New Neurons Form in the Brain Into the Tenth Decade of Life, Even in People With Alzheimer's

A study of people 79 to 99 years old published in Cell Stem Cell observed the formation of new neurons well into old age, even in those with cognitive impairment and Alzheimer's, reports Medical Xpress . "There was active neurogenesis in the hippocampus of older adults well into their 90s," noted University of Illinois at Chicago Professor Orly Lazarov. "The interesting thing is that we also saw some new neurons in the brains of people with Alzheimer's disease and cognitive impairment." Lazarov added that people who scored better on measures of cognitive function had more newly developing neurons in the hippocampus versus subjects who scored lower on these tests. The implication is that lower levels of neurogenesis in the hippocampus are connected to symptoms of cognitive decline and less synaptic plasticity, rather than to brain pathology levels, which for people with Alzheimer's include clumps of neurotoxic proteins. "In brains from people with no cognitive decline who scored well on tests of cognitive function, these people tended to have higher levels of new neural development at the time of their death, regardless of their level of pathology," Lazarov said. "The mix of the effects of pathology and neurogenesis is complex, and we don't understand exactly how the two interconnect. But there is clearly a lot of variation from individual to individual."