Bad memories may soon be history

Washington: A new animal study has revealed that the place believed to encode positive or negative memories are more flexible than previously thought and they can be overwritten.

In the research, led by Howard Hughes Medical Institute investigator Susumu Tonegawa at the Massachusetts Institute of Technology (MIT), scientists were able to alter the emotional associations of specific memories, by manipulating neural circuits in the brain of mice.

The study revealed that the connections between the part of the brain that stores contextual information about an experience and the part of the brain that stores the emotional memory of that experience are malleable.

The experiments indicated that the cells that store the contextual components of a memory form impermanent or malleable connections to the emotional components of that memory. Tonegawa explained that while a single set of neurons in the hippocampus stores the contextual information about a memory, there are two distinct sets of neurons in the amygdala to which they can connect: one set responsible for positive memory, the other responsible for negative memory.

Circuits connect the hippocampal cells to each of the two populations of cells in the amygdala. There was a competition between these circuits that dictates the overall emotional value and (positive or negative) direction of a memory.

Researchers emphasized that their success in switching the emotion of a memory in mice does not translate to an immediate therapy for patients. There was no existing technology to manipulate neurons in people as they did in their mouse experiments. However, the findings suggested that neural circuits connecting the hippocampus and the amygdala might be targeted for the development of new drugs to treat mental illness.

The report is published in the journal Nature.