|Reducing Pain by Shifting Attention|
|By Melissa Lee Phillips |
Neuroscience for Kids Consultant
September 12, 2002
We have all experienced pain in one form or another. From the pain of paper cuts and headaches to that of arthritis and cancer, pain and its treatment are issues that concern us all. Although drugs to relieve pain are available, many come with unpleasant side effects. Moreover, some pain relievers are addictive. Scientists have investigated a method to reduce pain without the use of drugs. In these experiments, researchers studied how attention can influence pain perception and have found that subjects consistently report less pain when they are being distracted.
Susanna Bantick and her colleagues in the Department of Clinical Neurology at Oxford University used the brain scanning method called functional magnetic resonance imaging (fMRI) to study how attention affects pain. Their goal was to observe the changes in brain activity that accompanied changes in pain perception. In their study, Bantick and her colleagues examined pain perception and brain function under two different conditions:
Condition 2: Subjects' attention was directed away from the pain.
To direct subjects' attention away from pain, the researchers used the counting Stroop task. (The original color word Stroop task was not used because it requires that subjects move their heads while talking; this interrupts the brain scanning process.) During the counting Stroop, subjects saw between one and four words written on a screen. The subjects were asked to push a button indicating how many words they saw on the screen during each of two conditions: a neutral condition and an interference condition.
|Counting Stroop Test|
The words were "cat," "fox," "tiger," or "dog." So, for example, a
subject would see:
The subject would push a button for "three" as quickly as possible because there were three words.
The words were "one," "two," "three," or "four." So, for example, a subject might see:
The subject would need to push a button for "three" for this condition also because there were three words. However, because the subject was reading the word "one," the initial instinct was usually to push the "one" button instead of the "three" button. More attention is required to override this instinct and push the correct answer button. The researchers did a preliminary test that showed that reaction times were indeed slower -- and presumably, more attention was required -- for this interference condition.
A painful heat stimulus (50-53.5oC
[122-128.3oF] for 5 seconds) was applied to the subject's left
hand during each counting Stroop task. At the end of the task, the
participants were asked to rate the painful stimulus on a scale of 1 to
Bantick and her coworkers examined brain activity in several areas during this task. Some of these areas are considered to be part of an attentional network that includes the anterior cingulate cortex (ACC) and the orbitofrontal cortex. The ACC is thought to be important for attention, motivation, error detection, and other "higher" functions. It is also activated by moderate to intense pain. The orbitofrontal cortex is activated during mentally demanding tasks, such as when something interferes with completion of a task. Bantick also studied areas in the "pain matrix." These areas are regions in the brain that can be activated by pain alone and include the thalamus, the insula, the cerebellum, and part of the ACC. The researchers compared the brain responses in these areas when the counting Stroop task was difficult to the brain activity when the task was easy.
As expected, the subjects reported lower pain perception during the interference condition than they did during the neutral condition, even though the heat applied to their hands was the same. Additionally, the researchers found that during the difficult interference condition, activation in the attentional network was increased and activation in the pain matrix was decreased! Not only were subjects reporting less pain, but there was significantly less blood flow to the "pain areas" in their brains. It appears as if something as simple as providing a cognitively difficult task can alter brain activity levels and also reduce the perception of pain.
The authors point out that their findings might be specific to a heat stimulus. Additional studies are needed to determine if these results can be extended to pain resulting from cuts, broken bones, or other trauma. It is also not known how effective attention diversion would be in situations of severe or long-lasting pain. Nevertheless, the identification of brain areas involved in attention and pain is an important step in developing new and safer ways to treat pain.
references and more information, see:|
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