By Greg Gage
The human brain has more than 100 billion cells called neurons. These cells allow us to sense and communicate with the outside world. They are also responsible for neurological diseases that will affect one out five of us, yet we still don’t have cures. While you may often read about the brain, do you actually know how it works? Chances are you haven’t studied neuroscience directly.
Studying the brain is difficult to do. The brain activity is electrical and chemical and therefore can be understood only while the brain tissue is still alive. The brain is quite different from other organs, such as the heart, which is a muscle. You could look at a plastic model of the heart to understand how it functions (it is a pump), but a plastic model of the brain doesn’t tell you anything about how it works. In mammals, the brain is protected by a thick skull, which makes getting to it quite difficult. And even if you could get to it easily, the equipment to measure the brain’s electricity typically cost tens of thousands of dollars.
Wouldn’t it be great if you could explore the wonders of the brain by doing neuroscience experiments in your own home? This article will show you how to do just that! By using kits you can build yourself, some insects from around your house, and your smartphone, iPad, or a computer, you will be able to understand many of the basic principles of how neurons encode information.
First, let’s discuss some background on neurons. In the nervous system, neurons are special cells that consist of a body, dendrites, and a long axon. Axons are nerve fibers through which the neuron sends electrical impulses (called “action potentials” or “spikes”) from the cell body all the way to another neuron. When the action potential reaches the end of an axon, a chemical message gets sent to the next cell across the small space between them (called the “synapse”). On the other side of the synapse lies the dendrite of the next cell. The dendrite receives these chemicals, which then change the amount of electricity inside of the cell body. Once the electricity is high enough, they send off a spike and the process continues. Human and insect neurons are remarkably similar in their build and function, which allows us to use insects to understand how the human brain works.
Recording electrical messages from bugs is much easier than recording electrical messages from the human brain, because bugs have a hard but thin exoskeleton (shell). By placing metal pins inside an insect, you can amplify these small spikes and “listen” to what the brain sounds like. An affordable bio-amplifier costs ~$100 and can also be used to send the audio of the brain signals into your iPad, PC, or smartphone (Android or Apple). Once hooked up to a device, you will be able to observe these electrical messages as they travel down the axons in real time. In a series of easy experiments using a leg of a cockroach, you can not only hear and see the action potentials, but you can also learn how they encode information!
The first experiment is easy. You can use the Americana periplaneta (American cockroach), Blaberus discoidalis (discoid, or false death’s head), or Gromphadorhina portentosa (Madagascar hissing cockroach). These species are large, easy to handle, easy to maintain, and available from many pet stores as a feeder insect.
Let’s get started. First we put a cockroach in some ice water to anesthetize it. Insects are cold-blooded. So when we place the bug into cold water, the neurons stop firing. Therefore the bug will stop moving and it won’t feel pain. If you ever had a shot at the dentist’s office before getting a tooth drilled, you know how quieting the neurons works. Once the insect is out cold . . . we cut one of its legs. The legs grow back; don’t worry! We need the leg to warm back up to room temperature so that we can record its neurons.
Every cockroach leg has many, many hairs on it, and under each of these hair lies a neuron. These neurons send electrical information (spikes) to the brain about things that happen in the cockroach’s surroundings, such as wind, touch, or vibrations of someone approaching. We can record spikes from these neurons by sticking two metal pins into a leg that we place on a cork. There are so many axons in the leg that when we place a pin randomly in the leg it will be touching one of them.
Once you turn on the device, you can begin to hear what these spikes sound like. People describe this sound as being similar to the sound of rain or popcorn popping. If you then import the sound into your iPad, you can look at the shape of the spikes you are listening too. You will notice that spikes take on a very distinct down-up-down waveform. The size of this waveform (the amplitude) never changes. What does change is the rate at which these spikes travel down the axon. This is how the brain encodes information.
We can do an experiment to see how this works. Remember that we said these neurons send information about touch or wind. By gently blowing on the leg or touching the hairs of the leg with a toothpick, you will notice a change in the rate of spikes. This is known as “rate coding,” which means that as the intensity of touching increases, the frequency (rate) of action potentials also increases. You can test this directly by observing the spikes as you vary the amount of pressure on the barbs.
There are many more experiments you can perform to understand more about how the brain works. For example, you can carry out experiments to learn how the chemical synapses work, how electricity allows our muscles to move, how temperature affects neurons, and how to communicate with the nervous system using electricity. We hope you get started with your exploration today.
If you like learning about the brain, you may like to learn more about becoming a neuroscientist. While we know a lot about how the brain works, there are still many questions that remain unanswered, such as these: How do we perceive consciousness? Why do we sleep? and How can we prevent brain diseases? Having more people looking at these questions can help us understand the brain more quickly!
Greg Gage is a DIY Neuroscientist and cofounder of Backyard Brains, an educational neuroscience company that manufactures low-cost neuroscience kits for amateurs and students. With their SpikerBox kits, you too can do neuroscience experiments, right from your own home. Visit backyardbrains.com for more videos and details.
Copyright 2012, used with permission. All rights reserved by author. Originally appeared in the May 2012 issue of The Old Schoolhouse® Magazine, the family education magazine. Read the magazine free at www.TOSMagazine.com or read it on the go and download the free apps at www.TOSApps.com to read the magazine on your mobile devices.