Japanese scientists managed to erase memories from the mouse brain.
When we are preparing for an exam, many people advise not to start it at the last moment and be sure to get enough sleep before the responsible day. In addition to the fact that lack of sleep can affect other processes, its role in the process of transferring information from short-term memory to long-term memory is the most important. This process, which is called consolidation, takes place in the brain through a mechanism of long-term potentialization — reinforcement of signal transmission in chemical synapses (contacts between neurons) that persists for a long time. Exactly how and when memories are formed in the brain depends on the timing and the specific groups of neurons involved in the consolidation.
Researchers at Kyoto University used an optogenetics technique — optical exposure of the brain — to disrupt the protein cofilin, which is essential for optimal synapse function. To do this, adenovirus is injected into the brain, which works as a “courier” to deliver a protein associated with a fluorescent marker. When optical exposure is applied, the proteins release oxygen that deactivates cofilin. This makes it possible to locally target specific parts of the brain at a given point in time during information consolidation.
In the experiment, the mouse hippocampus was irradiated twice: immediately after the animal learned a new task, and then during sleep after learning. The result was a loss of memory of the learned task, similar to the way a flash of light from a neuralyzer that was able to erase memories of alien life forms in the “Men in Black” franchise.
Until now, the exact idea of where and when consolidation occurs has remained poorly understood. Using optogenetics to selectively block long-term potentiation within a certain time period, scientists have been able to discover that different phases of synaptic plasticity play different roles. The first wave occurs locally in the hippocampus. The second wave, which occurs during sleep on the same day, organizes neurons into synchronously activated ensembles. And the third wave occurs already in the anterior cingulate cortex during sleep on the second day, which is necessary for further memory stabilization.