This is your brain in a SQUID
I spent most of today (Monday, 2 May 2005) at Mass General Hospital's
Magnetometer Laboratory, participating in an experiment for David Gow.
This experiment uses multiple technologies for brain imaging: in
addition to the fairly standard electroencephalography (EEG) and
functional Magnetic Resonance Imaging (fMRI), they're also using the
fairly new magnetoencephalography (MEG) which is a pretty cool
application of a Superconducting Quantum Interference Device (SQUID),
probably the most sensitive measurement technology in existence today.
Today, the first thing they did was to fit me with an EEG cap, which
has about sixty electrodes distributed evenly over the surface of the
scalp. (Yes, one of the reasons they chose me for this experiment is
that my skull is bare, and therefore very accessible.)
Click on the thumbnails for the full size picture.
Here I am, feeling kinda goofy, with the EEG cap in place, as well as
electrodes on my eyebrow, nose, and cheekbone ... which are used to
detect eye blinks. (The tiny microvolt signals from the EEG
electrodes are completely swamped by the millivolt signals from the
muscles of the eyelid, so they need to be able to tell when I'm
blinking my eyes, so they can throw away that data.) There's also an
electrode on my neck that serves as a ground reference. The glasses
are positional sensors, used to nail down the physical position of
each electrode in the cap, for calibration.
Then they put me in a very special room which is shielded against
magnetic interference ... it's actually three rooms, nested one inside
the other, to give the tremendous amount of shielding that they need
to pick up the extremely tiny magnetic signals emitted by the brain.
The multiple door locking mechanism is very sophisticated, and
impressive. Inside this room, I recline in a sort of chaise lounge,
with my head inside the SQUID magnetometer, and the EEG cap hooked up
so they can gather EEG and MEG data at the same time.
The experimenters watch me on a TV monitor while I'm sealed in the
shielded room. This is a picture of the TV monitor. I'm reclining
with my head in the SQUID (you can just barely see the bottom of it,
the whole thing is the size of a refrigerator) while holding a button
box on my lap. The screen at the lower left is displaying
instructions, while pneumatic headphones are playing speech samples
into my ears, and I push buttons according to what I hear. Meanwhile
the EEG and MEG are recording what parts of my brain are being used to
make the decisions.
The experience of being sealed in this room, while instrumented to the
gills, is sort of similar to being in an isolation tank (ask me about
that sometime). I was focusing so hard on the task that I almost
forgot that there was an outside world. It took about an hour and a
half, and my butt was asleep by the end of it.
When the experiment is done, they take me out of the shielded room,
and start detaching all the electrodes and things. Here I am holding
the various pigtails and connectors, waiting for them to unhook me.
The "shower cap" prevents the electroconductive paste on my scalp from
contaminating the SQUID equipment.
Once the EEG cap is off, these are the dots of electroconductive paste
that it leaves on my head. There are several EEG caps hanging on the
wall behind me, so you can see what they look like when they're not
being worn. The experimenters very graciously washed all this goop
off and scrubbed me down for a clean head afterwards.
Soon, I will be able to see the data that was collected. The MEG data
should be really dramatic, it will take the form of a movie showing
specific parts of my brain "lighting up" as information moves through
it. Then, in another few weeks, I'll go back for the fMRI experiment,
and we'll see much more detailed images of my brain doing what it does
best. Watch this space for further updates.
This page maintained by
Wil Howitt
or wil a t otolith d o t com
Last updated 2 May 2005
