Researchers at the University of California have successfully managed to erase and reactivate memories in rats, managing to alter their response to past events.
"We can form a memory, erase that memory and we can reactivate it, at will, by applying a stimulus that selectively strengthens or weakens synaptic connections," said senior author Roberto Malinow, MD, PhD, professor in the Department of Neurosciences and neurobiology section of the Division of Biological Sciences.
Scientists modified a group of nerve cells in the brain making them sensitive to light. To associate the sensation of light to pain, they stimulated the genetically modified cells and shocked the rat at the same time. This made the rat associate pain with light.
Analyses revealed chemical changes within the optically stimulated nerve synapses, a sign of synaptic strengthening.
In the next stage of the experiment, researchers demonstrated that they could weaken this circuitry by stimulating the same nerves with a memory-erasing, low-frequency train of optical pulses . The result was that the rats would no longer respond to light with fear which means that the memory has been erased.
What was discovered so far was intriguing but the most startling discovery came when the scientists found that they could re-activate the lost memoy by re-stimulating the same nerves with a memory-forming, high-frequency train of optical pulses, which means that the rats brain is capable of what in computer science terms would be overwritten data recovery, which is nothing short of amazing. The rats once again responded to light with fear without the need for the re-shocking.
"We can cause an animal to have fear and then not have fear and then to have fear again by stimulating the nerves at frequencies that strengthen or weaken the synapses," said Sadegh Nabavi, a postdoctoral researcher in the Malinow lab and the study's lead author.
In terms of potential clinical applications, Roberto Malinow, who holds the Shiley Endowed Chair in Alzheimer's Disease Research,said "Since our work shows we can reverse the processes that weaken synapses, we could potentially counteract some of the beta amyloid's effects in Alzheimer's patients," he said.the brains of people with Alzheimer's disease weakens synaptic connections in much the same way that low-frequency stimulation erased memories in the rats. "Since our work shows we can reverse the processes that weaken synapses, we could potentially counteract some of the beta amyloid's effects in Alzheimer's patients," he said.