Successful Generation of a Qualitatively New Memory by Artificial Associating Pre-Stored Information

The team led by the research director Kaoru Inokuchi, professor at University of Toyama has successfully generated an artificial association between stored, non-related contextual and fear information in mice through the synchronous activation of distinct cell ensembles corresponding to the stored information.

Animals have ability to associate distinct units of information to generate a qualitatively new memory. This is one of the strategies that constructs advanced information by relating a lot of information, and an indispensable for survival of animals. In human beings, simultaneous retrieval of distinct units of information that have been stored in the brain sometimes links the original units of information to make an association. The memory association system is extremely important for the formation of knowledge.

Memory is thought to be stored in the brain as an ensemble of cells activated during learning. Although optical stimulation of a cell ensemble triggers the retrieval of the corresponding memory, it is unclear how the association of information occurs at the cell ensemble level. Using optogenetic stimulation without any sensory input in mice, we found that an artificial association between stored, non-related contextual and fear information was generated through the synchronous activation of distinct cell ensembles corresponding to the stored information. This artificial association shared characteristics with physiologically associated memories, such as N-methyl-Daspartate receptor activity- and protein synthesis-dependence. These findings suggest that the association of information is achieved through the synchronous activity of distinct cell ensembles. This mechanism may underlie memory updating by incorporating novel information into pre-existing networks to form qualitatively new memories.