Misplaced Neurons Still Perform Essential Sensory Functions: UNIGE Study

Can the brain keep working when its architecture changes? Researchers at the University of Geneva (UNIGE) have discovered that neurons located in the wrong place can still carry out their normal function—challenging long-held assumptions about how the brain is organized. Published in Nature Neuroscience, this study reveals an unexpected ability of the brain to adapt. Neurons are specialized cells responsible for transmitting and processing information through electrical and chemical signals. They form the basic units of the brain and nervous system function. Until now, scientists believed that neurons had to be in the correct location for the brain to function properly. But a recent study by UNIGE researchers shows that neurons positioned incorrectly can not only survive, but also completely take over the role of the normal cerebral cortex. To reach this conclusion, the team studied mice with "heterotopias"—malformations where neurons end up in the wrong location, forming clusters beneath the cortex. This phenomenon also occurs in humans and, in severe cases, can lead to epilepsy and intellectual disabilities. Observing these mice, the researchers made a surprising discovery: These misplaced neurons form circuits almost identical to those of the normal cortex, with similar connections to the rest of the brain and spinal cord. Neurons that step in when needed Even more striking, when scientists temporarily deactivated the normal cortex during a delicate sensory task—distinguishing between two whiskers—the mice continued to perform normally. The misplaced neurons had taken over. Conversely, inhibiting these neurons caused the task to fail completely, proving they had become essential for sensory processing. "It's like moving an entire neighborhood to a different part of a city, and the residents still maintain the same relationships and connections with the rest of the city," explains Sergi Roig-Puiggros, postdoctoral researcher at UNIGE's Department of Basic Neurosciences and first author of the study. Implications for medicine and evolution The findings shed light on evolutionary mechanisms that allow new brain structures to emerge. They also open promising avenues for regenerative medicine: "If neurons can function normally in an abnormal architectural context, then neuronal grafts or brain organoids might not need to perfectly replicate natural brain structure to be effective," notes Denis Jabaudon, professor and head of UNIGE's Department of Basic Neurosciences, who led the study. The next step for the research team is to determine whether this preserved function of misplaced neurons occurs only in heterotopias or also in other neurodevelopmental disorders.