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05.28.2015

Virtual-reality games reduce pain. Now to answer why.

Brain scans are focus of research to understand how immersive worlds help patients tolerate painful procedures

By Michael McCarthy  |  HSNewsBeat  |  Updated 1:00 PM, 05.28.2015

Posted in: Research

  • A visual from SnowWorld, the virtual-reality game that reduces the pain that burn patients experience during dressing changes and therapies. Courtesy of Sam Sharar
For more than 15 years, burn patients at Harborview Medical Center have donned a head-mounted display to play a virtual-reality game while undergoing painful dressing changes and other therapies. 

The computer-driven device immerses the patients in an alternate reality, “SnowWorld,” where they can swoop through an icy canyon and pitch snowballs at snowmen, penguins and igloos.

The experience is so engaging that patients report it significantly reduces their pain and makes procedures more tolerable.

Now UW researchers want to better understand why.

“If we can tease out the biological basis of how virtual reality reduces the perception of pain, we should be able to make the treatment more effective,” said Dr. Sam Sharar, a UW professor of anesthesiology and pain medicine.

Sharar and colleagues Hunter Hoffman, David Patterson and Todd Richards have been conducting a series of experiments by using functional magnetic resonance imaging to observe the brains of courageous volunteers as they play the game while submitting to a painful event.

Hoffman, a research scientist in the Human Photonics Lab, and Patterson, a UW professor of psychology, developed the original SnowWorld system in the 1990s. Richards is a professor of radiology and an expert in functional brain imaging. Sharar has a special interest in non-pharmacological methods of pain management. 

To see which areas of the brain are activated during the virtual experience, Hoffman designed a system that can operate within the powerful magnetic field generated by the imaging device. By using non-metallic fiber optics to display the image, and controller devices that contain non-magnetic metals, volunteers can frolic in SnowWorld inside the scanner.

To simulate the discomfort that burn patients might feel while undergoing a wound cleaning or physical therapy, a thermal device is attached to the volunteers’ skin and generates brief episodes of pain.

The pain-generating device does no harm, Sharar said, as it can deliver a customized level of pain that a volunteer characterizes as a six or seven on a 10-point scale, with 10 being “the worst pain” the volunteer has ever experienced. “Six to seven is painful enough that it bothers the volunteer, but it’s not intolerable and has no lasting effects,” he said.

Of particular interest to the researchers is neural activity in five pain-processing areas in the brain: insula, thalamus, anterior cingulate cortex and the two somatosensory cortices. These areas compose the pain matrix and appear to consistently activate whenever pain is experienced, no matter the source.

The researchers wondered whether the virtual realitygame affected the same brain areas that are affected by opiate analgesics. These are pain-killing drugs related to morphine. Virtual reality alone reduces patients’ perception of pain but is not enough to make burn treatments tolerable. So during treatments, patients typically also take an opiate drug such as hydromorphone. The combination of virtual reality with an opiate is more effective than either intervention alone. This additive effect made the UW researchers wonder if both interventions act through the same brain mechanism.

In one rexperiment, the volunteers were sent into the scanner under four conditions: to play SnowWorld with the drug, without the drug, on the drug alone, and with no drug and no virtual reality game.

Regions of the pain matrix showed less activity when the volunteer played VR alone or with the opioid alone, compared to the baseline (no treatment) condition. But activity was even lower with the combination of virtual reality  and opioid. 
VR-pain-brain
(Click to enlarge.) Outlined at right of the matrix are five areas of the brain; across the bottom are different experimental conditions. The brighter the red-orange, the greater the pain.
matrix of brain scans
(Click to enlarge.) Outlined at right of the matrix are five areas of the brain; across the bottom are different experimental conditions. The brighter the red-orange, the greater the pain.
One possible explanation, Sharar said, was that playing SnowWorld caused the brain to produce opioid-like compounds, called endorphins, that bind to the same brain receptors on which opioid drugs act. Endorphins are generated by the brain in response to pain and are thought to be responsible for the feeling of well being brought on by strenuous exercise – the so-called “runner’s high.”

To test this hypothesis, the researchers conducted another experiment: Volunteers who were known to respond well to virutal reality analgesia received experimental pain on two separate days. On their first day they were randomly assigned to receive either a placebo or a large dose of a drug called naloxone while they played the SnowWorld.

Naloxone blocks the opioid receptors in the brain and is used to save people who have taken an overdose of heroin.

“We gave them an enormous dose, about 10 times the dose you would get in the hospital if you came in with a heroin overdose,” Sharar said.

They found that the analgesic effect was essentially the same whether the volunteer had been given the placebo or naloxone. So virtual reality did not act through the brains’s opioid receptors.

This suggests that other brain circuits can be turned on to  dial down the activity in the pain matrix. It is known, for example, that tasks requiring concentration, such as working math problems, can reduce the perception of pain. So it may be that immersive experience of virtual reality games works in a similar way. 
VR-fMRI
Courtesy of Sam Sharar
(Click to enlarge.) A specially designed display allowed volunteers to experience virtual reality while their brain activity was monitored via functional MRI scan.
illustration of a volunteer watching a video game while undergoing an MRI scan
(Click to enlarge.) A specially designed display allowed volunteers to experience virtual reality while their brain activity was monitored via functional MRI scan.
This observation, said Sharar, suggests that virtual reality's effectiveness might be improved by making it more engaging. Indeed, previous studies in their lab showed that consoles with better visual displays, sound and interactivity are more effective at reducing the perception of pain.

The research team is now engaged in a project, funded by the National Institutes of Health, to discern whether pain perception can be further reduced by drugs that heighten the intensity of the virtual reality experience. To this end, the UW team just completed a series of experiments involving combined virutal reality with low-dose ketamine, a drug that at higher dosages is used as a tranquilizer, an analgesic and anti-depressant. At very low doses, though, the drug also can enhance the intensity of sights and sounds, an effect that has made it a popular recreational drug.

“In this experiment, we’re giving the volunteers very low ketamine doses. They really don’t notice any effects: They’re not sedated nor do they feel an anesthesia effect and they don’t notice any heightened awareness,” Sharar said. Nevertheless, preliminary evidence suggests that they do report a more engaging experience and a greater analgesic effect with virtual reality after taking the drug.

Sharar and colleagues are reviewing the results of the ketamine study and soon will complete a similar study with functional magnetic resonance imaging. Preliminary results suggest ketamine can enhance the virtual reality pain-reducing effect, Sharar said.

“If this proves to be the case," he added, "we may be able to improve the effect of virtual reality not by changing the hardware or by changing the software but by changing the user.”

 
Tagged with: pain management, electronic medicine, brain
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