Recent quotes:

The Neuroscientific Case for Facing Your Fears – The Atlantic – Medium

When someone encounters a new experience — say, a terrifying rabbit — groups of neurons in their brain fire together, the connections between them become stronger, and molecules accumulate at the places where neurons meet. Many scientists believe that these preserved patterns of strengthened connections are the literal stuff of memories — the physical representations of the things we remember. These connected neuron groups are called engrams. When people bring up old memories, the engram neurons fire up again. They also enter a brief period of instability, when the molecules that preserved the connections between them disappear and must be remade. This process, known as reconsolidation, means that humans are partly reconstructing our memories every time they bring them to mind. And it means that the act of recollection creates a window of time in which memories can be updated, and fears can be unlearned.

Neuroscientists identify brain circuit necessary for memory formation: New findings challenge standard model of memory consolidation -- ScienceDaily

The researchers labeled memory cells in three parts of the brain: the hippocampus, the prefrontal cortex, and the basolateral amygdala, which stores memories' emotional associations. Just one day after the fear-conditioning event, the researchers found that memories of the event were being stored in engram cells in both the hippocampus and the prefrontal cortex. However, the engram cells in the prefrontal cortex were "silent" -- they could stimulate freezing behavior when artificially activated by light, but they did not fire during natural memory recall. "Already the prefrontal cortex contained the specific memory information," Kitamura says. "This is contrary to the standard theory of memory consolidation, which says that you gradually transfer the memories. The memory is already there." Over the next two weeks, the silent memory cells in the prefrontal cortex gradually matured, as reflected by changes in their anatomy and physiological activity, until the cells became necessary for the animals to naturally recall the event. By the end of the same period, the hippocampal engram cells became silent and were no longer needed for natural recall. However, traces of the memory remained: Reactivating those cells with light still prompted the animals to freeze. In the basolateral amygdala, once memories were formed, the engram cells remained unchanged throughout the course of the experiment. Those cells, which are necessary to evoke the emotions linked with particular memories, communicate with engram cells in both the hippocampus and the prefrontal cortex.