By turning off certain brain cells, researchers were able to make mice sense painful stimuli—but not the associated discomfort. Karen Hopkin reports.
Pain. It’s unpleasant. But what if pain could be rendered less…painful…emotionally speaking? Such uncoupling might not be entirely farfetched. Because researchers have located a set of neurons that seem to encode the feelings of hurt that accompany pain.
“Pain is both a sensory and emotional experience.”
Grégory Scherrer, a pain expert at Stanford University.
“Much of the research so far has focused on the sensory aspect of pain perception. And in particular how cells in our nerves are able to detect the stimuli that we perceive as painful.”
But less is known about why most of us find pain so distressing.
So Scherrer and his colleagues set out to first identify those brain cells that are active when an animal experiences pain. The researchers used a miniature microscope to look at the brains of living mice. That technology was developed by Mark Schnitzer, who does neuroscience and applied physics at Stanford.
“This microscope is small and light enough that it can be worn on the head of an adult mouse as the animal behaves in a natural manner.”
When these microscope-wearing mice were poked with a pin or exposed to mild heat or cold, cells in a subregion of their amygdalas lit up.
“So this indicated that there’s a particular type of cell in a given region of the brain that seemed to specifically encode the percept of pain.”
But are these cells responsible for sensing pain…or interpreting the sensation? To find out, the researchers shut the cells down. And they poked the animals again.
“So when we did that, what we observed is that while animals were still withdrawing from the stimulus, indicating that they could detect it, so the sensation aspect of pain was intact, they didn’t seem to care about the stimulus.”
That is, they didn’t make any effort to avoid the place where they experienced the discomfort…which is how mice usually react to pain. The findings are in the journal Science. [Gregory Corder et al., An amygdalar neural ensemble that encodes the unpleasantness of pain]
A future part of treating pain therefore could be to target these particular neurons. You’d still have the physical part of the pain. But the negative perception of the pain could be diminished. Which means: still pain, but also gain.