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[Summer’16 Internship] Zombie Snails: Lights, please

After a long and difficult time discovering the buccal ganglia, I recommend using a microscope with at least 6-8 Watt LED bulbs or else you will struggle to find the right area. The buccal ganglia is almost bikini-shaped as shown in the previous log from Ramakrishnan et al. 2014 and is seated directly behind the mouth. Best of luck!

By Nancy Sloan


[Summer’16 Internship] Zombie Snails: A new target

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


[Summer’16 Internship] Arduino, EEG, and Free Will: A big “duh” moment

I had been searching for a readiness potential for weeks, trying to sift through noise two orders of magnitude louder than the signal itself, with little success. This morning Greg, my research mentor, pointed out that since I’m using a bipolar electrode EEG, the op-amp is only magnifying the difference between the two leads over my secondary motor area, which happen to be just a few centimeters apart. The signal between the two electrodes is practically identical, which means I won’t be picking up much of anything. Instead, I want to amplify the difference between a lead over the SMA and another lead on some more neutral part of the head.

To do this, I’m placing one electrode over C3, a second electrode on the base of my occiput, and a reference electrode clipped to my left ear. Instead of buying medical grade EEG ear clips, I soldered two washers to a copper alligator clip.

Currently in MATLAB, I’m applying a 0.25 – 64 Hz bandpass Butterworth filter. This seems to be a good range for recognizing slow cortical potentials. I kept picking up EKG pulse artifacts when I used two grounds (one on my hand for EMG, one on my mastoid for EEG), so I’ve removed the EMG ground, which eliminated EKG as well as most cross-talk between the two channels.

By Patrick Glover