A new study that experimented on mice claims that lost memories are not really lost, but rather stored in the brain, waiting to be restored. The scientists restored these memories with a technology that uses light called optogenetics.
Researchers at the Massachusetts Institute of Technology (MIT) developed a technique that uses light to activate brain cells that could be storing the lost memories of those with retrograde amnesia.
Retrograde amnesia is a form of amnesia resulting from brain injury or traumatic events. The condition has long baffled psychologists, biologists, and clinicians for over 100 years. Experts settled to believe that the memories affected are stored somewhere in the brain but they cannot be restored. The findings of the MIT researchers challenge this belief after locating where the memories are stored-the engram cells.
"The majority of researchers have favored the storage theory, but we have shown in this paper that this majority theory is probably wrong," Susumu Tonegawa, the Picower Professor in MIT's Department of Biology and director of the RIKEN-MIT Center at the Picower Institute for Learning and Memory, said in a press release. "Amnesia is a problem of retrieval impairment."
The researchers believe that the lost memories stored in the engram cells can be restored or reactivated by triggering a particular sight or smell. In 2012, the group used optogenetics to trigger the recall. They focused on the neuron activity of hippocampus, the part of the brain that consolidates both short-term and long-term memories.
The team observed that after exposing the neurons to the light, the synapses, or chemical reaction between neurons, became stronger, suggesting that the block has been removed. The mice also displayed signs of full memory recall.
"If you test memory recall with natural recall triggers in an anisomycin-treated animal, it will be amnesiac, you cannot induce memory recall," Tonegawa said. "But if you go directly to the putative engram-bearing cells and activate them with light, you can restore the memory."
The findings of the study can be used in the development of treatments for people suffering from retrograde amnesia, Alzheimer's disease and other brain disorders.
The study was published in the May 28 issue of Science.