The popular over-the-counter painkiller acetaminophen (Tylenol) may hinder the brain’s error-detection process, according to a new study by researchers at the University of Toronto and the University of British Columbia.
The research is the first to look at how acetaminophen could be inhibiting the brain’s ability to notice and respond to 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 postdoctoral fellow Dan Randles at the University of Toronto.
Current research is beginning to reveal exactly how acetaminophen inhibits pain and to also show that people are less reactive to uncertain situations while taking 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.”
For the study, two groups of 30 participants were given a target-detection task called the “Go or No Go” test. Participants were asked to hit a Go button every time the letter F flashed on a screen but to hold back from pushing 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 particular brain signals known as 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 significant increase in these ERN and Pe waves.
One group was given 1,000 mg of acetaminophen, the equivalent of a normal maximum dose. Another group was given placebo. The study was double-blind, meaning that neither the researcher running the experiment nor the participants knew whether they had been given a placebo or acetaminophen.
The findings show that the acetaminophen participants exhibited smaller levels of Pe when making mistakes compared to participants who had not taken acetaminophen. This suggests 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.
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, but we need to be aware enough to interfere with these automatic processes and take control.
“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.”
One surprising finding was that participants who took acetaminophen appeared to miss more of the Go stimuli than they should have. Randles plans to explore this more fully by expanding on the error-detection portion of the research to test whether acetaminophen may be leading to mind-wandering and distraction.
“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 findings are published in the journal Social Cognitive and Affective Neuroscience.
Source: University of Toronto