MIT researchers identify, label and manipulate the neuronal network encoding a memory.

Memory is one of the enduring mysteries of neuroscience. How does the brain form a memory, store it, and then retrieve it later on? After a century of research, some answers began to emerge. It is now widely believed that memory formation involves the strengthening of connections between a network of nerve cells, and that memory recall occurs when that network is reactivated. There was, however, no direct evidence for this.

Now, researchers at MIT show that the cellular networks that encode memories can not only be identified, but also manipulated. In a spectacular study published online last week in the journal Nature, they report that they have labelled the network of neurons encoding a specific memory, and then reactivated the same network by artificial means to induce memory recall.

Where goest thou, O thought?

The search for the memory trace, or ‘engram,’ began in the 1920s, with the work of a Canadian neurosurgeon named Wilder Penfield, who pioneered a technique for electrically stimulating the surface of the brain. Penfield’s aim was to identify and remove brain tumours, or abnormal tissue that caused severe epileptic seizures, while sparing surrounding tissue that controls essential functions like speech or movement…