Table 1.

Proposed relationship between a control theoretic framework and the optimization of energy use in the brain over time.

Control theory	Variable	Interpretation
Time index	k	Index of time in a scale in which distinct control actions are possible
State	xk = [HN, HA]	Quantity of energy available to neurons and astrocytes
Control	u	Neuromodulator concentration driving neural recruitment in an area
Dynamics	xk + 1 = f(xk, uk)	Energy dynamics in the brain
Objective function	g(xk, uk)	Combination of cognitive costs (if any) and rewards for a single time step
Objective function	J	Overall objective function to be optimized over a given time horizon