Fig. 1

A schematic presentation of the homeostatic plasticity mechanism. a. Reduced inhibition (I) and/or enhanced excitation (E) that leads to hyperexcitability is a widely accepted mechanism of acquired epilepsy. b. We propose that the brain needs to not only maintain a balance between E and I, but also maintain a set level of functional output (i.e. neuronal activity, represented here as filling the circle). c. Injuries and other brain pathologies cause loss of neurons and neuronal activity (dotted circle). To compensate for the lost function, the neural network would use the homeostatic plasticity mechanism to scale up excitation (E) (and may simultaneously reduce inhibition (I)) to attempt to reach a set level of neuronal activity, which causes hyperexcitability simultaneously. d. Controlling hyperexcitability may be achieved by stimulating neuronal activity after injuries or degeneration, which will promote functional recovery and suppress intrinsic homeostatic activity regulation, and increase activity-dependent enhancement of inhibition