Brain rhythms of sleep influence sleep-associated memory consolidation. The modulation of sleep rhythms, such as the sleep slow oscillation (SO), can be used to investigate neurophysiological mechanisms of memory consolidation and the impact of sleep. Previously, closed-loop acoustic stimulation (CLAS) in humans during the SO Up-state successfully enhanced the slow oscillation rhythm and phase dependent spindle activity, although effects on memory retention have varied. Closely comparative studies in rodents that also monitor hippocampal activity are rare [1, 2]. Yet, a recent iEEG study [3] and our forgoing study [2] underscore that the coupling between cortical SO and hippocampal SPWR in non-rapid eye movement (NREM) sleep is most strongly related to memory consolidation. Based on our previous results using single CLAS we developed a double click CLAS, as used in humans, during NREM sleep following the object place recognition (OPR) task. In a within-subject design, subjects (4-5 month male C57BL/6N mice) received the first of two CLAS stimuli either close to the SO Up-state, SO Up-to-Down state of a 4-h retention period, or during a sham session. Preliminary behavioral results show a tendency toward a higher preference index in the OPR task for the Up-to-Down state stimulation as compared to the Up-state stimulation (p = 0.1, Sign Test, n=10).[1] Moreira et al, Elife, 2021, 10; [2] Aksamaz, et al, Eur J Neurosci, 2023; [3] Geva-Sagiv et al, Nat Neurosci, 2023, 26.Supported by BMBF (01GQ1706), DFG (MA2053/9; MA 2053/11), NIH (1R01NS109553, 1R01MH125557)