Researchers at the Institute of Science and Technology Austria have found that the brain's memory center, the hippocampus, begins life with a dense, seemingly random network of connections rather than a blank slate. This network refines itself through pruning, becoming more organized and efficient over time. The discovery challenges the traditional tabula rasa concept.
A team led by Professor Peter Jonas at the Institute of Science and Technology Austria (ISTA) studied the development of the hippocampal CA3 circuit, crucial for memory storage and retrieval. They examined mouse brains at three stages: shortly after birth (days 7-8), adolescence (days 18-25), and adulthood (days 45-50). Using patch-clamp techniques, advanced imaging, and laser methods, the scientists measured electrical signals and observed neural activity precisely. Their findings, published in Nature Communications, reveal that early CA3 networks are extremely dense and random, then streamline through selective pruning. Peter Jonas described the result as surprising. “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,” he said. The professor suggested this initial exuberant connectivity helps neurons quickly integrate sensory inputs like sights, sounds, and smells into cohesive memories. Starting dense avoids the delays of building connections from scratch, which could hinder efficient memory formation if the brain truly began as a blank slate, or tabula rasa. Instead, it resembles a tabula plena, a full slate that sharpens by trimming excess links. ISTA alumnus Victor Vargas-Barroso conducted the core experiments, with co-authors Jake F. Watson, Andrea Navas-Olive, and Alois Schlögl. The research underscores the balance between genetic wiring and environmental shaping in brain development, offering new insights into how experiences form lasting memories.
