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Level 3 Level 3
Invertebrates Invertebrates

Referencing Your Spikes

Ever wondered why we need more than one electrode to measure neural activity? In this experiment, you’ll explore the importance of reference electrodes and learn how their placement affects what we can record.

What Will You Learn?

  • Understand what voltage is and why it’s always relative.
  • Discover the role of reference electrodes in measuring neural signals.
  • Explore how electrode placement influences recordings.

Background

Our nervous system is an intricate network of electrical signals that allow us to sense and respond to the world. But how do we detect these signals? The key lies in understanding voltage, which is the difference in electrical charge between two points. Voltage is what powers your SpikerBox to amplify and record the tiny signals generated by neurons.

You’ve likely seen voltage in action without realizing it—like when your hair floats toward a plastic comb on a dry day. This happens because the comb strips electrons from your hair, creating a difference in charge. Voltage, then, is always relative: it compares one point (the comb) to another (your hair).

This relativity is why we need two electrodes to record neural signals: one to pick up the signal of interest (the “recording” electrode) and one to provide a reference (the “ground” electrode). The difference between these two points is what allows us to “see” the spikes that neurons generate as they communicate.

Procedure

In this experiment, you’ll explore how electrode placement affects what we can detect. By moving the recording and ground electrodes to different locations on a cockroach leg, you’ll observe how the placement influences the clarity and specificity of neural recordings. This hands-on activity will help you understand why reference electrodes are crucial and how scientists carefully configure their setups to isolate signals of interest.

First, Prepare the cockroach leg as seen in the Hear and See a Neuron Experiment.

You will record the neurons from the same leg but with 3 difference pin positions. in the first experiment, please one pin in 2 difference sections of the leg.

Record your dara and make notes of how the neurons sound an how much activity you can see. You may want to blow on the leg or touch the barbs to get a better feel of the signal.

Keep on pin in place, but move the other one so that the 2 pins are close together on the femur. Repeat the experiment above. Do you notice any differences?

Try placing both pins in the coxa and see if this is any different. If you pulled your leg off, you may not have a coxa. In this case you can use the Tibia (the thinner leg just after the knee).

What did you notice? Were you able to see individual spikes better in one area? Was it the location of the pins that mattered? Or was it the distance between the pins?