Nerve cells in the spinal cord are known to be critical for processing and responding to touch and pain signals, but deciphering the precise mechanisms of these activities has been a challenge. A new miniaturized microscope allows researchers to see the activation of individual spinal cord neurons in real time in freely moving animals.

Neurobiologist Axel Nimmerjahn, a 2011 Rita Allen Foundation Scholar, and his team at the Salk Institute for Biological Studies developed the technology and reported the results from its first use in laboratory mice on April 28 in Nature Communications. The microscope, which is about the size of a penny, shows how groups of sensory neurons in the spinal cord react to different stimuli, and reveals that the activities of single cells correspond to both the category and intensity of signals.

Along with neurons, the researchers investigated real-time changes in astrocytes, cells in the central nervous system that are mainly known for supporting neurons and other cell types, but are also involved in repairing injuries of the brain and spinal cord. Surprisingly, they observed that in astrocytes, acute sensory inputs prompt changes in calcium concentrations—a key signaling currency in the nervous system.

Nimmerjahn and his team are now adapting the technique to enable concurrent measurements of neural responses to touch and pain in both the brain and the spinal cord. These approaches may yield insights into the mechanisms of pain and itch syndromes, spinal cord injuries and neurodegenerative diseases. “Not only can we now study normal sensory processing, but we can also look at disease contexts like spinal cord injury and how treatments actually affect the cells,” Nimmerjahn said in a news story announcing the findings.