Learning and memory are assumed to be supported by mechanisms that involve cholinergic transmission and hippocampal theta. Using G protein–coupled receptor-activation–based acetylcholine sensor (GRAB_ACh3.0) with a fiber-photometric fluorescence readout in mice, we found that cholinergic signaling in the hippocampus increased in parallel with theta/gamma power during walking and REM sleep, while ACh3.0 signal reached a minimum during hippocampal sharp-wave ripples (SPW-R). Unexpectedly, memory performance was impaired in a hippocampus-dependent spontaneous alternation task by selective optogenetic stimulation of medial septal cholinergic neurons when the stimulation was applied in the delay area but not in the central (choice) arm of the maze. Parallel with the decreased performance, optogenetic stimulation decreased the incidence of SPW-Rs. These findings suggest that septo–hippocampal interactions play a task-phase–dependent dual role in the maintenance of memory performance, including not only theta mechanisms but also SPW-Rs. Significance Theta oscillations supported by the medial septum are believed to be a critical mechanism for learning and memory. We report that, in addition to theta oscillations, hippocampal SPW-Rs are important. Enhanced cholinergic activation in the hippocampus during the delay between choices in a spontaneous alternation task abolished SPW-Rs and impaired choice performance in mice. Our findings also demonstrate that the outcome of optogenetic manipulation of a key neurotransmitter, acetylcholine (ACh), depends on the state of the brain at the time of the perturbation.

Increasing evidence has shown that intelligence quotient (IQ) depends not only on the aspect of phenomenology such as the size of brain and sexuality but also on the topology of the brain network. We here try to get a deeper understanding by asking how the running mode of the brain network influences IQ. We introduce a parameter $\alpha$ to represent the trade-off between wiring cost and processing efficiency and figure out the optimal value of $\alpha$ by the approach of network reconstruction. A negative correlation between optimal index $\alpha$ and IQ is revealed. To further find out the mechanism for the functional difference between males and females, we move to the local level of brain regions and study the relationship between regional optimal $\alpha$ and IQ. We find that the Pearson coefficients of males are significantly different from that of females, including both global and regional levels. These findings show that the functional differences between individuals, including the differences between males and females, are closely related to the different running modes of their brain networks.

Explosive synchronization in networked second-order Kuramoto oscillators has been well studied recently and it is revealed that the synchronization process is featured by cluster explosive synchronization. However, little attention has been paid to the influence of noise or perturbation. We here study this problem and discuss the influences of noise and perturbation. For the former, we interestingly find that noise has significant influence on the cluster explosive synchronization of those nodes with smaller degrees, i.e., their synchronization will change from the first-order to second-order transition and the critical points for both the forward and backward synchronization depend on the strength of noise. Especially, when the strength of noise is in an optimal range, a synchronization of the nodes with smaller degrees will be induced in the region of coupling strength where they do not display synchronization in the absence of noise. For the latter, we find that the effect of perturbation is similar to that of noise when its duration $W$ is small. However, the perturbation will induce a change from cluster explosive synchronization to explosive synchronization when $W$ is large. Furthermore, a brief theory is provided to explain the influence of perturbations on the critical points.

F-shaped nanoslits were arranged linearly and circularly to manipulate surface plasmon polaritons (SPPs) using circular polarization illumination. Numerical calculations show that when F-shaped nanoslits are linearly arranged, the electric field distribution follows unidirectional stripe-shaped patterns. Focusing is observed with a circular arrangement of the nanoslits under circular polarization illumination with specific handedness. For the latter geometry, electric fields are greatly enhanced and converge to inside the circle. These results are relevant for the design of nanophotonic devices with applications sensitive to polarization, focusing SPPs, and generating large electric fields.

According to the characteristics of the large transmission ratio of the helicopter main reducer in the future, the research on the characteristic distribution of the planetary gear train of the helicopter main reducer is carried out. Because of the characteristics that the heavy load condition in helicopter main reducer’s running and the changeable running state and complex and harsh climatic conditions and the increasing heat of the flow field in the reducer, by the way, the large transmission ratio increases the uncertainty of the planetary gear train operation analysis at the same time, the probability of causing a failure is greater; Especially the complex and variable structure of the helicopter which has large transmission ratio main reducer makes the analysis difficulty further. For ensuring the safety and enhancing the reliability of the helicopter, this paper make a comparative analysis of the time domain characteristics of the state signals under the multi-operating condition between the normal planetary gear and planetary gears with different degrees of failure, to explore the distribution regularity of the fault characteristics of the helicopter main reducer, so as to realize the research on fault diagnosis of helicopter large transmission ratio planetary gear.