1. A network comprising: a plurality of amplifiers A.sub.i each having an input node at which there is developed an input voltage U.sub.i, and each developing a non-inverting output V.sub.i and an inverting output -V.sub.i, with both of said outputs being related to said input by a sigmoid function g.sub.i ; means for applying input current I.sub.i to said input of each of said amplifiers A.sub.i ; a conductance network for connecting said positive and negative outputs to said inputs, said conductance network comprising conductance values selected for the nature of the decisional operation for which it is intended to minimize the energy function ##EQU4## where V.sub.i and V.sub.j are output voltages of said amplifiers A.sub.i and A.sub.j, respectively, T.sub.ij is a conductance that relates the amplified input voltage of amplifier A.sub.i, g(U.sub.i) to the input node of amplifier A.sub.j, R.sub.i is the equivalent resistance at said input of said amplifier A.sub.i and g.sub.i.sup.-1 is the inverse of g.sub.i ; and means for equalizing the speed of response of said amplifiers.