1. A parallel-circuit signal processing device comprising a series of N integrative units U.sub.j, each constructed to respond to the jth component of an N-dimensional input vector, to produce a time varying output signal O.sub.j, a multiplexer for sequentially sampling the O.sub.j values in each of the N receptor units, means storing a matrix of k.sub.ee.sup.jk coupling coefficients relating the output signal coupling between pairs of U.sub.j, U.sub.k units in the device, means for calculating, for each O.sub.j value sampled by said multiplexer, feedback input signals which relate the just-sampled O.sub.j value and the k.sub.ee.sup.jk coupling coefficients between U.sub.j and other units in the device, and a demultiplexer for applying, following each O.sub.j value sampled by the multiplexer, the feedback signals just calculated on the basis of the sampled O.sub.j value, to each of the corresponding units U.sub.k.