Since recently, neuronal-like spiking is predicted to emerge from fluidic iontronic circuits that employ ions in an aqueous environment as signal carriers. Initially tonic spiking in the form of a spike train was predicted, shortly after which we presented an alternative iontronic circuit that was also predicted all-or-none action potentials, as well as spike trains. These two modes of spiking are the typically the first to consider when studying neuronal signalling. However, our neurons exhibit a wide array of different spiking modes.
In our most recent publication in the journal Neuromorphic Computing and Engineering we propose a new theoretical circuit, based on our older work, from which various new modes of neuronal spiking emerge, on top of the aforementioned all-or-none action potentials and spike trains. These modes are phasic bursting, mixed mode spiking, tonic bursting (otherwise known as chattering), and threshold variability. In phasic bursting, a single burst of several spikes emerges upon applying a sustained stimulus, after which the system again settles to a steady state, despite the constant and sustained current stimulus. Mixed mode spiking consists of an initial burst of spikes upon a sustained stimulus, followed by tonic spiking. In tonic bursting, short periods of spiking, i.e. bursts, are interchanged by short periods of no spiking at all. Lastly, threshold variability indicates that the threshold for a neuron to spike can depend on the prior activity of the neuron. Therefore we considerably expanded the range of spiking modes proposed to emerge from iontronic fluidic circuits.
