Wake Forest UniversityIf you’re one among the millions who wonder how certain memories stay in the brain longer than others, then here’s some food for thought. Researchers at the Wake Forest University School of Medicine seemed to have figured out the puzzle behind long-lasting memories. The novel analysis elucidates how these memories could be forming in the brain.

These new findings experts hope should someday allow scientists to establish enhanced treatments that help in the prevention and treatment of various conditions. These include post-traumatic stress disorder as well.

“Although many things are known about memories that form from repeat experiences, not much is known with regard to how some memories form with just one exposure,” explained Ashok Hegde, Ph.D., an associate professor of neurobiology and anatomy and the lead investigator.

Hegde reveals that scientists are aware of the fact that people have a tendency to clearly remember extremely happy or sad occasions. This is mainly because of the emotions associated with such incidents. When a person experiences extreme emotions, it triggers the release of a chemical in the brain called norepinephrine. Related to adrenaline, this chemical somehow seems to aid memories in lasting for a long time and in some cases even throughout the life.

The lead researcher explains that when a person poses questions like ‘Where were you when the 9/11 attacks happened?’ most people are able to instantly recall their whereabouts when they heard the news. Remembering the moment like it just happened, the researcher shares that a national tragedy seems to arouse emotion. Somehow memories appear to last for a long time when associated with emotions.

To understand this better, Hegde along with colleagues analyzed the working of norepinephrine in female mice. They examined how the chemical aided female mice in remembering the scent of their male partners in spite of exposure to it just once during mating. The neural circuitry in the accessory olfactory bulb was what researchers studied.

The analysis showed that an enzyme identified as Protein Kinase C (PKC) was activated in mice when they released norepinephrine while mating. Specifically the ‘alpha’ isoform of PKC was uncovered in the accessory olfactory bulb. Possessing about a dozen isoforms, the PKC enzyme is known to exist in the brains of mammals, including humans.

“The fact that PKC-alpha is activated through the release of norepinephrine is an important discovery,” Hegde adds. “It explains how strong memories form for specific sensory experiences.”

Researchers ascertain that in female mice information about the partner’s scent is carried by a chemical called glutamate. While the release of norepinephrine conveys the occurrence of mating, earlier findings show that glutamate and norepinephrine together, but not individually result in strong memory formation for the male’s scent.

“No one knew how this happened,” Hegde further mentioned. “Our findings indicate that the PKC-alpha enzyme tells the nerve cells in the brain that these two chemicals have arrived together. PKC-alpha is like the bouncer who lifts the rope blocking the entrance to an exclusive club for strong memories when glutamate and norepinephrine arrive together. If they arrive alone, they can’t get past the velvet rope.”

Researchers explain that the links between nerve cells called synapses are altered when memory is stored in the brain. Strong memories appear to be formed as synapses become stronger through various structural changes taking place at the synapse. Working with glutamate and norepinephrine, PKC-alpha seems to create those changes.

Hegde further remarked that acquiring information on exactly how PKC-alpha can turn genes on in nerve cells could be the next possible step in this line of research. The exact sequence of molecules that are activated by PKC-alpha once understood will allow researchers to block the function of these molecules. They can thus test whether they block memory formation. Future research can supposedly explain the formation of both strong pleasant and unpleasant memories.

The findings are now available online and scheduled to appear in an upcoming issue of Neuroscience.