Transcranial Magnetic Stimulation
Feb 14, 2007, 11:07a - Technology
During my neuroscience interviews at Berkeley yesterday, they gave us a tour of the fMRI trailer. I got there late and foolishly took my wallet, replete with mag-stripe credit and gift cards, into the MRI room. Of course I read the warning *after* I left the room, so I was worried that my magic-inferred plastic was now impotent. I checked my ATM card at a Wamu afterwards, and it still worked! I guess I must not have gotten close enough to the magnetized morgue-like inner chamber. Of course, my flaky BART card got scrambled but fortunately I was able to get it replaced. Hopefully my credit card and gift cards are fine too.
fMRI (functional magnetic resonance imaging) is an amazing technology that enables researchers and doctors to examine a human brain by monitoring cerebral blood flow. The basic idea is that if a portion of the brain is active, it will require more oxygen and therefore consume more blood. It's currently one of the best techniques for examining human brains without cracking them open. The magnet at Berkeley is 4 Tesla and apparently cost about $4M. They're also planning to install 2 more fMRI machines of 3T and 1.5T, made by Siemens. fMRIs have OK spatial resolution (1 mm cube, what's called a "voxel") but delayed onset, as the neural burst may cause blood to flow to that area seconds later. So you can get a decent sense of what's happening at a higher level, but the lower level of individual neurons is pretty much beyond its current reach..
What's more fascinating, though, is that the folks at Berkeley are planning to couple the brain-reading properties of fMRI with the brain-writing properties of TMS. TMS (transcranial magnetic stimulation) is a hand-held wand that can emit pulses of magnetic waves directly into the brain, no surgery required. After we left the fMRI trailer they took us to the TMS room, and asked for volunteers. I sat down in the chair.
Unfortunately, the TMS takes commands from an ancient Windows 95 laptop, and it blue-screened just when they were going to start the pulse train! They rebooted and got it working, so I sat down again.
I'd heard about TMS several years earlier. It's the only stimulating device (fMRI doesn't actually change brain activity) that I'm aware of that doesn't require cracking the skull open, and I'd heard you could do amazing things with it. Becca told me that they demonstrated it in one of her psych classes and, by stimulating the motor cortex, they were able to cause someone to involuntarily raise their arm.
I was so intrigued that I investigated purchasing one about a year ago. I ordered an operator's manual and a TMS catalog from a website. It turns out they're about the price of a new car ($10K-$20K), and for a moment I thought I could forego the purchase of my next car and get this device instead. You're supposed to have official training, but I thought, hey, how hard could it be.
Then I read that it can induce seizures, so there went that idea.
But now I had my chance. Sitting in the chair, the adminstrator made me clench my left fist a few times, before he went to work stimulating my right motor cortex (the right hemisphere controls the movement of the left half of the body, and vice versa). In hindsight, I guess this was a sort of "priming", getting me to stimulate the motor cortex manually first, perhaps so that it could get "warmed up" and increase its sensitization. He administered a 50 pulse train at a frequency of one pulse per second (1 Hz), gradually moving the wand to try to cause movement in different parts of my arm. The first few pulses didn't do much - it felt as if someone was applying short, painless electric shocks to my scalp. But after a few pulses he hit jackpot. My pinkie started clenching and releasing, then all 5 fingers, then my elbow. It was weird - I looked down at my hand doing all of these brief, convulsive movements and I couldn't stop them. It wasn't violent - the movements were small, maybe a centimeter or 2 in distance moved. But I couldn't stop them.
We often think of consciousness and free will as the executor, the part of our brain that's under our control that tells the rest of the body what to do. One current theory in neuroscience gives free will a much more limited power, one of censorship and veto rather than creating and directing new activity. A nasty thought crosses your mind, but your consciousness suppresses it. Did you create the nasty thought, or did it bubble up to your consciousness from some non-conscious neural activity below? You feel compelled to have another bite of ice cream, but (sometimes) you restrain yourself. No one really has a good sense of what the true mechanism underlying consciousness is, and few even have any ideas where to start, but this theory of free will as vetoer, not composer, seems compelling to me. It's what I see when I look at my own thoughts, my own behavior, and the behavior of others.
My hand convulsions felt like the knee-jerk reflex. But instead of touching a peripheral nerve, we were driving the activity straight from the brain.
After it was over, I couldn't wait to do it again. I signed up for a more in-depth TMS study, though I haven't heard back about that. For the next 30 minutes I kept manually flexing my hand and staring at it, unable to fully believe what had just happened. They told me that we don't really understand how TMS works. The coil they used emitted 2T pulses and could penetrate about 1 cm into the brain. I forget what the spatial resolution was.
A frequency of 1Hz is supposed to be safe, though the long-term effects of TMS aren't known. It's used to treat depression and works for some people. It's also starting to be used to treat migraines before they start, during the "aura" phase. I read in the NY Times a few months ago that it stopped the onset of migraine about 60% of the time.
This technology is amazing. We need to figure out how it works so we can expand its applications and increase its safety.
Read comments (4) - Comment
Kevin Fox
- Feb 14, 2007, 11:39a
Ahh, TMS...
Here's a post I wrote just a stone's throw from the Berkeley fMRI trailer about Prof. Ivry and his demonstrations of the TMS in neuroscience class: http://fury.com/article/1144.php
omar
- Feb 14, 2007, 1:04p
i guess there are many possibilities.. would this work if you were sleeping? induced sleep walking... unconscious assassins... my body doing a workout that i don't want to do..
however, weren't you a bit worried about the possible side effects that are not yet understood? what is the effect of randomly stimulating a very select area of the brain in this manner? i imagine there are no long term studies, yet.. though perhaps migraine sufferers are a good test group.
Kathy Loya
- Feb 23, 2007, 6:38a
I think this has interesting applications, not just for motor stimulation, but possibly for other therapies such as treatment of mood disorders non-invasively, non-chemically, and without need of anesthesia. (ECT is coming back into vogue for treatment of serious depression, but that requires anesthesia and the attendant risks.)
ROBIN ALVAREZ
- Mar 15, 2013, 4:53a
Dear friends:
I have read some information about their studies using TMS and
I think it would be very important to talk with you.
My name is Robin Alvarez and I am writing from the National Polytechnic
Quito-Ecuador.
For about 15 years I have dedicated my research to the bioengineering (I
got a PhD at the Polytechnic of Madrid). Specificly, I have been
researching about the behavior of the EEG and its relationship with Low
Intensity - TMS and I think the developed prototypes could be of interest
for you. I have some publications and three patents. We tested these
prototypes with some types of diseases (migraines,fibromyalgia and bipolar
disorder) with amazing results.
Currently I have the possibility to access to a fellowship from my country
and I am looking for a place for my sabbatical during one year at least.
You can find attached my CV and a very important document with my ideas.
I will be waiting for your answer to see if we can interchange ideas.
Best regards.
Sincerely:
Robin G. Alvarez, Ph.D.
Digital signal processing applied to bioengineering.
Department of Electrical & Electronic Engineering
National Polytechnic University
Quito-Ecuador
Telephone: (+593 - 2) 2507-144 / Ext. 2348
Home: +593 2 2 363- 985
Cel.: (+593 84699704)
e-mail: robin.alvarez@epn.edu.ec, arobin7es@yahoo.es
du.ec, arobin7es@yahoo.es
« A New Drug For Cancer?
-
Self-Education »
|