Introduction

In neuroscience there has been considerable research into how the neural system attains its characteristics and capabilities. In a neuron, membrane potential is controlled by the inflow and outflow of ions. In fact, the triggering of the action potential is caused when ions flow in or out of the neuron. This in turn changes the potential across the cell. This type of interaction can be modeled in an electrical equivalent circuit using a battery, resistor and a capacitor. The battery represents the stored potential that is maintained across the ion channels and the resistor represents the quantity of ions that are allowed to flow in or out of the cell. Capacitor represents the intracellular and extracellular solutions, separated by the non-conducting membrane. When more ion channels are opened, the more ions flow. In other words, the resistance to flow for the ions is decreased, conductance is increased, by having more ion channels open. So the passive transports or ion channels are basically just variable resistors.

We have developed hardware neuron models to study real-time processing of information flow using a bursting neuron model.

Objective

• Study the characteristics of bursting neurons.

Theory

A neuron is frequently compared to electronic circuit as most of its properties can be modeled as electronic circuits. The membrane potential across the neuronal membrane is similar to the voltage of an electrical circuit. In neurons, this is known as potential difference which is due to the effects of charges across the membrane. Separation of charge is termed as voltage.  In electrical circuits, voltage is acquired using a power source. The electrical circuit expresses current as it (current) is the movement of charges from one point to other point. In the neurons this affect is caused by movement of charged ions across cell membrane. 

In this experiment, we modeled neuron as RC networks. Neuronal membrane has capacitive and resistive properties. Thus it often referred to as membrane resistance or membrane conductance. Membrane resistance is too high when most of the ion channels are closed. At this time few ions crosses the membrane.  On the other hand, during depolarization events,  in which many ion channels are open and the cell experiences large influxes and effluxes of ions, membrane conductance is said to be high. A capacitor consists of two conducting regions separated by an insulator. It works by accumulating a charge on one of the conducting surfaces. Electric fields are created as this charge builds. This field pushes charges on the other side of the insulator away. Similarly in the neuron the membrane is the insulator between the two conducting intra and extracellular fluids. Capacitance plays the most important role in action potential generation and propagation.

                Figure.1.a                                                                                                                   Figure.1.b  

Figure.1.a. Schematic cartoon of neuron along with (The cartoon mechanism of a biological neuron showing stimulating electrode in the response electrode. Response electrode records the output behavior and stimulating electrodes provides the input)

Figure.1.b. RC properties

Bursting is an extremely diverse general phenomenon of the activation patterns of neurons in the central nervous system and spinal cord where periods of rapid spiking are followed by quiescent, silent, periods. Bursting Hardware neuron model with the simple excitable hardware neuron model.

We adopted the above mentioned RC circuit to generate burst phenomenon. We applied pulses at regular intervals to the RC circuit to create the burst .The pulses with time intervals  will charge and discharge capacitors at regular intervals which may leads to the series of action potentials at regular intervals Since the models with adaptation, reproduce both spiking and bursting.