Your mind might construct reminiscence not by including connections, however by reducing them away.
The hippocampus is without doubt one of the mind’s most essential areas for reminiscence and navigation. It helps convert short-term experiences into lasting recollections, permitting individuals to be taught from and construct on previous occasions. Researchers led by Magdalena Walz, Professor for Life Sciences, and Peter Jonas on the Institute of Science and Technology Austria (ISTA) examine this space intimately. Their newest work, printed in Nature Communications, investigates how a major neural network in the hippocampus changes after birth.
Blank Slate vs. Full Slate
Imagine writing on a completely empty sheet of paper. Every new piece of information is added to a blank surface. This idea is known as tabula rasa, or the “blank slate.”
Now imagine trying to write on a page that already contains markings. New information must either fit around existing material or replace it. This concept is called tabula plena, or the “full slate.”
The debate behind these ideas centers on a major question about development: Are we largely shaped from birth, or do experiences define who we become over time?
Biology reflects the same discussion through the interaction between genetics, which provide the initial framework, and environmental influences, which shape the final outcome.
Researchers in the Jonas group at ISTA applied this question to the hippocampus, the brain region responsible for memory formation and spatial orientation. They wanted to know how the hippocampal network develops after birth and whether it behaves more like a blank slate or a full slate.
Network of interconnected CA3 pyramidal neurons within the mouse hippocampus. As the animals mature, the configuration shifts—the community turns into sparser however extra structured and refined (blue). Credit: © Jake Watson / ISTA
Dense Neural Networks within the Young Brain
The examine targeted on a core hippocampal circuit made up of interconnected CA3 pyramidal neurons. These neurons are closely concerned in storing and retrieving recollections by way of plasticity, the mind’s skill to adapt by altering the power and construction of neural connections.
ISTA alum Victor Vargas-Barroso examined mouse brains throughout three phases of growth: shortly after beginning (day 7-8), adolescence (day 18-25), and maturity (day 45-50).
To examine these networks, he used the patch clamp approach, which measures tiny electrical alerts in numerous elements of neurons, together with presynaptic terminals and dendrites. The workforce additionally used superior microscopy and laser-based instruments to watch exercise inside cells and activate particular person neural connections with excessive precision.
Network of interconnected CA3 pyramidal neurons within the mouse hippocampus: In younger mice, the CA3 community may be very dense, and the connections seem random (yellow). Credit: © Jake Watson / ISTA
Brain Connections Become More Refined Over Time
The researchers found that the CA3 community begins out extraordinarily dense, with connections showing widespread and considerably random. As the animals matured, nevertheless, the community grew to become much less crowded and extra organized.
“This discovery was quite surprising,” says Jonas. “Intuitively, one might expect that a network grows and becomes denser over time. Here, we see the opposite. It follows what we call a pruning model: it starts out full, and then it becomes streamlined and optimized.”
Instead of regularly including connections, the mind seems to start with an overabundance of hyperlinks after which take away a lot of them as growth progresses.
Why Starting “Full” May Help Memory Formation
Researchers are nonetheless investigating why this course of happens. Jonas believes that an initially broad community might assist neurons talk quickly and effectively throughout early growth, a characteristic that’s particularly essential within the hippocampus.
This area does greater than retailer separate items of sensory data, equivalent to sights, sounds, or smells. It combines them into built-in recollections and experiences.
“That’s a complex task for neurons,” Jonas explains. “An initially exuberant connectivity, followed by selective pruning, might be exactly what enables this integration.”
If the hippocampal community started as a real tabula rasa with no present connections, neurons would first have to find and join with each other. According to the researchers, that will make environment friendly communication far harder.
The findings recommend that the mind might not start as an empty system ready to be crammed. Instead, it might begin with a wealthy community of connections that step by step turns into extra environment friendly by way of selective pruning.
Reference: “Developmental emergence of sparse and structured synaptic connectivity in the hippocampal CA3 memory circuit” by Victor Vargas-Barroso, Jake F. Watson, Andrea Navas-Olive, Alois Schlögl and Peter Jonas, 21 April 2026, Nature Communications.
DOI: 10.1038/s41467-026-71914-x
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