Following on the previous post, with the analog-digital analogy often comes the idea that the relation between rates and spikes is that of an analog-digital conversion. Or spikes are seen as an analog-digital conversion from the membrane potential. I believe this comes from the evolutionary argument that it seems that spikes appeared for fast propagation of information on long distances, and not because there is anything special about them in terms of computation. It is quite possible that this was indeed the evolutionary constraint that led to the appearance of action potentials (although this is pure speculation), but even if this is true, the reasoning is wrong: for example, the ability of humans to make tools might have developed because they stood up. Yet standing up does not explain tool-making at all. So standing up allows new possibilities, but these possibilities follow a distinct logic. Spikes might have appeared primarily to transmit information at long distances, but once they are there, they have properties that are used, possibly for other purposes, in new ways. In addition, that they appeared to transmit information and the information was analog does not mean information is now used in the same way. Consider: to transmit information over long distances, one uses Morse code on the telegraph. Do you speak to the telegraph? No, you change the code and use a discrete code that has little connection with the actual sound wave. Finally, even if all this makes sense, it still is not an argument in favor rate-based theories, because rate is an abstract quantity that is derived from spikes. So if we wanted to make the case that spikes are only there to carry a truly analog value, the membrane potential, then it would lead us to discard spikes as a relevant descriptive quantity, and a fortiori to discard rates as well. From a purely informational viewpoint (in the sense of Shannon), spikes produced by a neuron carry less information than its membrane potential, but rate carries even less information, since it is abstracted from spikes.