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Experiment: Spikes

This is a great introductory experiment to get you started with spikes!


Your brain uses a combination of chemicals and electricity to operate. Brain Cells (neurons) need to communicate with each other to control your body. A brain with only 1 neuron is not a brain.

Exp 1 single neuron.jpg
Exp 1 neurons together.jpg

A brain is a network (friendship) of neurons. Your brain has and uses around one hundred billion neurons! But how do all of these neurons talk to each other? One of the the first ways cells used to network was chemical communication.

Exp1 fig2.jpg

Bacteria use this method. It works well, but is limited by diffusion. For example, when you fart, how long does it take for someone on the edge of the room to smell it? There should be a faster way. One way is to bring cells closer together through stretching.

Exp1 fig3.jpg

But there is still a problem. The signal still needs to travel a long way through the cell. Is there a way to make this faster? What is very fast & important today?

Exp1 fig4.jpg

Electricity! Notice how fast the lights in your house turn on when you flick the switch. Neurons use electricity as well; electrical pulses travel down the neurons This pulse is called the

Exp1 spike.jpg

We at Backyard Brains have dedicated our lives to studying spikes, and you can too! But first, some biology. 380 million years of evolution bring you the cockroach. We will use the Discoid cockroach (Blaberus discoidalis), or false death’s head. They live in the Amazon rainforest of South America under the bark of rotting trees.

Exp 1 Fig 6-cockroach.jpg

Like all animals (beyond creatures like sea sponges), cockroaches’ bodies are filled with nerves to control movement & sensation, among many other things. Let’s begin.

Here is a video showing spiking activity.


  1. Take a cockroach & put it in a jar of ice water. Wait a few minutes until it stops moving.
    Exp1 cockroachhoodie.jpg
  2. Remove the cockroach, and cut off one of his legs near the body, so that you end up with a leg like this:
    Exp 1 Fig. 8-cut leg cockroach.jpg
    Exp 1 Fig. 9-roach leg.jpg
  3. Put some petroleum jelly (or low temp wax) on the exposed wound of the leg & accompanying spot on the cockroach body. Return Cockroach to its house. It'll be fine, the leg will grow back if the cockroach is not a full grown adult yet (Adults have wings, nymphs don't).
  4. Place the leg on the cork of your SpikerBox, allowing a bit of the leg to overhang, like this:
    Exp1 fig10.jpg
    And put the two electrodes in:
    Exp1 fig11.jpg
  5. Turn your SpikerBox on! If you hear a popcorn sound, congratulations, you have just heard your first neuron!
  6. Now let's see what the electrical discharge looks like. Plug your sound cable from the SpikerBox into your iPhone or into the microphone input of your computer.Turn on “Backyard Brains” (iPhone) or Audacity (laptop). You should see:
Exp1 spikes.jpg
Zoom in, & the spikes look like:
Exp1 closeupspike.jpg
This is due to ion channels opening and closing in the neurons, causing the pulse.

Update: You can also do this same experiment on cricket legs if you can't find cockroaches. See video below.

Educational Standards

The above lesson plan meets the following Society for Neuroscience’s Core Concepts. These core concepts are themselves cross-referenced with the National Research Council’s National Science Education Standards

Core Concepts Covered in this Lesson Plan
1.a. There are a hundred billion neurons in the human brain, all of which are in use.
1.b. Each neuron communicates with many other neurons to form circuits and share information.
2.a. Sensory stimuli are converted to electrical signals.
2.b. Action potentials are electrical signals carried along neurons.
2.c. Synapses are chemical or electrical junctions that allow electrical signals to pass from neurons to other cells.
8.a. Experiments on animals play a central role in providing insights about the human brain and in helping to make healthy lifestyle choices, prevent disease, and find cures for disorders.
This page was last modified on 1 December 2012, at 03:49.