Interesting, I always wondered if there were differences like that. The way I'd think of that if I were translating it to circuitry would be to say that the mammalian brains operate at saturation of a transistor (fully on, or fully off). And that C. elegans would then be operating in the linear region of the transistor; assuming that you could represent each neuron as a transistor of course. I wonder if the change in structure happened roughly for the same reason that we're changing much of our circuitry from analog to digital (or at least avoiding analog as much as possible) because we can get better noise response and simpler circuit design. Makes me wonder then if something like epilepsy could be caused by some neurons operating the wrong way and not giving clear signals down the chain which could lead to feedback and/or noise that ends up detrimental.

Does this mean that one neuron can carry a signal that is more dense in data than a 0/1 binary spiking signal? Like a single neuron can transmit a complex feeling instead of just if it's touching something or not?