Newswise, April 14, 2016 — It's been known for more
than a century that acetaminophen is an effective painkiller, but according to
a new U of T study it could also be impeding error-detection in the brain.
The research, authored by a team including
postdoctoral fellow Dan Randles and researchers from the University of British
Columbia, is the first neurological study to look at how acetaminophen could be
inhibiting the brain response associated with making errors.
"Past research tells us physical pain and
social rejection share a neural process that we experience as distress, and
both have been traced to same part of the brain," says Randles.
Recent research has begun to show how exactly
acetaminophen inhibits pain, while behavioural studies suggest it may also
inhibit evaluative responses more generally. Randles own past research has
found that people are less reactive to uncertain situations when under the
effect of acetaminophen.
"The core idea of our study is that we don't
fully understand how acetaminophen affects the brain," says Randles.
"While there's been recent behavioural research on the effects of
acetaminophen, we wanted to have a sense of what's happening
neurologically."
To test the idea two groups of 30 were given a
target-detection task called the Go or No Go. Participants were asked to hit a
Go button every time the letter F flashed on a screen but refrain from hitting
the button if an E flashed on the screen.
"The trick is you're supposed to move very
quickly capturing all the GOs, but hold back when you see a No Go," says
Randles.
Each participant was hooked up to an
electroencephalogram (EEG), which measures electrical activity in the brain.
The researchers were looking for a particular wave called Error Related
Negativity (ERN) and Error Related Positivity (Pe). Essentially what happens is
that when people are hooked up to an EEG and make an error in the task there is
a robust increase in ERN and Pe.
One group, which was given 1,000 mg of acetaminophen
- the equivalent of a normal maximum dose - showed a smaller Pe when making
mistakes than those who didn't receive a dose, suggesting that acetaminophen
inhibits our conscious awareness of the error.
"It looks like acetaminophen makes it harder to
recognize an error, which may have implications for cognitive control in daily
life," says Randles.
Cognitive control is an important neurological
function because people are constantly doing cognitive tasks that flow
automatically like reading, walking or talking. These tasks require very little
cognitive control because they are well mapped out neurological processes,
notes Randles.
"Sometimes you need to interrupt your normal
processes or they'll lead to a mistake, like when you're talking to a friend
while crossing the street, you should still be ready to react to an erratic
driver," explains Randles.
"The task we designed is meant to capture that
since most of the stimuli were Go, so you end up getting into a routine of
automatically hitting the Go button. When you see a No Go, that requires
cognitive control because you need to interrupt the process."
The study was double blind, so neither the
researcher running the study nor the participant knew whether they had been
given a placebo or acetaminophen.
An unexpected and surprise finding that Randles
plans to explore more closely is that those who received an acetaminophen dose
appeared to miss more of the Go stimuli than they should have.
He plans on expanding on the error detection aspect
of the research to see whether acetaminophen is possibly causing people to
"mind wander" and become distracted.
"An obvious question is if people aren't
detecting these errors, are they also making errors more often when taking
acetaminophen? This is the first study to address this question, so we need more
work and ideally with tasks more closely related to normal daily
behaviour."
The research is published in the current edition of
the journal Social Cognitive and Affective Neuroscience.
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