The last new neurons were observed in 13 year olds

The human brain may not be as pliant as was believed, a recent study shows. In this study, bound to provoke argument, researchers observe that the latest neurons form in the brain when the subject is about 13 years old and no later. This finding, published in Nature, contradicts earlier experiments, according to which neurons in the hippocampal region of the brain could be formed even late in adulthood.

Hippocampus

The hippocampus is a region which is believed to be the abode of long-term memory and emotional responses. This was also believed to be true in other mammals such as chimpanzees and rodents.

In the study, the researchers took advantage of the fact that specific antibodies could bind to proteins of interest and indicate their locations in tissue. They thereby identified the locations of the neural precursor cells, proliferating cells and immature neurons in samples from 59 human subjects and traced the development from the foetal stage to old age. Up to 14 weeks of gestation, the three cell types migrated from their point of genesis to the region within the hippocampus – the dentate gyrus – where they stayed and developed. The oldest individual they observed with immature neurons was 13 years old.

The researchers observe that a lack of neurogenesis in the hippocampal region has been suggested in the case of some aquatic mammals like dolphins, porpoises and whales. This is interesting because these mammals are known for their intelligence, longevity and complex behaviour, too. They also offer a reason for why humans appear to differ so drastically from other mammals studied.