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"Memories are made by messenger RNA (mRNA) that encode β-actin protein. These proteins are responsible for shaping and structuring cells in the neurons. As events unfold, β-actin protein is responsible for reshaping the neurons and creating a path, retracing the synaptic steps. Memory retention is delicate business, and it is possible for even a single molecule to determine whether or not the memory is stored. Any disruptions in the process can result in a lost memory.

"Because the process is so delicate, it has been incredibly difficult for researchers to see it happen in real time. First, they tagged the mRNA which codes for β-actin protein with green fluorescent protein. Aside from the tag, there was no genetic modification performed on the mouse. By keeping the process as streamlined as possible, the team prevented possibly contaminating the results.

"The researchers then stimulated the hippocampus, which is a small region of the brain that has most of the ability to form and store memories. Following stimulation, the researchers were actually able to witness the synthesis of the β-actin-encoding mRNA in the nucleus of the neuron. The molecules were then tracked out to the dendrites, where communication between neurons takes place."

http://www.einstein.yu.edu – Researchers at Albert Einstein College of Medicine developed a mouse model in which molecules crucial to making memories (beta-actin mRNA) were given fluorescent "tags" so they could be tracked. This clip shows them traveling within a live brain cell in real time. Video Credit: Credit: Hye Yoon Park, Ph.D.