Mark Dombeck, Ph.D. By Mark Dombeck, Ph.D.
Here is something rather interesting even if not quite exactly fresh off the presses. In August last year, UC Irvine neuroscientists doing brain studies with rats were able to demonstrate a connection between the level of emotionality surrounding a memory and how strongly that memory is stored and remembered.
"In their experiments, the researchers placed a group of rats in a well-lit compartment with access to an adjacent dark compartment. Because rats are nocturnal and prefer dark environments, they tended to enter the dark compartment. Upon doing so, however, they were each given a mild foot-shock — an emotional experience that, by itself, was not strong enough to become a long-lasting memory. Some of the rats then had their amygdala chemically stimulated in order to determine what role it played in forming a memory of the experience."
"When they placed the rats that received both the mild foot-shock and the amygdala stimulation back in the well-lit compartment, the researchers found the rats tended to remain there, demonstrating a memory for the foot shock they had received in the dark compartment. These rats, the researchers found, also showed an increase in the amount of the Arc protein in the hippocampus. On the other hand, rats that received only the mild foot-shock and no amygdala stimulation showed no increase in Arc protein. When placed in the well-lit compartment, they tended to enter the dark compartment, suggesting they didn’t remember the foot shock."
"In a separate experiment, we chemically inactivated the amygdala in rats very soon after they received a strong foot-shock," McIntyre said. "We found the increase in Arc was reduced and these rats showed poor memory for the foot shock despite its high intensity. This also shows that the amygdala is involved in forming a long-term memory."
The study cases light on how it is that traumatic intense situations can get imprinted into the brain in such an intense fashion as to cause PTSD-like symptoms. Scientists have long known that memories are stored using an emotional filing system, but this is the first study I’ve ever come across that suggests what the actual mechanisms behind the scenes are, in this case being the Arc protein. Also of interest is the manner in which the researchers were able to keep memories from becoming traumatic for the rats – by shutting down the Amygdala. This line of thinking might suggest future medical interventions designed to keep people from becoming traumatized when they are going into situations where trauma is likely to happen.
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