Metro

MIT research casts new light into how memories are retrieved

Neuroscientists at the Massachusetts Institute of Technology say a neural circuit in the brains of humans and other vertebrates plays a hitherto undiscovered role in memory recall.

Scientists previously believed that recalling a memory involved the same neural circuit that was used to form the memory, the university said.

The research team now claims a different “detour circuit” is used to retrieve memories.

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Dheeraj Roy, a graduate student at MIT and one of the senior authors on the study, said the researchers were surprised that the detour circuit was not connected to the memory formation process at all.

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“We expected the detour circuit to at least contribute to formation,” he told the Globe in a telephone interview Wednesday afternoon.

The process of forming a memory begins in a region of the brain’s hippocampus and moves to another part of the brain, the entorhinal cortex, through a neural circuit, which is a group of connected neurons, or nerve cells. The memory leaves traces known as engrams.

“It’s been thought that the circuits which are involved in forming engrams are the same as the circuits involved” in retrieving memories, said Susumu Tonegawa, an MIT professor and one of the senior authors on the study.

But the new research found that the detour circuits instead are involved.

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Why would there be two separate circuits for memory creation and recall? One explanation, researchers said, is that the detour circuit might allow emotions to be attached to memories.

For example, when you recall a fearful memory, hormones called corticosteroids are released to cause stress.

The discovery of the function of the detour circuit might be helpful in Alzheimer’s research, Roy said.

Now that the research team knows the detour circuit plays a role in a person’s ability to recall memories, they plan to study the way that the circuit functions in the brains of patients with early stages of Alzheimer’s, when patients begin to have memory problems.

Alyssa Meyers can be reached at alyssa.meyers@globe.com. Follow her on Twitter @ameyers_.