Simone Viganò | Does the hippocampus coordinate the sequential reactivation of neocortical regions during memory recall?

Classic theories on memory consolidation and recall propose that the hippocampus stores “traces” or “indices” of neocortical representations evoked during learning, and aid memory recall via index-guided reactivation of these representations (e.g., Teyler & DiScenna 1986). Building on system neuroscience and physiology insights, a recent theory argues that the hippocampus acts as a "sequence generator," storing the indices into cell assemblies that recapitulate the sequential activation of neocortical regions (Buzsaki & Tingley 2018): in other words, it might concatenate and reactivate neocortical information into sequences that preserve the ordinal structure of experienced events. In line with this theory, evidence from animal models, human neuropsychology, and neuroimaging supports the role of the hippocampus in encoding sequential information, but a network description of the rhythmic dialogue between hippocampus and neocortex during memory recall of sequential experiences remains unclear. To address this gap in our understanding of the neural bases of memory functions, we designed an experiment where participants learn sensory-motor sequences mapped to verbal cues. Using fMRI, we will localize cortical modules responsive to the stimuli and the hippocampus, and we will use these regions to extract MEG signal during a subsequent recall task, where participants will think about specific sequences cued by verbal labels. We will explore whether neocortical regions activate sequentially and whether/how this activation is coordinated by the hippocampus, leveraging the spatial resolution of fMRI to inform the analysis of temporally precise MEG signals. In this presentation, we will summarise the details of the rationale and of the experimental design, we will outline the amount of resources we will need from the Institute, and we will collect suggestions and advices to strengthen our paradigm.