Fig. 1.

Computation costs little compared to communication. Communication alone accounts for more than two-thirds of the available 4.94 ATP-W (Table 1), with slightly more consumption due to WM than to GM (big pie chart). Computation, the smallest consumer, is subpartitioned by the two ionotropic glutamate receptors (bar graph). $SynMo{d}^{+}$ includes astrocytic costs, process extension, process growth, axo- and dendro-plasmic transport of the membrane building blocks, and time-independent housekeeping costs (although this last contributor is a very small fraction). The small pie chart subpartitions GM communication. See Results and Materials and Methods for details. WM communication includes its maintenance and myelination costs in addition to resting and action potentials.