Experiment: Principles of NeuroProsthetics
One of the exciting developments of the first decade of the 21st century has been improvements in neuroprosthetics! But, you, may ask, what are neuroprosthetics? A neuroprosthetic is a device that replaces the function of a damaged body part and interfaces with the nervous system. For example, Luke Skywalker in “The Empire Strikes Back” had a robotic hand installed after Darth Vadar cut it off. And since Luke Skywalker could control his robotic hand by simply thinking about it, his robotic hand no doubt interfaced with the surviving nerves in his arm.
In a continuing mystery to science, neurons in the mammalian brain and spinal cord do not regrow (unless you count a small population of neurons in the memory (hippocampus) and smell (olfactory) parts of the brain). Thus, given current technology, in order to fix brains and spinal cords, sometimes engineers and doctors try to bypass the site of injury through electronic and computer means.
For example, if someone breaks their spinal cord above a certain point, they are confined to a wheelchair. But, the muscles in their legs are still alive, and the brain can still will commands like “I want to move my leg.” The message, however, cannot travel from the brain to the leg muscles because the spinal cord is damaged.
Enter neuroprosthetics! Somehow, if you could “read out” the command signal from the brain, and use it to stimulate muscles or a robotic limb, you’d have a neuroprosthetic! In fact, a research group in Pittsburgh has used this technique to train a monkey implanted with electrodes in his brain to control a robotic arm to feed itself!
We will demonstrate basic principles of neuroprosthetics using two natural cockroach legs.
For this experiment, you need:
- One SpikerBox (us)
- Two RadioShack Amplifier/Speakers (RadioShack Part)
- Two Cockroach Legs (us or other supplier)
- One Y-splitter (RadioShack Part)
- Two “Patch” or "Laptop" Cables (us or RadioShack Part)
- One Stimulation Cable (us)
To begin, put a cockroach on ice water, and then cut off two of its rear legs. Return the cockroach to its house, but consider the cockroach now retired from scientific service. You don’t want to cut off anymore than two legs, and the cockroach can still get around pretty well with only four legs. Place the two cockroach legs on the cork of your SpikerBox, and hook up one leg to the SpikerBox in the standard way as in experiment one. Now:
- Plug the Y-splitter into the SpikerBox.
- Plug the two patch cables into the Y-splitter.
- Plug the two RadioShack Amplifier/Speakers into the other ends of the two patch cables. One Amplifier/Speaker is for simultaneously listening to the spikes while doing your experiment, and the other Amplifier/Speaker is for stimulating the muscles of the second leg (the SpikerBox alone does not generate enough voltage to stimulate the leg; that’s why we have to go through a secondary amplifier).
- Plug the Stimulation Cable into one of the amplifiers.
- Place two needles into the second cockroach leg, and hook up the stimulation cable to these two needles.
- Turn on one of the amplifier/speakers to hear the spikes, and then turn on the second amplifier (the “stimulating” amplifier). The stimulating leg will move briefly due to capacitative discharge when the amplifier is turned on. Slowly turn up the volume on the stimulating amplifier until the leg starts twitching. Then, turn the volume down below this point. You are bringing the leg just “below threshold” when you do this.
- Now, begin brushing the leg that is hooked up to the SpikerBox. What do you see? Do you notice any different effects on the stimulated leg based on different spike rates?
Happy experiments! Let us know what you find!
We thank the high school students of Clarkston Math, Science, and Technology Academy for suggesting we design an experiment demonstrating neuroprosthetics. We’d also love to say we were the first to pull off this preparation, but quite serendipitously and unknown to us, our friends Mohsen Omrani and Ethan Heming at Queens University in Kinston, Ontario first successfully demo’d the preparation a full three hours before we tried it out, on the same day [May 25th, 2011]!
|1.b.||Each neuron communicates with many other neurons to form circuits and share information.|
|1.c.||Proper nervous system function involves coordinated action of neurons in many brain regions.|
|1.d.||The nervous system influences and is influenced by all other body systems (e.g., cardiovascular, endocrine, gastrointestinal and immune systems).|
|1.f.||This complex organ can malfunction in many ways, leading to disorders that have an enormous social and economic impact.|
|2.a.||Sensory stimuli are converted to electrical signals.|
|2.b.||Action potentials are electrical signals carried along neurons.|
|2.d.||Electrical signals in muscles cause contraction and movement.|
|2.f.||Communication between neurons is strengthened or weakened by an individual's activities, such as exercise, stress, and drug use.|
|2.g.||All perceptions, thoughts, and behaviors result from combinations of signals among neurons.|
|3.b.||Sensory circuits (sight, touch, hearing, smell, taste) bring information to the nervous system, whereas motor circuits send information to muscles and glands.|
|3.d.||Complex responses occur when the brain integrates information from many brain circuits to generate a response.|
|3.f.||The brain is organized to recognize sensations, initiate behaviors, and store and access memories that can last a lifetime.|
|4.e.||Peripheral neurons have greater ability to regrow after injury than neurons in the brain and spinal cord.|
|4.g.||Some neurons continue to be generated throughout life and their production is regulated by hormones and experience.|
|7.a.||The nervous system can be studied at many levels, from complex behaviors such as speech or learning, to the interactions among individual molecules.|
|7.b.||Research can ultimately inform us about mind, intelligence, imagination, and consciousness.|
|7.c.||Curiosity leads us to unexpected but surprising discoveries that can benefit humanity.|
|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.|
|8.b.||Research on humans is an essential final step before new treatments are introduced to prevent or cure disorders.|
|8.c.||Neuroscience research has formed the basis for significant progress in treating a large number of disorders.|
|8.d.||Finding cures for disorders of the nervous system is a social imperative.|