While we have enjoyed learning about insect neuroscience during the past few years of our adventure, many teachers have asked us: “Do we have to use bugs?” or “Will this work on humans?” Recording from individual neurons or bundles of nerves requires invasive electrodes, so we are limited to insect preparations for neural activity. But…your muscles also use action potentials (spikes) to change shape and contract! Our engineering team worked last year tweaking our SpikerBox design to be able to pick up human muscle action potentials. It was a tad bit trickier, as recording good signal muscle activity non-invasively through skin electrodes takes some noise cancellation techniques. But…it now works! See video below and judge for yourself. This equipment is available now for your growing laboratory.
Hola SpikerHeads! Come by our vendor booth if you are at the Society for Neuroscience meeting! We will be showing off some new products, notably, our EMG SpikerBox for humans! Have you ever recorded your own muscle action potentials? Now you can, live and direct at SfN. Say hello, relax, and do some experiments with us! We will also have our 3D printer running showing how we build our manipulators, and we have some new projects such as the “Salt Shaker,” an update on our dancing cockroach leg experiment. See you all soon. If you mention the word “impedance,” we will present you with a free electrode! While supplies last.
During experiments on the giant axons of the Longfin Inshore Squid (loligo pealei) at the Marine Biological Laboratory in Woods Hole, MA; we were fascinated by the fast color-changing nature of the squid’s skin. Squids (like many other cephalopods) can quickly control pigmented cells called chromatophores to reflect light. The Longfin Inshore has 3 different chromatophore colors: Brown, Red, and Yellow. Each chromatophore has tiny muscles along the circumference of the cell that can contract to reveal the pigment underneath.
We tested our cockroach leg stimulus protocol on the squid’s chromatophores. We used a suction electrode to attach to the squid’s fin nerve, then connected the electrode to an iPod nano as our stimulator. The results were both interesting and beautiful. The video below is a view through an 8x microscope zoomed in on the dorsal side of the fin.
Update: There are some questions as to what is happening and how this works. An iPod plays music by converting digital music to a small current that it sends to tiny magnets in the earbuds. The magnets are connected to cones that vibrate and produce sound.
Since this is the same electrical current that neurons use to communicate, we cut off the ear buds and instead placed the wire into the fin nerve. When the iPod sends bass frequencies (<100Hz) the axons in the nerves have enough charge to fire an action potential. This will in turn cause the muscles in the chromatophores to contract.
A better explanation as well as a few more demos can be found on our TED talk: http://on.ted.com/Gage.