What if our memories physically existed in our brains?

Imagine a scientist analyzing memories under a microscope. The idea that a memory can have a physical existence was put forward in 1904 by Richard Semon, a German researcher. For him, experiences leave traces in the brain, called “engrams”. Subsequent stimulation of the engram, if done by the same signals as when it was formed, can lead to memory retrieval. Moreover, the stronger the connections between the neurons of the engram, the longer the memory will be. However, at the beginning of the 20^and century, no scientific experiment could support it.

Since 2013, the theory of the engram is once again at the center of research. Indeed, new hypotheses suggest, indirectly, the presence of these physical traces of memory. Two neuroscientists analyzed them. Their study is published in the journal Science.

Search for engrams

In each research, the experiment was conducted on mice. In the first, the scientists pointed to memory loss in those who were deprived of a lateral amygdala neural network. To them, this suggests the probable presence of an engram. In the second, the researchers stimulated a set of neurons in the dentate gyrus of the hippocampus, which activates when we experience fear. Indeed, mice experienced fear following this, yet without experiencing it. This suggests the presence of a memory, which has not been reactivated by an external signal. And so, the existence of a potential engram.

Questions remain

The engrams would be composed of neurons. A study published in December 2019 demonstrated that a certain type of set of synapses could be observed in certain configurations, always related to memory and memories. This grouping of synapses would help in the construction of memory. Thus, we can consider the engram as a basic unit of our memory. However, there are still many questions, especially about how it works.