The authors derive optimal monotonic tuning functions under metabolic constraints by reformulating the problem as a constraint optimization problem, which apparently can be solved in closed form. Overall, the paper is of very high quality, but it is too dense and covers too much material for a 8 page NIPS paper. Before I make some more specific comments, I would urge the authors to focus on the single neuron/pair of neuron cases for this paper and leave the population analysis for a later publication or a extended journal version. The population part is only sketched in the paper and I am not quite sure if I understand the results and implications (also, there is no figure for this part, which doesn't help understanding it better). Specific comments: Equations 3 and 4: I am not sure I understand how equation 4 is a special case of equation 3. Figures 1-3: I find those figures very hard to parse.