Virtual Morris water maze: opportunities and challenges

Behavioural interference at event boundaries reduces long-term memory performance in the virtual water maze task without affecting working memory performance

Narrative episodic memory of movie clips can be retroactively impaired by presenting unrelated stimuli coinciding with event boundaries. This effect has been linked with rapid hippocampal processes triggered by the offset of the event, that are alternatively related either to memory consolidation or with working memory processes. Here we tested whether this effect extended to spatial memory, the temporal specificity and extent of the interference, and its effect on working- vs long-term memory. In three computerized adaptations of the Morris Water Maze, participants learned the location of an invisible target over three trials each. A second spatial navigation task was presented either immediately after finding the target, after a 10-s delay, or no second task was presented (control condition). A recall session, in which participants indicated the learned target location with 10 'pin-drop' trials for each condition, was performed after a 1-h or a 24-h break. Spatial memory was measured by the mean distance between pins and the true location. Results indicated that the immediate presentation of the second task led to worse memory performance, for both break durations, compared to the delayed condition. There was no difference in performance between the delayed presentation and the control condition. Despite this long-term memory effect, we found no difference in the rate of performance improvement during the learning session, indicating no effect of the second task on working memory. Our findings are in line with a rapid process, linked to the offset of an event, that is involved in the early stages of memory consolidation.

Moxibustion Promoted Axonal Regeneration and Improved Learning and Memory of Post-stroke Cognitive Impairment by Regulating PI3K/AKt and TACC3

BACKGROUND

This study aimed to investigate whether moxibustion could affect PI3K/Akt pathway to regulate Transforming acidic coiled-coil containing protein 3 (TACC3) and promote axonal regeneration to improve learning and memory function in middle cerebral artery occlusion (MCAO) rats.

METHODS

Sixty SD rats were randomly divided into 4 groups: sham-operated control group (SC), model control group (MC), model + moxibustion group (MM), and model + inhibitor + moxibustion group (MIM). The rats in MC, MM, and MIM groups were made into MCAO models, and PI3K inhibitor LY294002 was injected into the rats in MIM group before modeling; while the rats in SC group were only treated with artery separation without monofilament inserting. After that, the rats in MM and MIM groups were intervented with moxibustion. We used the Zea-Longa scale, micro-Magnetic Resonance Imaging (micro-MRI), Morris water maze (MWM), TUNEL, western blot (WB), immunofluorescence and immunohistochemistry to evaluate the neurological deficits, cerebral infarct volume, learning and memory, apoptotic cell percentage in the hippocampal, the expression level of axonal regeneration and PI3K/AKt related proteins, the expression level of TACC3. The detection of 2 h after surgery showed the result before moxibustion and 7 days after the intervention showed the results after moxibustion.

RESULTS

After 7 d of intervention, the scores of Zea-Longa and the cerebral infarct volume, the escape latency, the percentage of apoptosis cells of MM group were lower than that of MC and MIM groups; the frequency of rats crossed the previous platform location, PI3K, p-Akt/t-Akt and TACC3, the level of GAP-43 in MM group was more than MC and MIM groups (P < 0.05). While no statistical difference existed between MIM group and MC group (P > 0.05).

CONCLUSION

Moxibustion can promote axonal regeneration and improve learning and memory of Post-stroke cognitive impairment via activating the PI3K/AKT signaling pathway and TACC3.

Ameliorative effect of Nyctanthes arbor-tristis L. by suppression of pentylenetetrazole-induced kindling in mice: An insight from EEG, neurobehavioral and in-silico studies

Epilepsy is an abiding condition associated with recurrent seizure attacks along with associated neurological and psychological emanation owing to disparity of excitatory and inhibitory neurotransmission. The current study encompasses the assessment of the Nyctanthes arbor-tristis L. methanolic extract (Na.Cr) in the management of convulsive state and concomitant conditions owing to epilepsy. The latency of seizure incidence was assessed using pentylenetetrazol (PTZ) kindling models along with EEG in Na.Cr pretreated mice, trailed by behavior assessment (anxiety and memory), biochemical assay, histopathological alterations, chemical profiling through GCMS, and molecular docking. The chronic assessment of PTZ-induced kindled mice depicted salvation in a dose-related pattern and outcomes were noticeable with extract at 400 mg/kg. The extract at 400 mg/kg defends the progress of kindling seizures and associated EEG. Co-morbid conditions in mice emanating owing to epileptic outbreaks were validated by behavioral testing and the outcome depicted a noticeable defense related to anxiety (P<0.001) and cognitive deficit (P<0.001) at 400 mg/kg. The isolated brains were evaluated for oxidative stress and the outcome demonstrated a noticeable effect in a dose-dependent pattern. Treatment with Na.Cr. also preserved the brain from PTZ induced neuronal damage as indicated by histopathological analysis. Furthermore, the GCMS outcome predicted 28 compounds abundantly found in the plant. The results congregated in the current experiments deliver valued evidence about the defensive response apportioned by Na.Cr which might be due to decline in oxidative stress, AChE level, and GABAergic modulation. These activities may contribute to fundamental pharmacology and elucidate some mechanisms behind the activities of Nyctanthes arbor-tristis.

Investigating the effects of age and prior military service on fluid and crystallized cognitive functions using virtual morris water maze (vMWM) and NIH Toolbox tasks

Much of current knowledge of aging involves war veterans and research about age-related cognitive changes in veterans involves generalized or single function tests or health or neurological disorders. The current study examined military service within the context of comparisons of young and old humans involving generally healthy individuals to address normal age-associated cognitive changes. Adult participants included 11 young females (8 non-veterans; 3 veterans; 21-31 years), 5 young males (non-veterans, 21-24 years), 9 older females (non-veterans, 62-80 years), and 21 older males (11 non-veterans; 10 veterans; 60-86 years). They were tested in virtual Morris water maze (vMWM) tasks, which were designed to test spatial learning, cognitive flexibility and working memory, similar to rodent studies, and were validated by correlations with specific NIH Toolbox (NIH-TB) Cognitive Battery or Wechsler Memory Scale (WMS) Logical Memory I and II tests. Significant age-related deficits were seen on multiple vMWM tasks and NIH-TB fluid cognition tasks. Among older males, vMWM tasks appeared to be more sensitive, based on finding statistical differences, to prior military service than NIH Toolbox tasks. Compared with male non-veterans of comparable age and younger, older male veterans exhibited significant deficits in spatial learning, cognitive flexibility, and working memory on vMWM tasks. Our findings support continued development and characterization of vMWM tasks that are comparable between rodents and humans for translating aging interventions between species, and provide impetus for larger investigations examining the extent to which prior military service can serve as a "hidden" variable in normal biological declines of cognitive functions.

Dexmedetomidine alleviates hippocampal neuronal loss and cognitive decline in rats undergoing open surgery under sevoflurane anaesthesia by suppressing CCAAT/enhancer-binding protein beta

Dexmedetomidine (Dex) may exert neuroprotective effects by attenuating inflammatory responses. However, whether Dex specifically improves postoperative cognitive dysfunction (POCD) by inhibiting microglial inflammation through what pathway remains unclear. In this study, the POCD model was constructed by performing open surgery after 3 h of continuous inhalation of 3% sevoflurane to rats, which were intraperitoneally injected with 25 μg/kg Dex .5 h before anaesthesia. The results displayed that Dex intervention decreased rat escape latency, maintained swimming speed and increased the number of times rats crossed the platform and the time spent in the target quadrant. Furthermore, the rat neuronal injury was restored, alleviated POCD modelling-induced rat hippocampal microglial activation and inhibited microglial M1 type polarization. Besides, we administered Dex injection and/or CCAAT/enhancer-binding protein beta (CEBPB) knockdown on the basis of sevoflurane exposure and open surgery and found that CEBPB was knocked down, resulting in the inability of Dex to function, which confirmed CEBPB as a target for Dex treatment. To sum up, Dex improved POCD by considering CEBPB as a drug target to activate the c-Jun N-terminal kinase (JNK)/p-38 signaling pathway, inhibiting microglial M1 polarization-mediated inflammation in the central nervous system.

Tu-Xian Decoction ameliorates diabetic cognitive impairment by inhibiting DAPK-1

Tu-Xian decoction (TXD), a traditional Chinese medicine (TCM) formula, has been frequently administered to manage diabetic cognitive impairment (DCI). Despite its widespread use, the mechanisms underlying TXD's protective effects on DCI have yet to be fully elucidated. As a significant regulator in neurodegenerative conditions, death-associated protein kinase-1 (DAPK-1) serves as a focus for understanding the action of TXD. This study was designed to whether TXD mediates its beneficial outcomes by inhibiting DAPK-1. To this end, a diabetic model was established using Sprague-Dawley (SD) rats through a high-fat, high-sugar (HFHS) diet regimen, followed by streptozotocin (STZ) injection. The experimental cohort was stratified into six groups: Control, Diabetic, TC-DAPK6, high-dose TXD, medium-dose TXD, and low-dose TXD groups. Following a 12-week treatment period, various assessments-including blood glucose levels, body weight measurements, Morris water maze (MWM) testing for cognitive function, brain magnetic resonance imaging (MRI), and histological analyses using hematoxylin-eosin (H&E), and Nissl staining-were conducted. Protein expression in the hippocampus was quantified through Western blotting analysis. The results revealed that TXD significantly improved spatial learning and memory abilities, and preserved hippocampal structure in diabetic rats. Importantly, TXD administration led to a down-regulation of proteins indicative of neurological damage and suppressed DAPK-1 activity within the hippocampal region. These results underscore TXD's potential in mitigating DCIvia DAPK-1 inhibition, positioning it as a viable therapeutic candidate for addressing this condition. Further investigation into TXD's molecular mechanisms may elucidate new pathways for the treatment of DCI.

Examining individual learning patterns using generalised linear mixed models

Everyone learns differently, but individual performance is often ignored in favour of a group-level analysis. Using data from four different experiments, we show that generalised linear mixed models (GLMMs) and extensions can be used to examine individual learning patterns. Producing ellipsoids and cluster analyses based on predicted random effects, individual learning patterns can be identified, clustered and used for comparisons across various experimental conditions or groups. This analysis can handle a range of datasets including discrete, continuous, censored and non-censored, as well as different experimental conditions, sample sizes and trial numbers. Using this approach, we show that learning a face-named paired associative task produced individuals that can learn quickly, with the performance of some remaining high, but with a drop-off in others, whereas other individuals show poor performance throughout the learning period. We see this more clearly in a virtual navigation spatial learning task (NavWell). Two prominent clusters of learning emerged, one showing individuals who produced a rapid learning and another showing a slow and gradual learning pattern. Using data from another spatial learning task (Sea Hero Quest), we show that individuals' performance generally reflects their age category, but not always. Overall, using this analytical approach may help practitioners in education and medicine to identify those individuals who might need extra help and attention. In addition, identifying learning patterns may enable further investigation of the underlying neural, biological, environmental and other factors associated with these individuals.

Spatial navigation: Alzheimer's pathology disrupts movement-based navigation

All animals use two different strategies to navigate: idiothetic or movement-based navigation, and allothetic or landmark-based navigation. A new study reveals that compromised idiothetic navigation underlies disrupted grid cell coding in an early stage Alzheimer's disease mouse model.

Virtual Reality for Spatial Navigation

Immersive virtual reality (VR) allows its users to experience physical space in a non-physical world. It has developed into a powerful research tool to investigate the neural basis of human spatial navigation as an embodied experience. The task of wayfinding can be carried out by using a wide range of strategies, leading to the recruitment of various sensory modalities and brain areas in real-life scenarios. While traditional desktop-based VR setups primarily focus on vision-based navigation, immersive VR setups, especially mobile variants, can efficiently account for motor processes that constitute locomotion in the physical world, such as head-turning and walking. When used in combination with mobile neuroimaging methods, immersive VR affords a natural mode of locomotion and high immersion in experimental settings, designing an embodied spatial experience. This in turn facilitates ecologically valid investigation of the neural underpinnings of spatial navigation.

A virtual reality platform for memory evaluation: Assessing effects of spatial strategies

Human spatial memories are usually evaluated using computer screens instead of real arenas or landscapes where subjects could move voluntarily and use allocentric cues to guide their behavior. A possible approach to fill this gap is the adoption of virtual reality, which provides the opportunity to create spatial memory tasks closer to real-life experience. Here we present and evaluate a new software to create experiments using this technology. Specifically, we have developed a spatial memory task that is carried out in a computer-assisted virtual environment where participants walk around a virtual arena using a joystick. This spatial memory task provides an immersive environment where the spatial component is constantly present without the use of virtual reality goggles. The design is similar to that of tasks used for animal studies, allowing a direct comparison across species. We found that only participants who reported using spatial cues to guide their behavior showed significant learning and performed significantly better during a memory test. This tool allows evaluation of human spatial memory in an ecological environment and will be useful to develop a wide range of other tasks to assess spatial cognition.

Application of Real and Virtual Radial Arm Maze Task in Human

Virtual Reality (VR) emerges as a promising technology capable of creating different scenarios in which the body, environment, and brain are closely related, proving enhancements in the diagnosis and treatment of several spatial memory deficits. In recent years, human spatial navigation has increasingly been studied in interactive virtual environments. However, navigational tasks are still not completely adapted in immersive 3D VR systems. We stipulate that an immersive Radial Arm Maze (RAM) is an excellent instrument, allowing the participants to be physically active within the maze exactly as in the walking RAM version in reality modality. RAM is a behavioral ecological task that allows the analyses of different facets of spatial memory, distinguishing declarative components from procedural ones. In addition to describing the characteristics of RAM, we will also analyze studies in which RAM has been used in virtual modality to provide suggestions into RAM building in immersive modality.