What is the connection between pain and memory?

pain and memory, working memory
 © Katarzyna Bialasiewicz

Researchers are investigating how everyday pain impacts memory – specifically, how do these daily experiences impact the way we think?

“Studies looking at the relationship between pain and cognition have typically focused on patients with chronic pain or research participants given experimentally-induced pain,” said University of Miami PhD graduate student Steven Anderson.

“Even though pain is a common experience for many people, we know surprisingly little about how the everyday experience of pain impacts cognition.”

Recent research found that childhood air pollution can impact the ability to think, much later on in life. And a different study examined the devastation wrought on cognitive abilities by lifelong trauma, specifically sustained during the holocaust by Jewish patients.

Both suggested that life events shape human behaviour, whether in a subtle way via pollution or a solid, gravity-shifting way, as with those who survived the Holocaust.

But what about the normal pains of a life – the headaches, the backaches, the increments of pain that do not tally up to something in the eyes of a doctor?

Higher pain intensity, worse performing working memory

The study used publicly available brain imaging and self-report data from the Human Connectome Project (HCP). Brain imaging and self-report data from 416 HCP participants were analysed using structural equation modelling (SEM), a statistical technique for modelling complex relationships between multiple variables.

In the 228 participants who reported experiencing some level of pain in the 7 days prior to the study, the authors found that higher pain intensity was directly associated with worse performance a commonly used test of working memory, the n-back task.

What is the n-back test?

In the n-back task, participants are shown a series of letters and asked whether the letter they are seeing appeared some number of screens previously. The more screens back in the sequence participants are asked to recall, the more working memory is required.

Interestingly, researchers further found that certain aspects of emotional distress reported by participants, such as anger, fear, and perceived stress, were not associated with working memory performance at all.

‘Different levels of activity’

“We found that healthy participants with even low levels of reported pain had different levels of activity in the vmPFC during the n-back task compared to healthy participants who didn’t report pain. Surprisingly, this pattern of activity was more similar to patients with chronic pain than healthy patients who are exposed to pain manipulations in a laboratory,” said Joanna Witkin, another graduate PhD student in Psychology.

It was found that higher pain intensity actually indirectly associated with worse working memory performance – due to increased activity in a specific region of the frontal cortex, the the ventromedial prefrontal cortex (vmPFC). The vmPFC is a brain region involved in pain, affective distress, and cognition. Interestingly, the relationship between everyday pain and vmPFC brain activity in this study is similar to prior findings in patients with chronic pain.

Read the full study here.

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