Placebos and pain control
do not have a clear mechanism. Neuroimaging has shown that the belief in that the
magic pill reduces activity in the various parts of the brain called the “pain
matrix”. What doesn’t appear quite so straightforward is that a couple of other
parts of the brain show increased activity, that is the medial and lateral
prefrontal cortex light up.
This intrigued Koban et al who postulated that decision were
being made that there were errors in the signals that the brain was processing
(1). They decided on a series of experiments with 18 undergrads from Ghent who
were fed a story that their brain activity was being measured to determine the
effects of a regular painkiller on their ability to work an attention task on
the computer.
Some had the placebo and
the control group was told that the pill was a sugar pill and they were the
control. So far, so good, but they were dealing with a so-called painkiller so
pain had to be introduced. This was in the form of a heated pad on their arm.
They had to indicate the intensity of the pain so the “effect” of the
painkiller could be monitored.
Errors in the attention
task showed up as potential changes in the EEG measurements. A negative potential
spike occurred as an error was being made and this was followed by a positive
potential spike a fifth of a second later as the awareness of the error was
being processed.
Although there was no
placebo effect on the negative potential, there was an increase in the positive
potential spike with those making an error who had the placebo, suggesting that
the cognitive circuits were working harder at processing the error in incoming
signal compared to the perception of what it should be – they were doing their best at a
cover-up.
So it seems that placebos
work by both turning down the pain monitoring activity, but in addition increase the error handling to confirm the misrepresentation.
I wonder if our brains
respond in the same manner when we are told that the new austerity measures won’t
really be as painful as we think.
