivity, similar to those ob tained in real experiments. This nonlinear output appeared when some o f the relay cells were inhibited below their firing level threshold an d this effect was spread through the network by lateral inhibitory con nections. It is concluded that physiologically observed nonlinearities of the order of single receptive field mechanisms can be predicted by a simple recurrent network.