Hi everyone! I’m Cristian, a junior at Nido de Aguilas High School in Chile. Aside from math and engineering, which are my main interests, I enjoy playing drums and reading nonfiction.
During my internship here at Backyard Brains, I’ve been working on building a musical instrument! It is a modification of our Muscle SpikerShield that measures the electrical signals going through your muscles and transforms them into a note or melody according to how much you flex! I feel proud to join a long tradition of musical instrument makers stretching back 35,000 years.
My musical box has four settings that produce four different outputs. You can change between these settings by pressing the red button on the Muscle SpikerShield. The first setting outputs a frequency that is proportional to how much you flex your arm, so if you really tighten your arm, it’ll output a high frequency, and if you untighten it, it’ll output a low frequency.
I am a very efficient coder. Look at my fundamental code. Rejoice in its beauty.
tone(8, finalReading/1.5, 100);
The second setting outputs notes on a chromatic scale, so you can play different melodies by changing how much you flex your arm.
The third setting plays “Mary had a Little Lamb” on repeat and, just like a real musical box, lets you alter the speed at which the melody plays. If nursery rhymes aren’t really your thing, you can always alter the code and change the melody. This is for all our circuit bending friends out there.
Lastly, the fourth setting lets you play the four notes that make up “Mary had a Little Lamb”, so you can try and create the melody yourself by flexing at different strengths, (which is very hard to do).
Below are two pictures of the setup you will need. Make sure to place jumpers in ground and digital pin 8 and connect them to an audio mini plug, as shown below. The miniplug can be from speakers or headphones. You can use alligator clips.
Additionally, make sure to place 3 electrodes in your muscle of preference ( I used my arm), and connect them to the Muscle SpikerShield with the orange electrode cables.
Backyard Brains is live from inside the classroom of Colegio Alberto Blest Gana in Santiago to present you 5 group projects brought to life by creative and passionate students. and the methodology we used to choose the projects. This high school has been like a second lab for Backyard Brains, where the students beta test our hardware prototypes and invent new classroom exercises. This year was the first year where the classroom made independent group projects, with a class size of about 15 students, ranging from 7th grade to high school seniors.
It can be a challenge to involve students in independent projects when it is their first time, so it is important to let the students conceive their own project ideas from the beginning. The ideas need to come from inspiration, not mandated from above. That’s why, to help out in the creative process, we devised an interview that would work like a conversation, where the student can start to imagine what they would like to build, or what problem they would like to solve. You can use this pdf as a guide
To guide some shy students that weren’t sure what they wanted to build, we suggested projects that the students could modify so that they could begin to feel that the idea we gave them is also their own. We then place the people that had similar ideas and interests into the same group. As a suggestion, if you are working with students with very different ages, it is important to mix it up a little in this area: always have a mix of older students with younger students.
The interview resulted in 5 projects:
The Electrocardiogram of the Clam.
This project was chosen by students that had an interest in animal physiological systems. Most of the students didn’t know before this experiment that a clam has a heart, because when you open it, the clam’s organs just look like a blob. It isn’t easy to notice distinct anatomical parts that look so different from the organs of vertebrates. After finding the heart, a challenge for students (and even for us teachers), we needed to make sure the heart was still moving and contracting. Unlike a vertebrate heart, the beat is not like a regular clock, it can stop a long time and then restart again.
When we saw a heart beat, we placed one red signal electrode in the atrium and the other in the ventricle. The third electrode (ground-black) was placed farther away the clam. These three electrodes were connected to the Backyard Brains Heart and Brain SpikerBox to make the recordings.
And glory of glories, we had success!
However, we don’t know if what the students recorded is in fact an artifact arising from relative movement of the recording electrodes, giving rise to a baseline shift that mimics in some ways the P and QRS features of a typical ECG. Our next step is to manually deform the heart to see if similar features arise. If not, then perhaps we observed a real biologically-generated clam electrocardiogram. You can download our recording here.
In this project, chosen by one gamer and talented student, he used the electricity generated by voluntary muscle contraction to take over the keyboard of a computer.
The appeal of this project is that muscle interfaces work like a charm, a microcontroller is easy to program, and it’s all very low cost. To accomplish this, we decided to control a very easy and accessible video game with the electrical impulses of the muscles, using our Muscle SpikerShield combined with the Arduino Leonardo. The advantage of an Arduino Leonardo is a computer can recognize the Leonardo as a keyboard input. The video game he chose was Google Chrome’s offline dinosaur video game: you can play it fine with only one key on the keyboard (the space bar makes the dinosaur jump…though pressing the down arrow key also makes the dinosaur duck). It’s fun, and you don’t need internet or any specialized gamer hardware to run it. You can download the code here.
The idea of this project was to build a labyrinth to learn about cockroach behavior and food preferences. Could they learn the route to reach a preferred food source faster over time, say, a banana slice instead of a potato slice?
Unfortunately, this project was done in the open air during winter, with a temperature of 40-50 degrees Fahrenheit, a temperature at which cockroaches are not that hungry and not highly active, so using food as an incentive didn’t work. Also, another problem was that the cockroaches were able to climb the walls of the labyrinth. Nevertheless, the students got over these obstacles and had success with one experiment: they placed a lid on half of the labyrinth to make that section dark, and left the other half uncovered, so light could get in. They released the cockroaches, and after one minute, all of the three cockroaches were in the dark side, just like Anakin Skywalker. A small sample size, but convincing evidence of what was suspected all along: cockroaches prefer dark spaces.
The Polygraph Lie Detector.
This project was from a group of students interested in the physiology of lying. At Backyard Brains we love to extract and read physiological signals, and as the traditional polygraph measures skin conductance, respiration, blood pressure, and heart rate, building a DIY polygraph is right in our wheelhouse. To keep it simple in the beginning, together with the students we decided to focus on skin conductance alone, something we have been asked to study before many times.
When someone lies, there is the hypothesis that the persons subtly increases sweating. Since sweat is salty water, and salty water is much more conductive than dry skin, we should be able to measure a decrease in skin resistance across the palms when a person is lying.
The first experiment this group did was very simple. They checked the skin resistance using a multimeter and patch electrodes across our inner palms before and after running on the treadmill The results were the following:
Before running 5 kilometers
After running 5 kilometers (24 minutes)
The results are crystal clear, a body covered in sweat is much less resistant to electrical current than dry skin.
The next step was to find a way to graph skin resistance in real time, and test it using lies instead of jogging. The students made a simple circuit in Arduino where the grey cables go from 5 V input to analog 0 in arduino, buuuutttt, the cable is cut and the person must grab each end of the cut cable with each hand. They then used the sample code “graph” which graphs the voltage value of the analog input, which, of course, will change depending on the resistance of the skin across the student’s hands.
When they tested using lies, there was no significant change in the value of the skin resistance, as the effect is simply too subtle, if it even exists at all, to measure using our equipment. Although the final test wasn’t successful, at least the students tore down the myth that galvanic skin response can detect lies by itself. That’s why complete polygraph machines also measures respiration, blood pressure and heart rate, and the combination of all these elements supposedly makes the polygraph a more reliable tool for detecting lies. If we continue this project in the future, we will look into integrating these other physiological signals in addition to skin conductance.
Muscle Electrophysiology in soccer.
This group of students was interested in how electromyography changes when making different strength kicks in soccer: kicks made for small distances, like close passes, and kicks made for big distances, like aiming for the goal or to a player that’s far away. To do this, the group placed two signal electrodes in the abductor muscle of the quadriceps, and the ground on the knee. The students then placed masking tape in the floor, marking the distance in meters, and the subject kicked the soccer ball to a friend waiting at the various meter marks.
The different distances they used were 5 meters (16.4 feet), 3 meters (32.8 feet), 15 meters (49.2 feet), 20 meters (65.5 feet), 25 meters (82 feet), 30 meters (98.5 feet), and 35 meters (114.8 feet). Below is a sample of the data they recollected:
As you can see quite nicely, the amplitude of the EMG of the quadriceps increases as the soccer ball kicks become more forceful. This was our hypothesis, that as you recruit more and more muscle fibers during a movement, the EMG signal amplitude will increase due to the higher number of action potentials generated and the superposition that results.
This experiment on the physiology of sports was very fun for the students. They also tried baseball pitches, but the rapid “snap-back” movement of the arm would always cause the cables attached to the triceps to come flying off. With basketball, they did not notice a dramatic difference between two point and three point shots. So, as the students were happy to report, for now, soccer is the best for studying the physiology of sports using our equipment! We will keep trying with baseball for all the Detroit Tigers fans out there.
These final projects were worked on once a week, for 1.5 hours, for 2.5 months, and on October 30th, the students presented their results to the community to much success. The sports physiology and the clam EKG experiment will be the first to be transformed into formal Backyard Brains experiments on our webpage, so stay tuned! If you are interested to having the students in your school working on personal group projects, feel free to contact us, and we investigate the world together!
Hi! Juan Ferrada here from the University of Santiago again to give you an update on my project with Backyard Brains.
Main Project – Single unit recording from Snail Neurons
First mission – Isolate the Neurons
As we spoke of a month ago, we are trying to record the individual neurons of the giant pacemaker cells of the parietal ganglia of the common garden snail Helix aspersa. Our first step is to isolate this ganglia so we can visualize the famously large F1 neurons, that can reach up to a crazy big 200 um in diameter. After anesthetizing the snail with magnesium chloride, we began the preparation.
Here we can see the exposed cerebral ganglion and parietal ganglion. They are the highly white structures around the yellowish-white esophagus.
We removed the ganglion, and you can see it is surrounded by connective tissue. Using fine #5 forceps, we slowly picked away the tissue…
until, looking at the sample below a RoachScope at high mag, we see what appear to be a cluster of spheres. These, my friends, are the neurons we are looking for.
Second mission – Get an electrode close to the neurons
Now that we have the neurons in our sights, we have to get an electrode near it, not so easy when the sample is under our microscope. Luckily, we used the Backyard Brains Manipulator to move a glass pipette that we made just by holding a hollow borosilicate glass tube (part number 615000 – 1.0 mm x 0.75 mm) over a lighter and pulling it apart in the flame to make a very fine tip. Using the manipulator holding the electrode, we have just enough clearance to move between the sample and the microscope.
We can easily see the pipette tip on our smartphone looking through the RoachScope lens, and we can manipulate the electrode to come close to our neurons, attempting to insert them into the neurons. You can see a brief video of electrode movement below.
Third mission – Get a recording
We have the neurons, we have the electrode, we have the microscope, we have the manipulator. Now it is time to do the recording. This is my trial by fire, the hardest part of the whole experiment. The plan is to stab the cell with a high resistance glass electrode, then listen and record the spontaneous action potentials. Unfortunately, so far we are only getting noise, but we are slowly improving the amplifier setup, experimenting with electrode styles, reducing 50/60 Hz noise, and chasing the dragon of weak signals. We keep trying to catch it. Stay tuned!
Side-Project – Recording from Sea Anemone Tentacles Since we are dealing with glass microelectrodes and amplifying signal in a noisy watery environment, I have also been working with the Backyard Brains team on a project they have had in mind for a long time – extracellular recordings from the tentacles of sea anemones. The lab has been caring for 9 anemones (taken from the intertidal zone near Algarrobo, Chile, an understudied organism called Anemonia alicemartinae). Over the past four months, the Backyard Brains team has been learning how to maintain a prosperous anemone colony. Since these are Humboldt current creatures, they like their water cold. So we have a trick to keep the aquarium under 20 degrees Celcius by having a fan always blowing air over the water. To further keep the anemones healthy we feed them surf clammeat every day, and clean the tank entirely, replacing and remixing the salt water, every 4-6 weeks.
We were originally using long silver wire (32 gauge) inside our pipette but it turned out to be brittle and the insulation susceptible to breaks and shorts, causing a lot of noise. We switched to flexible 30 gauge copper Minatronics wire that we threaded into a glass pipette, sucked up a tentacle, and recorded….nothing. To try to evoke a response, we touched the anemone trunk with a glass probe, but we did not register any electric activity in the tentacles.
Our next step is to try to insert an electrode near the oral disc, where we have read that more neurons are present.
Any Backyard Brains internship has an outreach component, and I have been helping Backyard Brains teach classes in Colegio Alberto Blest Gana in San Ramón, Santiago. In the past few weeks we have been teaching the students, ranging from 11-17, how to read circuit diagrams and use broadboards. We are building electromyogram amplifiers from scratch. I have learned more about electronics in 1 month than all the combined previous months of my life!
Now we are deep in the experiments, and we will update you at the end of May.