Understanding pain: Can the brain provide all the answers?

January 7, 2014 by Flavia Di Pietro And James H Mcauley, The Conversation
While a flinch, or a grimace may provide us with clues, ultimately we only know that someone’s in pain if they tell us. Credit: The italian voice/Flickr

We now know that there's much more to pain than simply what is happening in the painful body part, and attention has turned to the role of the brain. But not even this mysterious organ can tell us everything we need to know about pain, at least not yet.

You may wonder why the is part of the discussion about at all. After all, we're not talking about a such as Alzheimer's or stroke.

But we think that the brain is actually the best place to look when trying to understand pain; after all, pain is a purely subjective experience.

The problem is that pain cannot be "seen". While a flinch, a limp, or a grimace may provide us with clues, ultimately we only know that someone is in pain if they tell us they are.

And it doesn't necessarily make sense to only consider the part of the body that's sore – sometimes people report pain in a body part that no longer exists, known as .

Just as not all pain arises as a result of an injury to a body part, not all injuries cause pain.

The brain interprets from the body according to the present context; incoming messages are evaluated concurrently with past experiences, memories, thoughts, and even how the painful body part is perceived. The same injury may cause us pain one day, and no pain the next.

Critically, pain is only experienced if the brain concludes, from this complex interplay, that there's potential for harm or danger to the body.

And many researchers around the world are investigating the function of the brain, or its activity, with different neuroimaging tools.

The most common of these tools is a functional magnetic resonance imaging (fMRI) scanner. New technologies like this provide us with exciting opportunities if we use them to answer important questions, using rigorous methods.

Recent advances in statistical methods have led a US research team to find the answer to a very important question – can we see pain in the brain?

These researchers have discovered a neurologic signature of that is highly sensitive. These patterns of brain activity predicted pain with over 90% accuracy (positive predictive value) in the group of people scanned.

But can a brain scan tell the whole pain story?

Pain provides neuroscientists with a remarkable opportunity to investigate how the brain construes a complex experience. CaptPiper/Flickr

Despite this being perhaps the closest we've ever come to "seeing" pain, there are some things about the study we should keep in mind.

The research used a particular type of stimulation – placing hot thermodes on the skin of the forearm – to produce pain in healthy pain-free participants.

One can assume that the study participants knew they were involved in an experiment, that the pain they were experiencing was going to be short-term, and that the experiment could be stopped if needed.

A major issue then is just how generalisable these findings are. Would we see the same neural signature for pain if we were to scan the brain of someone with a 30-year history of low back pain? Would we capture the complex interplay that has led to the construction of pain in that person, at that time?

This leads to question of whether it is, in fact, worth embarking on a quest to find an objective measure for something that is so fundamentally subjective. It may not be valid or useful to search for a biomarker for pain as we would for cancer or heart disease.

And there's another, very significant, issue to consider.

Identifying a brain-based pain signature has been promoted as a step forward in understanding the pain experience of people who cannot communicate their pain. But we should take a very cautious approach to putting this into practice.

It's not uncommon, even though we know so much about the disconnect between tissue injury and pain, for chronic pain sufferers to be accused of feigning pain simply because no pathology can be seen on an X-ray.

We must avoid simply moving these errors of interpretation from scans of the back to scans of the brain, or people suffering pain will continue to be mistrusted.

To this end, the lead author of the US study rightly warned against the use of a neurologic signature for pain as a "lie detector".

The lack of an objective measure for pain is often seen as a barrier to understanding pain. But pain provides neuroscientists with a remarkable opportunity to investigate how the brain construes a complex experience.

By identifying a neural signature, the US study discussed above has made significant progress towards seeing pain in the brain. Research like this moves us forward on the fascinating road towards understanding pain and brain function.

But answers to questions about a complex and subjective experience are likely to come from more than the identification of a neural signature.

Explore further: Women's chronic pain is more complex, more severe

Related Stories

Women's chronic pain is more complex, more severe

October 24, 2013
(Medical Xpress)—New research from the University of Adelaide has found that chronic pain in women is more complex and harder to treat than chronic pain in men.

BMI not linked to pain after exercise rehab for back pain

December 12, 2013
(HealthDay)—For individuals with chronic low back pain (cLBP), body mass index (BMI) is not significantly associated with self-reported pain and disability, according to a study published in the Dec. 1 issue of Spine.

Brain imaging reveals dynamic changes caused by pain medicines

November 19, 2013
A study in the December issue of Anesthesiology suggests a role for brain imaging in the assessment and potential treatment of chronic pain.

First objective measure of pain discovered in brain scan patterns

April 10, 2013
For the first time, scientists have been able to predict how much pain people are feeling by looking at images of their brains, according to a new study led by the University of Colorado Boulder.

Dreading pain can be worse than pain itself

November 21, 2013
Faced with inevitable pain, most people choose to "get it out of the way" as soon as possible, according to research published this week in PLOS Computational Biology. In the study, which was conducted from the Institute ...

Study identifies factors associated with pain one year after breast cancer surgery

December 31, 2013
In a study that included more than 800 women who had undergone surgery for breast cancer, the majority reported some level of pain 12 months after surgery, and factors associated with pain included chronic preoperative pain, ...

Recommended for you

Study uncovers specialized mouse neurons that play a unique role in pain

August 17, 2017
Researchers from the National Institutes of Health have identified a class of sensory neurons (nerve cells that electrically send and receive messages between the body and brain) that can be activated by stimuli as precise ...

Scientists discover powerful potential pain reliever

August 16, 2017
A team of scientists led by chemists Stephen Martin and James Sahn at The University of Texas at Austin have discovered what they say is a powerful pain reliever that acts on a previously unknown pain pathway. The synthetic ...

Scientists use magnetic fields to remotely stimulate brain—and control body movements

August 16, 2017
Scientists have used magnetism to activate tiny groups of cells in the brain, inducing bodily movements that include running, rotating and losing control of the extremities—an achievement that could lead to advances in ...

Scientists give star treatment to lesser-known cells crucial for brain development

August 16, 2017
After decades of relative neglect, star-shaped brain cells called astrocytes are finally getting their due. To gather insight into a critical aspect of brain development, a team of scientists examined the maturation of astrocytes ...

The nerve-guiding 'labels' that may one day help re-establish broken nervous connections

August 16, 2017
Scientists have identified a large group of biological 'labels' that guide nerves to ensure they make the correct connections and control different parts of the body. Although their research was conducted with fruit flies, ...

Navigation and spatial memory—new brain region identified to be involved

August 16, 2017
Navigation in mammals including humans and rodents depends on specialized neural networks that encode the animal's location and trajectory in the environment, serving essentially as a GPS, findings that led to the 2014 Nobel ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.