transformative. “It made all the difference in
the world as far as being able to go places,” she
says, adding that her post-stroke pain had com-
pelled her to spend her days on the couch. “I
have so much more energy. My husband says
I seem so much happier. It really changed my
life completely.”
A subsequent part of the study involving both
healthy subjects and chronic pain patients gave
Machado and his colleagues some insight into
why deep brain stimulation appeared to have
benefited patients like Grubb. The researchers
recorded electrical activity from the brains of
participants as they watched a screen while
they had two devices strapped to their arms.
One device delivered a flash of heat to the skin;
the other delivered a harmless buzz. From the
visual cue that appeared on the screen, the
participants could tell which of the two stimuli
they were about to get or if they were going to
get nothing at all.
The researchers compared the brain activity
of participants as they received heat pulses and
buzzes or nothing. They found that the brains of
chronic pain patients responded similarly when
anticipating a painful stimulus and a harmless
one, whereas the brains of healthy volunteers
showed increased activity in certain regions only
when anticipating the heat. When chronic pain
patients repeated the experiment while receiv-
ing DBS, their brain activity was more similar to
that in healthy participants.
To Machado and his colleagues, these findings
suggest that the brains of chronic pain patients
are conditioned by constant exposure to pain to
react as if every stimulus is potentially painful,
causing the patients to live in distress. The DBS
treatment seems to restore a degree of normalcy,
enabling the brain “to again distinguish pain-
ful from nonpainful, which is what you need in
order to be able to function,” Machado says.
Virtual reality may prove to be another wayA WORLD OF PAIN 65