Department of Physiology, University of Toronto, Toronto, Canada; Program in Neurosciences and Mental Health, Hospital for Sick Children, University Avenue, Toronto, Canada
Department of Biological Sciences, University of Toronto Scarborough, Toronto, Canada; Department of Cell and Systems Biology, University of Toronto, Toronto, Canada
Matthew M Tran
Department of Biological Sciences, University of Toronto Scarborough, Toronto, Canada; Department of Cell and Systems Biology, University of Toronto, Toronto, Canada
Department of Physiology, University of Toronto, Toronto, Canada; Program in Neurosciences and Mental Health, Hospital for Sick Children, University Avenue, Toronto, Canada; Department of Psychology, University of Toronto, Toronto, Canada; Institute of Medical Sciences, University of Toronto, Toronto, Canada
Department of Cell and Systems Biology, University of Toronto, Toronto, Canada; Department of Psychology, University of Toronto, Toronto, Canada; Institute of Medical Sciences, University of Toronto, Toronto, Canada
Department of Physiology, University of Toronto, Toronto, Canada; Program in Neurosciences and Mental Health, Hospital for Sick Children, University Avenue, Toronto, Canada; Department of Psychology, University of Toronto, Toronto, Canada; Institute of Medical Sciences, University of Toronto, Toronto, Canada
Following learning, increased coupling between spindle oscillations in the medial prefrontal cortex (mPFC) and ripple oscillations in the hippocampus is thought to underlie memory consolidation. However, whether learning-induced increases in ripple-spindle coupling are necessary for successful memory consolidation has not been tested directly. In order to decouple ripple-spindle oscillations, here we chemogenetically inhibited parvalbumin-positive (PV+) interneurons, since their activity is important for regulating the timing of spiking activity during oscillations. We found that contextual fear conditioning increased ripple-spindle coupling in mice. However, inhibition of PV+ cells in either CA1 or mPFC eliminated this learning-induced increase in ripple-spindle coupling without affecting ripple or spindle incidence. Consistent with the hypothesized importance of ripple-spindle coupling in memory consolidation, post-training inhibition of PV+ cells disrupted contextual fear memory consolidation. These results indicate that successful memory consolidation requires coherent hippocampal-neocortical communication mediated by PV+ cells.
