**Edit: The Heart & Brain SpikerShield has been replaced by the Heart & Brain SpikerBox!**
The Backyard Brains Heart and Brain SpikerShield is pretty amazing-you can use it to look at both the electrical activity of your heart (across your wrists even!) and the rhythmic electrical activity of your brain. As with all our products however, this wasn’t good enough for us, so we’ve been developing even more experiments for it!
You may have seen our recent experiment looking at the human EOG (ElectroOculoGram). It turns out that the eye forms an electric dipole, where the front is more positively charged and the back more negative. When you move a dipole, such as the eye, it creates an easily observable (at least, with our H&B SpikerShield) electric potential deflection. Based on the direction of deflection (positive or negative) it’s even possible to tell which direction the eye is moving in! It’s easy to set up and requires no additional equipment beyond the H&B Bundle.
How strong of a deflection can you or your students create? Can you tell where someone’s looking just from the potential their eye generates? Grab one today to explore this fascinating intersection of neuroscience and physics.
Over the course of the next 10 weeks, I will be designing and running a neuroethological study on the electrical behavior of the South American weakly electric fish. My goal is to develop a Backyard Brains-esque tool to listen to, record, and manipulate the electrical discharge of the electric fish. I will be posting routine updates on my progress, documenting the successes and failures that I run into along the way.
For some basic background, weakly electric fish are capable of generating electric fields which allow them to navigate the environment and communicate with other electric fish.
Eigenmmania Virescens – Glass Knifefish (Photo by. Nadia Milan)
Weakly electric fish have an electric organ, typically located in their tail. This is what allows them to generate electric signals, also known as Electric Organ Discharge (EOD). These electric signals are in the range of millivolts and are used to communicate with other fish and in electrolocation, a process of navigating the environment by means of detecting objects and sources of external electric fields. What separates weakly electric fish from strongly electric fish is the strength of the EOD – strongly electric fish such as electric eels and rays can use their EODs to stun prey or defend themselves.
Electric Organ Discharge?
When in close contact with another fish emitting a similar frequency, weakly electric fish are effectively “blinded” (Watanabe & Takeda, 1963). In order to cope, the weakly electric fish has developed a jamming avoidance response (JAR) in which the fish will adjust their emitted frequencies to diminish electric field disturbances. For example, if two fish emit signal frequencies of 300 Hz and 304 Hz, the beat frequency will be too low (4 Hz) and cause too much interference between the fish. In this case, the fish with the lower frequency might push its frequency down to 292 Hz while the other pushes its frequency up to 312 Hz, resulting in a more ideal beat frequency of 20 Hz.
I plan to experiment with the JAR to further understand the neural mechanisms of these fish – I plan to stimulate the water to mimic the presence of other fish in the tank as a means to investigate. I would like test out the absolute range for these fish and figure out how to reliably set a fish at a certain frequency. There are many more interesting aspects of the weakly electric fish that I have yet to talk about, so stay tuned for more!
By. Davis Catolico