Wherefore Art Thou, Homeo(stasis)? Functional Diversity in Homeostatic Synaptic Plasticity
Figure 1
Closed-loop control in homeostatic regulation. In closed-loop control systems, observed activity values (a) are compared to a desired set point (yellow star) (b) and deviations are registered as errors (c). The homeostatic response program is calculated and initiated in response to the error signal (d). Many control strategies are possible, including proportional-integral (PI) control (left) and bang-bang control (right). PI control: PI controllers compute a compensatory response as a function of the properties of the error, namely, the proportional (orange, magnitude at indicated with arrow) and integral (purple, cumulative error over time) components of the deviation. A variation of this regulation, the proportional-integral-derivative (PID) controller, also incorporates a derivative component that detects the rate of change of the deviation (green bar in activity trace, ). The initiated response is therefore tailored to the immediate degree of deviation from the set point (proportional), the cumulative magnitude of the deviation (integral), and the rate of change of the deviation (derivative). Bang-bang control: Bang-bang control consists of set compensatory responses which are initiated once a threshold is crossed (blue lines) and halted once the activity value returns to the acceptable range of values.
