Now that I’ve got the ear clip unipolar EEG set up, I’m finally ready to record. I have my subject wear two headbands: one around the head like a normal sweatband and one under the chin and over C3 like in my previous experiments. I had to do a quick test to get the polarity of the electrodes labeled, but now I’ve got a decent setup working. Positive electrode goes over C3, negative goes on the occiput, and the ground gets clipped to the ear. The subject also wears an anti-static cuff, with the alligator clip attached to the barrel jack of the Heart and Brain shield. Here is some preliminary data:
It’s been a good week! Still plenty of work left to do, since there are some issues with alpha waves, and the RP tends to peak slightly after the action itself. Still, this is some exciting progress. I’m using Audacity to manually crop out epochs that occur during enormous DC spikes that max out the recording software. These huge spikes are obviously not EEG data and probably static discharge or issues with grounding. I’m currently working on writing some MATLAB code to automatically remove these trials consistently.
The next step is to verify these initial results using a lot of additional trials. Also I plan to add two more EEG channels to provide some spatial data about the propagation of the readiness potential.
By Patrick Glover
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.
Upon reading a new paper, I have determined a new location for the electrode (when I get that point in the experiment): the esophageal trunk! Ramakrishnan et al. in 2014 studied the buccal A cluster (BAC) cells that fill up the buccal ganglia, 40 in each. These cells vary in location, size, and the cluster that they’re in but essentially are responsible for telling different muscles to move, like opening the mouth or bringing the radula to the surface. All of these BACs have axonal projections through different nerves branching from the ganglia that we’ve talked about before: the lateral buccal neuron (LBN), the posterior buccal neuron (PBN), the esophageal trunks (ETs), and a few through the cerebro-buccal connective (CBC) that all then connect to different muscles. However, every one of these BAC projections goes through the esophageal trunks and none go through the ventro-buccal nerve. My plan was to attach the electrode to the trunk of the lateral and ventral buccal nerves, which is technically still okay, but only one nerve will be receiving signal. In the picture below from Ramakrishnan’s paper, you can see that there are connections in every neuron except for the VBN with the lightest grey view.
HENCE I will be placing the electrode around one of the esophageal trunks for a *hopefully* stronger signal. Until I get to the point of electrode placement, I am continuing the search for the buccal ganglia.
by Nancy Sloan