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.
Figure legend: Optical stimulation of cell ensembles in the hippocampal CA1 and basolateral amygdala (BLA) generates new associative memory. Diagram showing the experimental scheme. Top panel. Memories for context B and immediate shock in context A were successfully associated. Mice showed high freezing response in context B in which mice were never received shock. Bottom panel. In contrast, mice showed low freezing when optical stimulation was omitted. The thick blue and grey lines represent the presence (ON Dox) and absence (OFF Dox) of doxycycline, respectively. The blue circle represents light stimulation. The c-fos::tTA mice were used in all groups.
Research Director: Kaoru Inokuchi (Professor, Toyama University)
Prof. Inokuchi leads the CREST project titled as “Memory integration process based on cell assembly and neural circuit model” (Project duration: 1 Oct, 2013 - 31 Mar 2019).
Ohkawa N., Saitoh Y., Suzuki A., Tsujimura S., Murayama E., Kosugi S., Nishizono H., Matsuo M., Takahashi Y., Nagase M., Sugimura Y.K., Watabe A.M., Fusao Kato F., and Inokuchi K. “Artificial Association of Pre-stored Information to Generate a Qualitatively New Memory”. Cell Reports, doi: 10.1016/j.celrep.2015.03.017.
Kaoru Inokuchi, Ph.D.
Professor, Department of Biochemistry, GraduateProfessor, Department of Biochemistry, School of Medicine, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama School of Medicine and Pharmaceutical Sciences, University of Toyama
Life Innovation Group, Department of Innovation Research, JST