[orbifold]

- Weights are adjusted at the end of the backward in time (adjoint) integration, according to the weight gradients accumulated at pre-spike times.

- We only consider one kind of model system in this paper but this method would work for any kind of hybrid dynamical system, so also other physical substrates (a lot of exciting work to do there).

- We used to sell a neuromorphic hardware system Spikey for ~3000 Euro (basically at cost), we've recently completed a similar project, we also provide access to remote users via the ebrains collaboratory (https://ebrains.eu/service/collaboratory/). There are a number of commercial offers in the works (SynSense, Inatera). You can also buy SpiNNaker boards or access them via ebrains. Loihi and TrueNorth either don't sell or are pretty expensive, but they have "research agreements" in place.