Recently, Italian and American researchers conducted studies showing that transplanting the gut microbiota of young individuals could restore an aging brain’s capacity to form new connections. However, these studies in mice involve fecal transplants.
Restoring a Fundamental Brain Capability
Around the world, many researchers are working on the possibility of rejuvenating the human brain. Various research avenues are being explored, including partial cellular reprogramming, the awakening of neural stem cells, non-invasive electrical stimulation, and brain immunotherapy.
A study recently conducted by the University of California, Irvine (United States) and the Scuola Normale Superiore di Pisa (Italy) explored another path: fecal transplantation. The results of these studies appeared as a preprint in BioRxiv on June 10, 2026. The biologists’ conclusion is the following: transplanting feces from young mice into aged mice would restore their brain’s ability to form new connections.
“These results identify the gut microbiota as an as-yet-unrecognized regulator of neurodevelopmental plasticity and confirm the existence of microbiota-dependent critical periods in brain development.”, as stated in the study.
What These Studies Are Based On
Understanding the stakes of these investigations requires mentioning amblyopia, a relatively common neurological disorder that occurs when the brain favors one eye over the other. The root cause is a defective connection and communication between the eye and the brain’s visual cortex. In children, the problem is resolved quite easily: over several weeks, the dominant eye is covered to force the brain to generate new neural connections. The fact remains that this is possible because children’s brains still enjoy a high degree of neuroplasticity.
Moreover, science has known for some time that the billions of bacteria living in our intestines are capable of influencing how the brain functions. It is therefore not surprising to observe that the microbiome can play a role in certain neurological disorders or diseases such as anxiety, depression, or Alzheimer’s disease.
Promising Results, but Still Insufficient
As part of their work, the biologists gave antibiotics to a group of mice for about ten days to destroy the beneficial bacteria in their intestines. In parallel, a control group received no treatment. Then, all the mice had one eye covered for three days. According to the results, only the brains of mice with an intact microbiome demonstrated neuroplasticity. In other words, simply destroying the beneficial gut bacteria blocked the brain’s capacity to adapt and generate new neural connections.
Building on these findings, the researchers quickly hypothesized that transplanting the microbiome from a young mouse into an older one could restore the neuroplasticity of its brain. They therefore collected fecal matter from a young mouse—rich in good bacteria—to introduce into the digestive system of an adult mouse, with the aim of recolonizing its intestines with a younger microbiome. A second experiment took place, with a control group and the eye-cover test. The results showed that only the brains of mice that received a transplantation displayed neuroplasticity.
Thus, scientists believe this type of transplantation could render the brains of older individuals more malleable. However, the gap between mice and humans remains substantial, so researchers must continue their work. They will need to precisely identify the bacteria responsible for this effect and also, understand the mechanisms at play.
