> “Multiple simultaneous optimizers” search for a (local) maximum value of some function E(λ1, …, λn) of several parameters. Each unit Ui independently “jitters” its parameter λ1, perhaps randomly, by adding a variation δi(t) to a current mean value μi. The changes in the quantities λi and E are correlated, and the result is used to slowly change μi. The filters are to remove DC components. This technique, a form of coherent detection, usually has an advantage over methods dealing separately and sequentially with each parameter.
The link has been already provided above (opus cit), it's directly connected to the very question of gradients, providing a specific implementation (it even comes with a circuit diagram). As you were claiming a lack of detail (but apparently not honoring the provided citation)…
(The earlier you go back in the papers, the more specifics you will find.)
vague esssay without specifics