Ion channel degeneracy enables robust and tunable neuronal firing rates.
Firing rate is an important means of encoding information in the nervous system. To reliably encode a wide range of signals, neurons need to achieve a broad range of firing frequencies and to move smoothly between low and high firing rates. This can be achieved with specific ionic currents, such as A-type potassium currents, which can linearize the frequency-input current curve. By applying recently developed mathematical tools to a number of biophysical neuron models, we show how currents that are classically thought to permit low firing rates can paradoxically cause a jump to a high minimum firing rate when expressed at higher levels. Consequently, achieving and maintaining a low firing rate is surprisingly difficult and fragile in a biological context. This difficulty can be overcome via interactions between multiple currents, implying a need for ion channel degeneracy in the tuning of neuronal properties.
Biology Department and Volen Center, Brandeis University, Waltham, MA 02454.
Guillaume
G
Drion
Biology Department and Volen Center, Brandeis University, Waltham, MA 02454.
Timothy
T
O'Leary
Biology Department and Volen Center, Brandeis University, Waltham, MA 02454 marder@brandeis.edu.
Eve
E
Marder
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D006801:Humans; D007473:Ion Channels / Q000737:chemistry*; D007477:Ions; D008564:Membrane Potentials / Q000502:physiology; D008959:Models, Neurological; D009474:Neurons / Q000502:physiology*; D011188:Potassium / Q000737:chemistry; D015221:Potassium Channels / Q000737:chemistry
D007473:Ion Channels; D007477:Ions; D015221:Potassium Channels; D011188:Potassium
FI curve; Type I excitability; Type II excitability; bifurcation; reduced neuron model