BALTIMORE, December 19, 2025 – For decades, the prevailing wisdom in neuroscience held that damaged or destroyed neurons are irreplaceable. But if that’s true, how do people regain function after a brain injury? New research suggests the brain doesn’t necessarily *regrow* neurons, but rather cleverly rewires itself, and this process isn’t equal for everyone.
Brain’s Resilience: Surviving Neurons Step Up After Injury
A new study reveals how the brain compensates for damage by strengthening existing connections, but finds recovery differs between sexes.
- Researchers at Johns Hopkins University discovered that surviving neurons sprout new branches to reconnect after traumatic brain injury.
- This “sprouting” process restores connections between the eye and brain in mice, allowing for functional recovery.
- The study revealed that male mice recovered more effectively than female mice through this mechanism.
- Understanding these sex differences could lead to targeted therapies for brain injury recovery.
A study published in JNeurosci offers new insight into this puzzle. A team led by Athanasios Alexandris at Johns Hopkins University investigated what happens within the visual system of mice following a traumatic brain injury. The visual system, responsible for sight, relies on communication between cells in the eye and neurons in the brain; damage disrupts this vital link.
Surviving Cells Rebuild Eye to Brain Connections
Instead of observing widespread regeneration of new cells, the researchers found that the neurons that *survived* the injury adapted. These resilient cells grew additional branches, effectively expanding their reach and forging connections with more neurons than before. This process, known as sprouting, compensated for the cells lost due to trauma. Over time, the number of connections between the eye and the brain returned to levels comparable to those before the injury.
Crucially, these rebuilt connections weren’t merely structural. Brain activity measurements confirmed that the new pathways were functional, efficiently transmitting signals. This means the visual system was able to operate again, despite the initial damage.
What happens when neurons are damaged? The brain doesn’t simply rebuild what was lost. Instead, surviving neurons adapt and create new connections to restore function.
Sex Differences in Visual System Recovery
The study also uncovered a notable difference between male and female mice. Male mice exhibited robust recovery through the compensatory sprouting process, while female mice experienced slower or incomplete repair. The connections between the eye and brain in females didn’t consistently return to pre-injury levels.
According to the authors, these findings suggest that recovery mechanisms differ based on sex. As Alexandris explains, “We didn’t expect to see sex differences, but this aligns with clinical observations in humans. Women experience more lingering symptoms from concussion or brain injury than men. Understanding the mechanism behind the branch sprouting we observed — and what delays or prevents this mechanism in females — could eventually point toward strategies to promote recovery from traumatic or other forms of neural injury.”
The research team intends to further investigate the reasons behind these sex-based differences in repair. By identifying the biological factors influencing neural recovery, they hope to develop improved treatments for brain injuries, including concussions and other forms of trauma.
