Investigating hippocampal-neocortical interactions around sharp-wave ripples

Coordinated activity in the hippocampal-neocortical network around hippocampal sharp-wave ripples (SWRs) plays an instrumental role in memory processing in the brain. SWRs occur in both sleep and awake states, though under two significantly different behavioural and chemical circumstances. Previous studies have reported different patterns of peri-SWR neocortical modulations between these states; however, their findings have been limited to one or a few discrete regions of the neocortex. To extend previous findings, we conducted wide-field optical imaging of the mouse neocortical voltage and glutamate activity combined with hippocampal electrophysiological recording. We found topographically- and temporally-organized patterns of neocortical glutamate and voltage activity around sleep and awake SWRs, though with pronounced differences. These findings highlight the state-dependency of the hippocampal-neocortical network’s computations and possibly functions. Moreover, they provide a spatiotemporal map of the neocortex around SWRs that could guide future studies on the role of hippocampal-neocortical interactions in memory consolidation.