Homeostatic plasticity of excitability in crustacean central pattern generator networks

- Plasticity of excitability is a key mechanism for homeostatic control of output.
- Activity-dependent feedback is a key regulator of plasticity of excitability.
- Neuromodulation can affect excitability over longer-term time scales.
- Changes in activity and excitability are associated with correlated channel mRNAs.
- The implications of plasticity for cell-to-cell variability are discussed.

Plasticity of excitability can come in two general forms: changes in excitability that alter neuronal output (e.g. long-term potentiation of intrinsic excitability) or excitability changes that stabilize neuronal output (homeostatic plasticity). Here we discuss the latter form of plasticity in the context of the crustacean stomatogastric nervous system, and a second central pattern generator circuit, the cardiac ganglion. We discuss this plasticity at three levels: rapid homeostatic changes in membrane conductance, longer-term effects of neuromodulation on excitability, and the impacts of activity-dependent feedback on steady-state channel mRNA levels. We then conclude with thoughts on the implications of plasticity of excitability for variability of conductance levels across populations of motor neurons.