Young neurons (pink), responsible for encoding new memories, must compete with mature neurons (green) to survive and integrate into the hippocampal circuit. Photo courtesy of Kathleen McAvoy, Sahay Lab.
HSCI researchers identify new mechanisms by which new neurons sharpen memories
By Hannah L. Robbins, HSCI Communications
When it comes to the billions of neurons in your brain, what you see at birth is what get — except in the hippocampus. Buried deep underneath the folds of the cerebral cortex, neural stem cells in thehippocampus continue to generate new neurons, inciting a struggle between new and old as the new attempts to gain a foothold in the memory-forming center of the brain.
In a study published online today in Neuron, Harvard Stem Cell Institute (HSCI) researchers atMassachusetts General Hospital and the Broad Institute of MIT and Harvard in collaboration with an international team of scientists found they could bias the competition in favor of the newly generated neurons.
“The hippocampus allows us to form new memories of ‘what, when and where’ that help us navigate our lives,” said HSCI Principal Faculty member and the study’s corresponding author, Amar Sahay, PhD, “and neurogenesis—the generation of new neurons from stem cells—is critical for keeping similar memories separate.”
As the human brain matures, the connections between older neurons become stronger, more numerous, and more intertwined, making integration for the newly formed neurons more difficult. Neural stem cells become less productive, leading to a decline in neurogenesis. With fewer new neurons to help sort memories, the aging brain can become less efficient at keeping separate and faithfully retrieving memories.
The research team selectively overexpressed a transcription factor, Klf9, only in older neurons in mice, which eliminated more than one-fifth of their dendritic spines, increased the number of new neurons that integrated into the hippocampus circuitry by two-fold, and activated neural stem cells. READ MORE