Day 9: Thumb's Up

Yesterday was especially exciting because I was allowed to play around with some of the equipment! The instruments that I used were the ones that measured muscle activity/excitability by measuring the voltages of finger muscles with electrodes (the black thing shown on my palm on the right and another shown on the back of my hand in the image to the left). To find where the muscle is so you can attach the electrode, you tense up the muscle. The muscles that I examined here are the first dorsal interroseus (FDI) and the abductor pollicis brevis (APB). Both of these muscles function to abduct (or move away from the body) the index finger and the thumb, respectively. The picture on the left above shows me abducting my index finger and stopping it with my thumb to emphasize the location of my FDI muscle where my FDI electrode is placed.

After setting up the system and running the program, I let the computer record the motor-evoked potentials (MEP, measured in millivolts) in those two muscles. The monitor displays these values on a graph of MEP vs. time. The top bumpy line measures APB activity and the bottom FDI. Throughout the time period during which I recorded data, I maintained a steady rhythm abducting my fingers, making it seem like the muscles had a steady pulse, as illustrated by the graph.

After abducting and resting and abducting and resting and abducting and resting these muscles for at least 5 minutes, I decided that I should add another finger muscle! So I end up adding my abductor digiti minimi (ADM), the abductor muscle of the pinky. I tape the electrode on there as shown in the picture below. It was around this time that one of my mentors tell me that people test the equipment on themselves before testing on others. I think he was trying to tell me that I'll be able to test on people! Not really. I wish he were though. The entire thing was quite informational for me.

Anyway, so the electrode is now attached to my FDI, APB, and ADM. What's that on your wrist? you might ask. Well that is a "dermatrode." I think it's an electrode that is used as a control for the muscle activity measurements. There might be extraneous movements in other muscles affecting the muscles being measured so this helps remove those anomalies. So here is an image of the graphs (to the right). The first static-y line represents the MEP of the ADM, second APB, third FDI. ON TO THE ABDUCTING (of muscles, not people).

Take note of the background image of the graphs. The monitor shows the graph in real time so the x-axis (time) moves, so the graphs are created from the right side of the monitor. More black you see on the graph = More abduction action.

ABDUCT ALL THE FINGERS

rest

Look at the very right side of the screen

ABDUCT 

rest 

Thumb abduction

Index finger abduction

Pinky abduction

After I was done abducting my fingers, I put everything back. The clean-up was as easy as the set-up. So that's how we collect data from the trials! All the equipment--everything in the picture except the tape--is really expensive, and I'm very grateful that I was given the opportunity to experiment with them.

And now, I continue my search for information of how to use the TMS. A significant majority of the websites that I have found always state how the TMS is a therapeutic tool that is now mainly used to treat major depression. Although they are really interesting, they do not relate to my project nor do they mention how and why the TMS is used to stimulate muscles or to locate areas in the brain or even how/why is it used in experiments. Why is that stimulation necessary to obtain results? These are the questions I'm searching the answers for. Wish me luck on my arduous journey.