Neurons
(IN PHOTO)Former mouse embryonic cells are pictured in this undated photograph obtained on January 27, 2010. Researchers have transformed ordinary mouse skin cells directly into neurons, bypassing the need for stem cells or even stemlike cells and greatly speeding up the field of regenerative medicine. REUTERS

An outstanding revelation made by the MIT researchers indicate that memories that have been lost as a result of medical condition such as amnesia can now be recalled by activating the brain cells by exposing them to light. The research paper published in the journal Science explains the technology called optogenetics which has the capability to reactivate memories that were earlier deemed as irretrievable or lost.

Amnesia or loss of memory is a neurological condition that can be caused due to brain damage, injury, disease or psychological trauma. However, its cause has remained a subject for controversy for decades with researchers arguing on the possibilities of its occurrence. With this new development, the researchers have gained insight on amnesia and suggest that the memories do in fact remain, but are simply unable to be recollected.

The study author, the Nobel Prize-winning scientist Susumu Tonegawa of the Massachusetts Institute of Technology, or MIT says, “The majority of researchers have favoured the storage theory, but we have shown in this paper that this majority theory is probably wrong. Amnesia is a problem of retrieval impairment.”

The study was carried out at MIT and the Riken Brain Science Institute in Japan where the researchers stimulated “memory engrams” by using blue light pulses in amnesiac mice. The memory engrams are a population of neurons which get activated in the brain during the process of acquiring memory. Such activated engrams cause physical and chemical changes in the brain and on subsequent reactivation in normal day-to-day life by stimuli such as an image, smell or taste, memories get triggered.

For their study, the researchers used the process called optogenetics where in a protein molecule is added to the neuron via an engineered virus to enable them to be activated by light. By doing so the study authors observed that the engram cells in the hippocampus region showed increased sensitivity to blue light and caused the strengthening of synapses, the structures that allow groups of neurons to send signals to each other.

Tonegawa says, “We were able to demonstrate for the first time that these specific cells, a small group of cells in the hippocampus had undergone this augmentation of synaptic strength. Our conclusion is that in retrograde amnesia, past memories may not be erased, but could simply be lost and inaccessible for recall. These findings provide striking insight into the fleeting nature of memories, and will stimulate future research on the biology of memory and its clinical restoration.”

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