Do long-term memories punch holes in the brain?

How the brain encodes and stores memories is one of the enduring mysteries of neuroscience. Memories are thought to be encoded by the strengthening of synaptic connections, and many researchers believe that they are retained by proteins at the synapses. And yet, while memories can persist over our entire lifetimes, these synaptic proteins are continuously being destroyed and replaced, over a time-frame of hours or days.

Several years ago, neuroscientist Roger Tsien of the University of California, San Diego, proposed that long-term memories are stored in patterns of holes created within a lattice-like structure called the perineuronal net. Sakina Palida, a graduate student in Tsien’s lab, presented evidence for such a ‘punch-card’ mechanism at the annual meeting of the Society for Neuroscience in Chicago earlier this month.

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A bigger role for the little brain?

In the early 19th century, neuroanatomist Franz Joseph Gall believed that the cerebellum, the little attachment to the brain that packs half of the neurons in our head, is the “organ of the instinct of reproduction.” The bigger it is the stronger our libido.

But if you’ve ever lost your balance, or staggered home from a party after a few too many drinks, you’ll know what happens when it isn’t working properly.

The cerebellum (meaning little brain in Latin) has critical roles in controlling and co-ordinating movement. Without a cerebellum, you would have a hard time walking in a straight line or learning to ride a bike – functions that it performs automatically and unthinkingly.

But some researchers now believe that the humble little brain has roles beyond just fine-tuning movement: It may also contribute to higher mental functions such as thought and emotions.

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