Action potential experiments

Encoding stimulus strength

We know that we need to inject a certain amount of current, which we will call stimulus strength, in order to elicit an action potential from a neuron. In reality, the ability of a neuron to fire an action potential does not only depend on stimulus strength, it also depends on stimulus duration. This is because the neuron's membrane potential has the ability to integrate its inputs over time, until it reaches the threshold potential to fire an action potential.

Once we have a stimulus strength and duration that is capable of eliciting an action potential from a neuron, how does further increasing the strength, while keeping the duration constant, affect action potentials? In the previous experiments we saw that action potentials do not get bigger, they always have the same size. So can we infer stimulus strength from a neuron's action potentials at all? The answer is that stimulus strength is reflected in the firing rate of the neuron, i.e. how many action potentials the neuron generates in a certain window of time.

In this simulation we will have a constant stimulus duration of 15 ms and we will vary the stimulus strength.

Multiple action potentials