Memories that are lost due to amnesia can be retrieved by using light, according to a study published in the journal Science.
Massachusetts Institute of Technology (MIT) scientists found that memories which seem to be lost are still stored in the brain and be reactivated by using optogenetics – a combination of techniques from optics and genetics to control and monitor the activities of neurons in living organisms.
Scientists in the field hold two main theories about amnesia. While one group believes that the symptom is linked with the storage of the memories, the other argues that it is the inability to retrieve the memories which causes the problem.
“The majority of researchers have favored the storage theory, but we have shown in this paper that this majority theory is probably wrong,” director of the study Susumu Tonegawa said in a press release from the university.
“Amnesia is a problem of retrieval impairment.”
According to the study, memories are stored in the brain by the connections between nerve cells. The ability to retrieve the memories, however, is linked with the strength of these connections.
Scientist administered mice a compound that blocks protein synthesis immediately after a new memory is formed so that synapses are prevented from strengthening.
One day later researchers couldn’t reactivate the memory even when emotional triggers were used.
But when the scientist reactivated the blocked cells by light, they found that the mice showed all the signs of memory restoration.
The research shows clear disassociation between the storage of the memories and retrieval of them.
“The strengthening… is crucial for the brain’s ability to access or retrieve those specific memories, while the connectivity pathways… [allow] the encoding and storage of the memory information itself,” said Thomas Ryan, one of the leading authors of the study.