The objective of this study was to modify and improve the original design of the RoboRoach kit provided by Backyard Brains, so as to find the optimal way to shock a cockroach before it habituates, and to make the electronics attached to the roach as lightweight as possible. Modifications included the stimulation of the roach's cerci instead of its antennae, the use of audio clips as a source of irregular electrical signals, and the use of wires instead of the stimulator circuit. The results indicated that the roach was more responsive to the stimulation of the cerci; that the audio clips proved to be a better stimulus; and that the range and lightness of the wires provided the roaches ease in mobility.
This study was performed specifically to explore principles of the microstimulation of neurons, proper stimulation frequencies and circuit design, and basic neurophysiology, and to see how these various disciplines could be interrelated and applied.
The RoboRoach kit assembled by Backyard brains was designed to allow human interference in the commands that cockroaches send themselves through nerves, specifically via the antennae. The original design called for the stimulation of the roach’s antennae through a remote controller. The remote controller would cause + 3 V to output from the circuit and into the the roach’s antennae. This shock would cause the the roach to veer towards the opposite direction, thus allowing directional control.
While recreating the RoboRoach project in accordance to the original design suggested by Backyard Brains, several issues came into light. The cockroach seemed to habituate fairly quickly when its antennae was stimulated, and the bulk of the circuit board seemed to hinder the roach’s mobility. To resolve these complications, our group sought to target a more sensitive portion of the roach’s body, to find a method of stimulating the cockroach that would prevent it from habituating, and to reduce the weight on the roach by making the electronics attached to the roach as lightweight as possible.
The more favorable option was to attempt to stimulate the roach’s cerci. A salient anatomical feature of the cockroach, the cerci are sensory structures located at the rear of the roach’s abdomen, which can sense air movements and enable the cockroach to rapidly detect and flee from potential danger. The sensitivity of the cerci led our group to hypothesize that stimulating the cerci would yield better results than stimulating the antennae.
The cockroaches used in this experimental procedure include the blaberus discoidalis, the blaberus giganteus, and a hybrid of the two. Nearly the same surgical procedure and materials suggested by Backyard Brains were used in this project. The roach was first calmed down with a bath of ice water, and then dried off with a paper towel. Throughout the rest of the surgical procedure, if at times the roach began to gain consciousness, it would be necessary to place the roach into the ice water bath.
To ensure that the electrode box would be securely fastened on the roach’s body, it was necessary to sandpaper the wax covering the roach’s head. Superglue was applied to the bottom of the electrode box and then placed on the head of the roach, with the silver wires facing the top. The wings of the cockroach were then spread apart and secured with wax. The most anterior section of the roach’s abdomen was then pierced with a surgical pin, and the ground wire connected to the electrode box was eased into the piercing and then covered with superglue.
Following the insertion of the ground wire, the remaining wires were to be inserted into either the roach’s antennae or cerci. For the antennae, it was necessary to cut 3/4ths of the antennae and to insert the silver wire as deeply as possible, and to cover the area with super glue. For the cerci, it was necessary to trim a part of the cerci and to likewise insert the silver wire as deeply as possible, and to cover the area with super glue.
With the surgical procedure completed, the cockroach was then placed into a clean, empty container under a lamp. Once the cockroach regained consciousness, the circuit board would be fastened into the electrode box, and the battery would placed into the circuit board. Hot glue was then applied to adhere the circuit board to the roach’s body.
The remote control provided by Backyard Brains was then used to stimulate the roach’s antennae/cerci; if its right antennae/cerci was stimulated, the roach would veer to the left, and vice versa. In later experiments, wires were attached to the electrode box, to replace the bulky circuit board and to allow greater movement of the roach.
To substitute the more regular electrical signals controlled by the remote control, the roach was hooked up with wires that were connected to the amplifier and the computer. Through MATLAB, audio files were converted into electrical signals and then sent straight back to the cockroach. These electrical signals proved to be more irregular, and a better response from the roach occurred.
Note: 1 indicates the best in the category, while 5 indicates the worst. For the habituation column, 1 indicates that the roach habituated the slowest, while 5 indicates that it habituated the fastest.
From the results obtained from this project, it is possible to conclude that stimulating the antennae allows better directional control, and that stimulating the cerci allows better forward control. As said, the antennae was proven to have the best turn response. However, it was also proven to have the worst outcome in terms of forward distance and habituation, as warned by the original makers of the RoboRoach. The most balanced form of modification was the stimulation of one cerci and one antennae. The setup that yielded the best response in terms of forward movement and prevention of habituation was feeding the music directly into the roach.
Even though we provided our cockroaches with the means to stay alive (food and water), most of the test subjects failed to stay alive for a long duration of time. Reasons for these issues most likely stem from the surgery performed on the cockroach. Thus, the next steps in this study would entail the examination of ways to minimize invasive surgery, such that the cockroach does not experience as much trauma.
On the other end of the spectrum, it is necessary to modify the signal that is sent into the RoboRoach. Currently, the issue of habituation arises, where the cockroach “gets used to” the incoming stimulus, after a while. To counter this, we have already tested “random” forms of stimulus (i.e. music), which has given promising results. The next step would be to make the setup slightly more compact.
Cockroach.Microsoft® Student 2008 [DVD]. Redmond, WA: Microsoft Corporation, 2007.