Neuroscientists at the Institute of Science and Technology Austria (ISTA) examined mouse brains from birth to adulthood, focusing on the complexity of a key memory circuit in the hippocampus<\/a>.<\/p>\n This region of the brain is involved in spatial memory and in consolidating short-term memories into long-term ones.<\/p>\n The team found that in the youngest mouse brains, this network of CA3 pyramidal neurons<\/a> was very dense, with seemingly random connections. As they get older, however, they become more refined and organized.<\/p>\n “This discovery was quite surprising,” says<\/a> Peter Jonas, neuroscientist at ISTA.<\/p>\n “Intuitively, one might expect that a network grows and becomes denser over time,” Jonas explains<\/a>.<\/p>\n “Here, we see the opposite. It follows what we call a pruning model: It starts out full, and then it becomes streamlined and optimized.”<\/p>\n It’s unclear exactly why the brain develops this way, but the researchers believe that neurons might connect more efficiently if the groundwork is already laid.<\/p>\n In a blank slate scenario, however, distant neurons would first have to find each other before they could communicate. That would take longer for a growing brain<\/a> to learn.<\/p>\n Think of it this way: If you had to navigate from one spot to another, that would be much faster if you already had a dense network of roads, and all you had to do was pick which ones to take to get from A to B.<\/p>\n If, on the other hand, you had to build your own road from scratch to reach your destination, it’s probably going to take a lot longer.<\/p>\n The team measured electrical activity and other cellular processes at three developmental stages in mice: just after birth, at around 7 or 8 days of age; in adolescence, between days 18 and 25; and in adulthood, around 45 to 50 days of age.<\/p>\n This revealed that neurons in this mouse hippocampal circuit start off dense and random but refine themselves into a more structured network over time.<\/p>\n The researchers suggest that this may be because the hippocampus has a tough job of processing and linking information from your eyes, ears, and nose.<\/p>\n “That’s a complex task for neurons,” says<\/a> Jonas.<\/p>\n “An initially exuberant connectivity, followed by selective pruning, might be exactly what enables this integration.”<\/p>\n![\"Our](\"https:\/\/www.newsbeep.com\/ie\/wp-content\/uploads\/2026\/05\/Brain-full-642x310.jpg\")
Left: A young mouse hippocampus is packed with a dense network of neurons. Right: This network is pruned as the mouse matures. (\u00a9 Jake Watson\/ISTA<\/a>)<\/p>\n![\"Subscribe](\"https:\/\/www.newsbeep.com\/ie\/wp-content\/uploads\/2026\/03\/Generic-Health-Promo-Final-642x273.jpg\")
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Neurons filled with biocytin \u2013 a tracer that labels them during recording \u2013 are fixed and stained to allow full reconstruction of their shapes. (\u00a9 Jose Guzman\/Jonas group<\/a>)<\/p>\n