Temporal differentiation and the optimization of system output
  This paper develops a set of simplified dynamical models with which to explore the conditions under which temporal differentiation leads to optimized system output. By temporal differentiation, we mean a division of labor whereby different subtasks associated with performing a given task are done at different times. The idea is that, by focusing on one particular set of subtasks at a time, it is possible to increase the efficiency with which each subtask is performed, thereby allowing for faster completion of the overall task. For this paper, we consider a process whereby some resource is converted into some final product in a series of three agent-mediated steps. Temporal differentiation is incorporated by allowing the agents to oscillate between performing the first two steps and performing the last step. We find that temporal differentiation is favored when the number of agents is small, and when the process intermediates have a much longer lifetime than the original resource. Within the framework of biological systems, we argue that these results provide a possible evolutionary basis for the emergence of sleep, and also of distinct REM and non-REM sleep states. We also discuss our use of a three-step model. Briefly, in order for temporal differentiation to increase product output in a mean-field description of resource metabolism, it is necessary for temporal differentiation to have a nonlinear effect on individual process rates. For stochastic models, we argue that temporal differentiation can increase product output even in fundamentally linear systems. 
Emmanuel Tannenbaum