A process called long-term potentation and the influence of a class of substances called calpains, calcium-dependent proteases. Boudry and his team say that calcium is needed to stimulate the protein in our brains that allows our synapses to undergo memory-related changes that can last. When a connection between neurons is repeatedly or strongly activated, like an association between memories, calpains are activated at that exact location. It seems only when calpain come for a visit that we see the transformation from simple experience to lasting memory.

– Dr. Julia Shaw, The Memory Illusion, p. 60