A study of brain growth indicates that the area of the brain responsible for memory and learning stops producing nerve cells around the age of 13.
Previously, scientist believed that the hippocampus area continued to produce neurons well into adulthood.
The study involved examining brain samples from 59 adults and children. They found no evidence of young neurons or dividing progenitor of neurons in the brain (hippocampus area) of samples from people older than 18. For the brain sample of children between birth and 13 years old they did find evidence of growth.
There is still some controversy as there are past studies that indicate neurogenesis occurs in adults. The authors of the recent report say that these past studies were based on animals and they projected their finding to be similar in humans. In the recent study, they took their sampling from actual human brains.
Adult neurogenesis was observed in rodents and monkeys but it is not known to occur in cetaceans. Cetaceans include dolphins, porpoises and whales.