Experiment: Rate Coding
You’ve heard the spikes; but what do they do? The spikes are a way of neurons communicating with each other. The simplest way is with rate, or number of spikes per second. We will discover this property of neurons today. What you need are:
- your breath
- a toothpick
Background
Cockroaches’ legs are covered with barbs that can detect wind and other movements, much like your cats’ whiskers. These barbs tell the cockroach whether the wind is blowing, how fast, and in what direction!. Let’s do a simple experiment.
Procedures
- Turn on the SpikerBox with the leg attached like you did in the last experiment.
- Blow lightly on the leg. Did you hear anything?
- Blow vigorously on the leg. Is there any difference?
Each thorn on the leg is innervated by a nerve:
The more the thorn moves, the more the neuron fires! This is called “rate-coding.”
Let’s take another look with a method that is easier to control than your breath. Taking your small toothpick, lightly touch each barb until you find one that causes the loudest, most vigorous change in spikes. Touch the barb in different directions, with varying degrees of pressure. Do you notice anything? We will return to this in the experiment on Somatotopy.