Year in review: Gaps in brain nets might store memories

Brain cell nets

A HOLEY HYPOTHESIS  Scientists are giving new attention to the holes in nets (green in the three images above) that envelop nerve cells in the mouse brain.

S. Palida et al

Nets that stretch across nerve cells in the brain may store long-term memories, scientists proposed this year (SN: 11/14/15, p. 8). The new idea attempts to explain a great mystery — why some memories last a lifetime even though the molecules thought to store them are routinely destroyed and recreated.

In studies in mice, Sakina Palida of the University of California, San Diego and colleagues found that some components of tough, durable webs known as perineuronal nets can last up to 180 days. What’s more, these nets of proteins and carbohydrates blanket nerve cells across the brain, not just in select areas. New synapses — communication links between nerve cells — poke holes in the nets, leaving behind a pattern that could hold long-term memories. Mice that had trouble making holes in their nets were worse at remembering a fearful signal weeks later, early experiments showed.

The proposal may help explain why people don’t remember events from their first years of life, Palida says. Early on, nerve cells aren’t yet extensively wrapped in perineuronal nets. 

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