Pain is a mysterious beast; it can feel very real even when there's no physical reason for it. Recently, scientists in Finland looked at how your brain handles psychologically induced pain.

What the researchers wanted to know: How does the brain light up in response to physical and psychological pain to the left hand?

What they did: The researchers used 14 young adults who scored high on a test that measures how susceptible people are to hypnosis; they also responded to pain suggestion. Before the imaging session, each person was hypnotized. Then they were positioned inside an MRI machine for functional MRI imaging, in which the machine "watches" your brain work. (It detects increased blood flow, which shows what parts of the brain are active.) Then they were subjected to psychological pain, which was induced by telling them the back of their left hand hurt, followed by physical pain, in which the researchers used a laser on the back of the left hand. The subjects had given permission for this before the experiment.

What they found: Both laser-induced pain and suggestion-induced pain lit up circuitry in the cerebrum that react to pain. But during the pain induced by lasers, the parts of those pain circuits that connect to the senses were more active. During the pain induced by suggestion, a part of the brain involved in the emotional aspects of pain was more active.

What the study means to you: Research like this could help explain the mysteries of pain, which can feel real even if there is not a physical stimulus. If these results hold up, this could even suggest a way to distinguish psychological pain from physical pain.

Caveats: The participants were all susceptible to hypnosis; people who are less suggestible might have different results.

Find out more: An explanation of fMRI

Read the article: Raij, T.T., et al. "Brain Correlates of Subjective Reality of Physically and Psychologically Induced Pain." Proceedings of the National Academy of Sciences. Published online Jan. 31, 2005.

Abstract online: www.pnas.org