New Evidence on Neurogenesis in Adult Brains

Recent research suggests that the human brain can continue producing new neurons well into adulthood, which could finally resolve a long-standing debate in neuroscience.

This growth of new neurons, known as “neurogenesis,” occurs in the hippocampus, an essential area of the brain associated with learning, memory, and emotions.

“Essentially, our findings settle the ongoing discussion about whether adult human brains can generate new neurons,” said Marta Paterlini, a researcher from the Karolinska Institute in Stockholm.

Experts in the field largely support this study as providing solid evidence for adult neurogenesis.

Though one study alone doesn’t offer absolute proof, Dr. Rajiv Ratan, CEO of the Burke Neurological Institute, emphasized it adds strong support to the idea that stem cells and precursors for new neurons are present and proliferating in adults.

He described it as an exciting moment for clinical neuroscience, furthering understanding in the area.

Utilizing Advanced Technologies

The researchers employed sophisticated techniques, such as single-nucleus RNA sequencing and machine learning, to analyze brain tissue samples from various biobanks. Their findings were published in the journal Science.

For decades, it was known that mice and other nonhuman animals can generate new neurons throughout life. However, obtaining quality brain tissue samples from adults proves to be a significant challenge.

Paterlini noted that human tissue is often collected through surgeries or autopsies, which can affect how the samples are preserved and examined, sometimes obscuring newly formed cells. The innovative techniques employed in this study helped the researchers navigate these issues.

The team analyzed over 400,000 hippocampal cell nuclei from 24 individuals and included samples from people aged 0 to 78, encompassing six children and four teenagers.

By employing advanced imaging methods, the researchers mapped locations of new cells in the tissue. They discovered groups of dividing precursor cells situated next to fully developed neurons, mirroring findings from animal studies.

“We didn’t just observe these cells in younger individuals, but also among teenagers and adults,” Paterlini stated. “These are stem cells capable of self-renewal and generating other types of brain cells.”

With these modern technologies, researchers succeeded in identifying new brain cells at various developmental stages—work that would’ve been nearly impossible just a few years prior, Ratan explained.

Additionally, by marking proliferating cells with fluorescent tags, they created a machine learning algorithm that pinpointed cells likely to develop into neurogenic stem cells based on earlier rodent research. Ratan deemed this a smart approach to addressing the complexities of studying brain cell formation in older age groups.

As expected, child brains produced a higher number of new cells compared to adolescents and adults. Interestingly, nine of the 14 adult brains examined using one technique showed signs of neurogenesis, while all 10 analyzed with another technique exhibited new cells. Paterlini cautioned against drawing conclusions regarding the absence of new cells in certain brains, as it remains unclear.

Looking ahead, the researchers might investigate whether neurogenesis in adults is related to conditions like Alzheimer’s or if it simply reflects overall brain health. Dr. W. Taylor Kimberly, chief of neurocritical care at Massachusetts General Brigham and not involved in the study, remarked on the potential significance of their findings.

Kimberly likened the researchers’ efforts to finding “needles in a haystack.” Understanding and tracking these precursor cells could lead to insights about their role in disease.

He envisions differentiating patients with dementia from “super agers,” who maintain cognitive resilience, to uncover links between neurogenesis and health conditions, possibly paving the way for new treatments.

“Although precise therapeutic strategies are still being explored,” Paterlini remarked, “the discovery that adult brains can generate new neurons alters our perspective on lifelong learning and the potential for recovery from injuries, highlighting the untapped capacity of neural plasticity.”