The inner workings of chronic pain

"Pain is complicated," says Jessica Wojick, a doctoral candidate in the School of Arts & Science'sDepartment of Biology. It can feel like a mortal enemy and can also serve as protector.

But what governs pain? What processes do the body and mind undergo when they experience-and cope-with it?

"If you touch a hot stove, it will activate specialized neurons in the peripheral nervous system called nociceptors, and those nociceptors will send a signal to your spinal cord, which will then eventually send a signal to the brain," says Wojick. "Even with something as simple as sitting in one position in your chair for too long, nociceptors can become activated, which unconsciously tells you to shift your body to avoid putting too much pressure on a particular joint. This is how we learn about our environment, like what to avoid, and it also allows us to learn to rest and recover when we do have an injury."

Wojick breaks down the experience of pain into three component stages: sensory, cognitive, and emotional. The sensory component derives from the physiological response-the pinching sting of a bee, for instance-while the cognitive aspect is how the brain reasons through the trauma and how to potentially avoid it in the future. Finally, there is the emotional component: This hurts. How do I deal with it moving forward?

That third stage, the emotional component, is where Wojick's research enters the picture, as she tries to understand how we might allay the suffering of people experiencing chronic pain. Wojick's research centers on a specific region in the brain closely associated with the emotional stage of pain: the amygdala.

This association was famously highlighted in a procedure performed in the mid-20th century on a patient named Henry Molaison-best known as H.M.-who underwent a temporal lobectomy to combat severe seizures. Afterwards, Molaison presented a deficiency in his emotional pain response when heated probes were tested on his skin: He did not describe any as painful, no matter how hot they were.

Wojick is trying to understand what happens in situations like with Molaison, as well as what occurs in the brain in positive or rewarding situations, such as imbibing a sweet drink. "When neurons are active, they fire action potentials, and this involves a change in the electrical potential of the cell," says Wojick. "When this firing occurs, there's a big influx of calcium into the cell. Through the use of a tool that can detect this calcium using fluorescence, we can get a sense for how active the cells are."

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