Control of firing mode in nonlinear neuron circuit driven by photocurrent

Abstract

Firing patterns discern the electrical activities in biological neurons when intracellular and extracellular ions are pumped into cells and exchanged there. Artificial neural circuits can be tamed to reproduce similar firing modes from biological neurons by applying appropriate physical stimuli. Photocurrent generated in the phototube can be used as a signal source, which can stimulate the neural circuits, while the involvement of which branch circuit will be much different because the channel current can control the dynamics of functional neuron to a different degree. In this paper, based on a nonlinear (FitzHugh-Nagumo, FHN) neural circuit composed of one capacitor, induction coil, nonlinear resistor, two ideal resistors and one periodical stimulus, the phototube is incorporated into different branch circuits for changing the channel current and the biophysical role of photocurrent is investigated. The dynamical equations of three types of system are unified, though they fall in different areas in parameter space. The membrane potential can be directly changed and firing modes are switched when photocurrent is activated to change the channel current by connecting the phototube to the capacitor. The induced current across the induction coil is regulated to balance the external stimulus when the phototube is connected to the induction coil in series. The two types of photosensitive neuron models constructed in this paper are compared with the photocurrent driven inductive branch showing that the photocurrent driven capacitive branch can very effectively regulate the membrane potential and greatly improve the photosensitive sensitivity.