Consolidation of Sequential Planning

Thriving in changing environments requires the capacity to evaluate novel courses of action1. This ability is hypothesized to depend on sequential planning via step-by-step simulations of the future 2-4, using cognitive maps or schemas of task contingencies5,6. However, it is still unclear if, how and where in the brain such flexible planning is enacted. In parallel, it is thought that consolidation transforms memory representations over time to promote adaptive behaviour7. Here, we hypothesize that consolidation strengthens cognitive maps of task contingencies used for simulation during sequential planning. To test this, we developed a novel behavioural task and a new multivariate method for analysis of magnetoencephalography (MEG) data. Using choice and reaction time data we dissociated flexible sequential planning from alternative non-sequential strategies, and identified this behaviour with robust neural markers of step-by-step simulation, localized to the anterior medial temporal lobe. Retesting a week later we showed that consolidation enhanced sequential planning and strengthened markers of sequential simulation in the prefrontal cortex, consistent with systems consolidation theory8-15. By revealing that consolidation improves future simulations for flexible planning we open up a new frontier for the investigation of the functional interactions between memory and decision-making.