New research from Washington University in St. Louis reveals that neurons in the visual cortex — the part of the brain that processes visual stimuli — change their responses to the same stimulus over time.

Although other studies have documented “representational drift” in neurons in the parts of the brain associated with odor and spatial memory, this result is surprising because neural activity in the primary visual cortex is thought to be relatively stable.

The study published today (August 27, 2021) in Nature Communications was led by Ji Xia, a recent PhD graduate of the laboratory of Ralf Wessel, professor of physics in Arts & Sciences. Xia is now a postdoctoral fellow at Columbia University.

“We know that the brain is a flexible structure because we expect the neural activity in the brain to change over days when we learn, or when we gain experience — even as adults,” Xia said. “What is somewhat unexpected is that even when there is no learning, or no experience changes, neural activity still changes across days in different brain areas.”

Researchers in Wessel’s group explore sensory information processing in the brain. Working with collaborators, they use novel data analysis to address questions of dynamics and computation in neural circuits of the visual cortex of the brain.

Study co-senior author Michael J. Goard, from the Neuroscience Research Institute at the University of California, Santa Barbara, showed mice a single, short movie clip on a loop. (They used a section of the opening from a classic Orson Welles black-and-white film, de rigueur for today’s mouse vision studies.) While a mouse watched the movie, researchers simultaneously recorded activity in several hundred neurons in the primary visual cortex, using two-photon calcium imaging.