Cell . . . Memory consolidation and forgetting - the battle between two brain waves in non-rapid eye movement sleep.

As we all know, sleep is very important for the consolidation of memory and the forgetting of experiences.however, how sleep regulates and balances the relationship between memory consolidation and forgetting is still an open question.recently, the Karunesh gangly research group of San Francisco veterans medical center and University of California published a long paper entitled "competing roles of slow oscillations and delta waves in memory consolidation versus forgeting" in cell The separation and competition between so and δ wave in memory consolidation and forgetting.previous studies have shown that during non REM sleep, slow wave oscillations, spindles and their precise temporal interactions play a role in the integration of memory consolidation [2].and in non REM sleep, both slow wave oscillation and δ wave are widespread.classical studies initially divided slow wave oscillation and delta wave into two different neurophysiological phenomena, which were composed of low-frequency waves with different spatiotemporal characteristics [3].and in different species, there are two kinds of waves in non REM sleep. One kind of slow wave has more extensive and larger amplitude, but the other type has smaller amplitude and only exists locally.in this work, the authors divided the slow wave areas in non REM sleep into slow wave oscillation (large amplitude, widespread) and δ wave (small amplitude, local presence).Figure 1 distinguishes slow wave oscillation (so) and δ wave. Firstly, the authors classify slow wave oscillation and δ wave according to waveform.under light stimulation, 60% of neurons responded.the authors have designed a closed-loop real-time system to identify slow wave responses in sleep according to the excitation of opsin response [4].in the learning and memory task test of rats, it has been found that sleep dependent memory activation is related to natural learning process [5].slow wave oscillation is very important for sleep dependent memory consolidation of skill learning in rats.what is the role of delta wave in memory consolidation? The authors found that the disturbance could enhance the effect of sleep dependent memory consolidation.the authors want to further explore the neurophysiological basis of this.therefore, the authors further analyzed the effects of slow wave oscillation and δ wave triggered photoinhibition on the time coupling of sleep spindle wave, slow wave oscillation and δ wave.results in the control case, the nesting of δ wave and spindle wave was 1.3 times higher than that of slow wave oscillation and spindle wave. the change of "nesting" index of slow wave oscillation can explain the changes of memory performance in rats. when the slow wave oscillation is disturbed, the disturbance of δ wave has no effect on the training performance of memory task. Therefore, the author thinks that the absolute value of delta wave nesting may not have any effect on the performance of memory task of rats, but its relative value with slow wave oscillation is more important for memory behavior. the authors found that when the so / δ nesting index is low, the time coupling between slow wave oscillation and spindle wave is lower than that between δ wave and spindle wave; and vice versa. the so / δ nesting index is more accurate than slow wave oscillation nesting index alone in predicting memory performance of rats. interestingly, during the control experiment of sleep process after memory task training, it was found that the intensity of reactivating memory decreased with time. and the intensity of memory activation was significantly higher in the delta wave interference group than in the control group. in general, the change of the intensity of memory activation during sleep after training can also be used to predict the performance of rats in memory tasks. secondly, the authors further unravel the effect of the nesting of slow wave oscillation and spindle wave and the nesting of δ wave and spindle wave on the duration of memory activation. the nesting of slow wave oscillation and spindle wave can preserve the intensity of memory activation, while the nesting of delta wave and spindle wave will weaken the intensity of memory activation. in general, the Ganguly research group found that in the process of memory consolidation and forgetting, slow wave oscillation and δ wave neural activation were different during non REM sleep. the precise nesting of SOS and spindles is particularly important for memory consolidation, which may be achieved by its ability to drive and maintain the ability to reactivate awake time memory. the memory activation regulated by delta wave is always delayed during sleep. After the event is turned off, the ability of memory activation is significantly improved, and the performance in memory tasks is better. in the process of sleep dependent memory processing, slow wave oscillation and delta wave compete with each other to promote memory consolidation, which play a separate and competitive role in memory consolidation and memory weakening respectively. The Journal of neuroscience: the official journal of the society for neuroscience 31, 9124-9134, doi:10.1523/JNEUROSCI.0077-11.2011 (2011).2. Bergmann, T. O. & Born, J. Phase-Amplitude Coupling: A General Mechanism for Memory Processing and Synaptic Plasticity? Neuron 97, 10-13, doi:10.1016/j.neuron.2017.12.023 (2018).3. Steriade, M., McCormick, D. A. & Sejnowski, T. J. Thalamocortical oscillations in the sleeping and aroused brain. Science 262, 679-685, doi:10.1126/science.8235588 (1993).4. Gulati, T., Guo, L., Ramanathan, D. S., Bodepudi, A. & Ganguly, K. Neural reactivations during sleep determine network credit assignment. Nature neuroscience 20, 1277-1284, doi:10.1038/nn.4601 (2017).5. Ramanathan, D. S., Gulati, T. & Ganguly, K. Sleep-Dependent Reactivation of Ensembles in Motor Cortex Promotes Skill Consolidation. PLoS biology 13, e1002263, doi:10.1371/journal.pbio.1002263 (2015).