To incorporate spatial memory and nonlocal effect of animal movements, we propose and investigate the spatiotemporal dynamics of the single population model with memory-based diffusion and nonlocal ...reaction. We first study the stability of a positive equilibrium and the steady state bifurcation induced by diffusion and nonlocality. We then investigate the impact of the averaged memory period on stability and bifurcation, and show that the combination of the averaged memory period and the diffusion can lead to the occurrence of Turing-Hopf and double Hopf bifurcations. The paper originally derives the normal form theory for Turing-Hopf bifurcation in the general reaction-diffusion equation with memory-based diffusion and nonlocal reaction. This novel algorithm can be widely used to classify the spatiotemporal dynamics near the Turing-Hopf bifurcation point. Finally, we apply the obtained results to a model proposed by Britton and numerically illustrate the spatiotemporal patterns induced by Hopf, Turing-Hopf and double Hopf bifurcations. Stable spatially homogeneous/nonhomogeneous periodic solutions, homogeneous/nonhomogeneous steady states and the transition from one of these solutions to another are provided in this paper. We additionally acquire the coexistence of two stable spatially nonhomogeneous steady states or two spatially nonhomogeneous periodic solutions near the Turing-Hopf bifurcation point.
•Propose the single population model with memory-based diffusion and nonlocal reaction.•Find the codimension-two Turing-Hopf and double Hopf bifurcation in the scalar reaction-diffusion equation.•Develop the normal form of Turing-Hopf bifurcation in the equation with memory-based diffusion and nonlocal term.•Find the coexistence of two stable spatially inhomogeneous steady states or two spatially inhomogeneous periodic solutions.•Find the transition from one of unstable solutions to another stable one.
The hippocampus is vulnerable to uncontrollable stress and is enriched with oxytocin receptors, but their interactive influences on hippocampal functioning are unknown. This study aimed to determine ...the effects of intranasal oxytocin administration on stress-induced alterations in synaptic plasticity and spatial memory in male rats. While vehicle-administered stressed rats showed impairment in long-term potentiation, enhancement in long-term depression, and weakened spatial memory, these changes were not observed in oxytocin-administered stressed rats. To reveal the potential signaling mechanism mediating these effects, levels of phosphorylated extracellular signal-regulated kinases (pERK) in the hippocampus was examined. Western blotting showed that oxytocin treatment blocked stress-induced alterations of pERK. Additionally, the oxytocin receptor antagonist L-368,899 inhibited the oxytocin's protective effects on hippocampal memory to stress. Thus, intranasal administration of oxytocin reduced stress effects on hippocampal synaptic plasticity and memory in rats via acting on oxytocin receptors and regulating ERK activity. This study suggests that exogenous oxytocin may be a therapeutically effective means to counter the detrimental neurocognitive effects of stress.
•Derive the algorithm of normal form of Hopf bifurcation for memory-based diffusion system.•Investigate the direction and stability of Hopf bifurcations in predator-prey system with memory-based ...diffusion.•Find the stable spatially inhomogeneous periodic solutions with mode-1 and mode-2 spatial patterns.•Find the transition from spatially inhomogeneous mode-2 periodic solution to mode-1 periodic solution.
The memory-based diffusion systems have wide applications in practice. Hopf bifurcations are observed from such systems. To meet the demand for computing the normal forms of the Hopf bifurcations of such systems, we develop an effective new algorithm where the memory delay is treated as the perturbation parameter. To illustrate the effectiveness of the algorithm, we consider a diffusive predator-prey system with memory-based diffusion and Holling type-II functional response. By employing this newly developed procedure, we investigate the direction and stability of the delay-induced mode-1 and mode-2 Hopf bifurcations. Numerical simulations confirm our theoretical findings, that is the existence of stable spatially inhomogeneous periodic solutions with mode-1 and mode-2 spatial patterns, and the transition from the unstable mode-2 spatially inhomogeneous periodic solution to the stable mode-1 spatially inhomogeneous periodic solution.
Global Positioning System (GPS) navigation devices and applications have become ubiquitous over the last decade. However, it is unclear whether using GPS affects our own internal navigation system, ...or spatial memory, which critically relies on the hippocampus. We assessed the lifetime GPS experience of 50 regular drivers as well as various facets of spatial memory, including spatial memory strategy use, cognitive mapping, and landmark encoding using virtual navigation tasks. We first present cross-sectional results that show that people with greater lifetime GPS experience have worse spatial memory during self-guided navigation, i.e. when they are required to navigate without GPS. In a follow-up session, 13 participants were retested three years after initial testing. Although the longitudinal sample was small, we observed an important effect of GPS use over time, whereby greater GPS use since initial testing was associated with a steeper decline in hippocampal-dependent spatial memory. Importantly, we found that those who used GPS more did not do so because they felt they had a poor sense of direction, suggesting that extensive GPS use led to a decline in spatial memory rather than the other way around. These findings are significant in the context of society's increasing reliance on GPS.
Living cells actively migrate in their environment to perform key biological functions-from unicellular organisms looking for food to single cells such as fibroblasts, leukocytes or cancer cells that ...can shape, patrol or invade tissues. Cell migration results from complex intracellular processes that enable cell self-propulsion, and has been shown to also integrate various chemical or physical extracellular signals. While it is established that cells can modify their environment by depositing biochemical signals or mechanically remodelling the extracellular matrix, the impact of such self-induced environmental perturbations on cell trajectories at various scales remains unexplored. Here, we show that cells can retrieve their path: by confining motile cells on 1D and 2D micropatterned surfaces, we demonstrate that they leave long-lived physicochemical footprints along their way, which determine their future path. On this basis, we argue that cell trajectories belong to the general class of self-interacting random walks, and show that self-interactions can rule large scale exploration by inducing long-lived ageing, subdiffusion and anomalous first-passage statistics. Altogether, our joint experimental and theoretical approach points to a generic coupling between motile cells and their environment, which endows cells with a spatial memory of their path and can dramatically change their space exploration.
Light exerts profound effects on cognitive functions across species, including humans. However, the neuronal mechanisms underlying the effects of light on cognitive functions are poorly understood. ...In this study, we show that long-term exposure to bright-light treatment promotes spatial memory through a di-synaptic visual circuit related to the nucleus reuniens (Re). Specifically, a subset of SMI-32-expressing ON-type retinal ganglion cells (RGCs) innervate CaMKIIα neurons in the thalamic ventral lateral geniculate nucleus and intergeniculate leaflet (vLGN/IGL), which in turn activate CaMKIIα neurons in the Re. Specific activation of vLGN/IGL-projecting RGCs, activation of Re-projecting vLGN/IGL neurons, or activation of postsynaptic Re neurons is sufficient to promote spatial memory. Furthermore, we demonstrate that the spatial-memory-promoting effects of light treatment are dependent on the activation of vLGN/IGL-projecting RGCs, Re-projecting vLGN/IGL neurons, and Re neurons. Our results reveal a dedicated subcortical visual circuit that mediates the spatial-memory-promoting effects of light treatment.
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•Activation of Re-projecting vLGN/IGL neurons activates neuronal activity in the Re•SMI-32+ ON-type RGCs directly innervate the vLGN/IGL-Re pathway•Activation of the retina-vLGN/IGL-Re pathway promotes spatial memory•Light treatment promotes spatial memory via the retina-vLGN/IGL-Re pathway
Huang et al. identified a visual circuit related to the Re that regulates spatial memory. They demonstrate that the retina-vLGN/IGL-Re pathway mediates the spatial-memory-promoting effects of light treatment.
Selenium is an essential trace element that is delivered to the brain by the selenium transport protein selenoprotein P (SEPP1), primarily by binding to its receptor low-density lipoprotein ...receptor-related protein 8 (LRP8), also known as apolipoprotein E receptor 2 (ApoER2), at the blood-brain barrier. Selenium transport is required for several important brain functions, with transgenic deletion of either Sepp1 or Lrp8 resulting in severe neurological dysfunction and death in mice fed a selenium-deficient diet. Previous studies have reported that although feeding a standard chow diet can prevent these severe deficits, some motor coordination and cognitive dysfunction remain. Importantly, no single study has directly compared the motor and cognitive performance of the Sepp1 and Lrp8 knockout (KO) lines. Here, we report the results of a comprehensive parallel analysis of the motor and spatial learning and memory function of Sepp1 and Lrp8 knockout mice fed a standard mouse chow diet. Our results revealed that Sepp1 knockout mice raised on a selenium-replete diet displayed motor and cognitive function that was indistinguishable from their wild-type littermates. In contrast, we found that although Lrp8-knockout mice fed a selenium-replete diet had normal motor function, their spatial learning and memory showed subtle deficits. We also found that the deficit in baseline adult hippocampal neurogenesis exhibited by Lrp8-deficit mice could not be rescued by dietary selenium supplementation. Taken together, these findings further highlight the importance of selenium transport in maintaining healthy brain function.
Abnormal amyloid-β (Aβ) aggregates are a striking feature of Alzheimer's disease (AD), and Aβ oligomers have been proven to be crucial in the pathology of AD. Any intervention targeting the ...generation or aggregation of Aβ can be expected to be useful in AD treatment. Oxidative stress and inflammation are common pathological changes in AD that are involved in the generation and aggregation of Aβ. In the present study, 6-month-old PS1V97L transgenic (Tg) mice were treated with sulforaphane, an antioxidant, for 4 months, and this treatment significantly inhibited the generation and aggregation of Aβ. Sulforaphane also alleviated several downstream pathological changes that including tau hyperphosphorylation, oxidative stress, and neuroinflammation. Most importantly, the cognition of the sulforaphane-treated PS1V97L Tg mice remained normal compared to that of wild-type mice at 10 months of age, when dementia typically emerges in PS1V97L Tg mice. Pretreating cultured cortical neurons with sulforaphane also protected against neuronal injury caused by Aβ oligomers in vitro. These findings suggest that sulforaphane may be a potential compound that can inhibit Aβ oligomer production in AD.
The observation of place cells has suggested that the hippocampus plays a special role in encoding spatial information. However, place cell responses are modulated by several nonspatial variables and ...reported to be rather unstable. Here, we propose a memory model of the hippocampus that provides an interpretation of place cells consistent with these observations. We hypothesize that the hippocampus is a memory device that takes advantage of the correlations between sensory experiences to generate compressed representations of the episodes that are stored in memory. A simple neural network model that can efficiently compress information naturally produces place cells that are similar to those observed in experiments. It predicts that the activity of these cells is variable and that the fluctuations of the place fields encode information about the recent history of sensory experiences. Place cells may simply be a consequence of a memory compression process implemented in the hippocampus.
The hippocampus is essential for spatial and episodic memory but is damaged early in Alzheimer's disease and is very sensitive to hypoxia. Understanding how it regulates its oxygen supply is ...therefore key for designing interventions to preserve its function. However, studies of neurovascular function in the hippocampus in vivo have been limited by its relative inaccessibility. Here we compared hippocampal and visual cortical neurovascular function in awake mice, using two photon imaging of individual neurons and vessels and measures of regional blood flow and haemoglobin oxygenation. We show that blood flow, blood oxygenation and neurovascular coupling were decreased in the hippocampus compared to neocortex, because of differences in both the vascular network and pericyte and endothelial cell function. Modelling oxygen diffusion indicates that these features of the hippocampal vasculature may restrict oxygen availability and could explain its sensitivity to damage during neurological conditions, including Alzheimer's disease, where the brain's energy supply is decreased.
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