A Preclinical Model of Computerized Cognitive Training: Touchscreen Cognitive Testing Enhances Cognition and Hippocampal Cellular Plasticity in Wildtype and Alzheimer's Disease Mice

Cognition enhances cognition: A comprehensive analysis on cognitive stimulation protocols and their effects on cognitive functions in animal models

Brain plasticity is involved in the regulation of neural differentiation as well as in functional processes related to memory consolidation, learning, and cognition during healthy life and brain pathology. Modifications in lifestyle, like poor diet, insufficient physical exercise and cognitive stimulation are associated with an increased risk of neurodegeneration; however, there is a paucity of research regarding the impact of individual factors on dementia risk or progression. Cognitive stimulation is a group of techniques and strategies, including cognitive enrichment (CE) and cognitive training (CT), aimed to maintain or improve the functionality of cognitive abilities, such as memory, learning, cognitive flexibility, and attention. The present scoping review focuses on cognitive stimulation by investigating its neuroprotective and therapeutic role on these cognitive functions in rodents. A methodical bibliographic search of experimental studies on rats and mice was conducted on PubMed and Scopus databases up to June 3, 2024. A pool of 29 original research articles was considered as relevant to the topic of the present work. Evidence shows that CE but above all CT influence cognitive performance and brain structure in rodents with specific differences with respect to the quality and quantity of stimulation. There would appear to be greater effects in restoring damage than in preserving or improving a functioning condition. These results provide a theoretical basis to be considered in the therapeutic setting, although further systematic studies would be necessary to identify and characterize the cognitive stimulation protocols which hold the greatest and task-transferable impact on cognitive functioning and maintenance.

Development of A New Scoring System in Higher Animals for Testing Cognitive Function in the Newborn Period: Effect of Prenatal Hypoxia-Ischemia

Introduction Enhanced models for assessing cognitive function in the neonatal period are imperative in higher animals. Postnatal motor deficits, characteristic of cerebral palsy, emerge in newborn kits within our prenatal-rabbit model of hypoxia-ischemia (HI). In humans, prenatal HI leads to intellectual disability and cerebral palsy. In a study examining cognitive function in newborn rabbits, we explored several questions. Is there a distinction between conditioned and unconditioned kits? Can the kits discern the human face or the lab coat? Do motorically-normal kits, born after prenatal HI, exhibit cognitive deficits? Methods The conditioning protocol was randomly assigned to kits from each litter. For conditioning, the same human, wearing a lab coat, fed the rabbit kits for 9 days before the cognitive test. The 6-arm radial maze was chosen for its simplicity and ease of use. Normally appearing kits, born after uterine ischemia at 79% or 92% term in New Zealand White rabbits, were compared to Naïve kits. On postpartum day 22/23 or 29/30, the 6-arm maze helped determine if the kits recognized the original feeder from bystander (Test-1) or the lab coat on bystander (Test-2). The use of masks of feeder/bystander (Test-3) assessed confounding cues. A weighted score was devised to address variability in entry to maze arms, time, and repeated-trial learning. Results In conditioned kits, both Naïve and HI kits exhibited a significant preference for the face of the feeder, but not the lab coat. Cognitive deficits were minimal in normal-appearing HI kits. Conclusion The weighted score system was amenable to statistical manipulation.

Cognitive trajectories in longitudinally trained 3xTg-AD mice

Preclinical studies in Alzheimer's disease (AD) often rely on cognitively naïve animal models in cross-sectional designs that can fail to reflect the cognitive exposures across the lifespan and heterogeneous neurobehavioral features observed in humans. To determine whether longitudinal cognitive training may affect cognitive capacities in a well-characterized AD mouse model, 3xTg and wild-type mice (n = 20) were exposed daily to a training variant of the Go-No-Go (GNG) operant task from 3 to 9 months old. At 3, 6, and 9 months, performance on a testing variant of the GNG task and anxiety-like behaviors were measured, while long-term recognition memory was also assessed at 9 months. In general, GNG training improved performance with increasing age across genotypes. At 3 months old, 3xTg mice showed slight deficits in inhibitory control that were accompanied by minor improvements in signal detection and decreased anxiety-like behavior, but these differences did not persist at 6 and 9 months old. At 9 months old, 3xTg mice displayed minor deficits in signal detection, and long-term recognition memory capacity was comparable with wild-type subjects. Our findings indicate that longitudinal cognitive training can render 3xTg mice with cognitive capacities that are on par with their wild-type counterparts, potentially reflecting functional compensation in subjects harboring AD genetic mutations.

Longitudinal assessment of cognitive function in the APPswe/PS1dE9 mouse model of Alzheimer's-related beta-amyloidosis

Preclinical models of Alzheimer's disease (AD)-related cognitive decline can be useful for developing therapeutics. The current study longitudinally assessed short-term memory, using a delayed matching-to-position (DMTP) task, and attention, using a 3-choice serial reaction time (3CSRT) task, from approximately 18 weeks of age through death or 72 weeks of age in APPswe/PS1dE9 mice, a widely used mouse model of AD-related amyloidosis. Both transgenic (Tg) and non-Tg mice exhibited improvements in DMTP accuracy over time. Breaks in testing reduced DMTP accuracy but accuracy values quickly recovered in both Tg and non-Tg mice. Both Tg and non-Tg mice exhibited high accuracy in the 3CSRT task with breaks in testing briefly reducing accuracy values equivalently in the 2 genotypes. The current results raise the possibility that deficits in Tg APPswe/PS1dE9 mice involve impairments in learning rather than declines in established performances. A better understanding of the factors that determine whether deficits develop will be useful for designing evaluations of potential pharmacotherapeutics and may reveal interventions for clinical application.

Insulin and Disorders of Behavioural Flexibility

Behavioural inflexibility is a symptom of neuropsychiatric and neurodegenerative disorders such as Obsessive-Compulsive Disorder, Autism Spectrum Disorder and Alzheimer's Disease, encompassing the maintenance of a behaviour even when no longer appropriate. Recent evidence suggests that insulin signalling has roles apart from its regulation of peripheral metabolism and mediates behaviourally-relevant central nervous system (CNS) functions including behavioural flexibility. Indeed, insulin resistance is reported to generate anxious, perseverative phenotypes in animal models, with the Type 2 diabetes medication metformin proving to be beneficial for disorders including Alzheimer's Disease. Structural and functional neuroimaging studies of Type 2 diabetes patients have highlighted aberrant connectivity in regions governing salience detection, attention, inhibition and memory. As currently available therapeutic strategies feature high rates of resistance, there is an urgent need to better understand the complex aetiology of behaviour and develop improved therapeutics. In this review, we explore the circuitry underlying behavioural flexibility, changes in Type 2 diabetes, the role of insulin in CNS outcomes and mechanisms of insulin involvement across disorders of behavioural inflexibility.

Repeated performance of spatial memory tasks ameliorates cognitive decline in APP/PS1 mice

BACKGROUND

Alzheimer's disease (AD) is a burden on the public health system because it is a neurodegenerative disease that is incurable and for which there is no successful treatment. AD patients suffer from symptoms for many years, with progressive loss of cognitive and functional abilities. In addition to the features of AD, described as amyloid plaques and neurofibrillary tangles, neuroinflammatory processes, genetic factors, and lifestyle also play important roles. Increasing evidence for lifestyle factors includes possible changes due to smoking, social engagement, and physical activity.

METHODS

Morris water maze behavioral tasks were performed to analyze the formation of spatial memory. APPswe/PS1dE9 mice with a remarkable increase in amyloid-β production associated with certain behavioral abnormalities comparable to AD symptoms and age-matched wild-type littermates were trained several times at 3, 6, 9, and 12 months of age and compared with untrained groups at 9 and 12 months of age. Performance during the acquisition phase, in the reference memory test, and in searching strategies were analyzed.

RESULTS

9- and 12-month-old APP/PS1 mice showed cognitive impairment, especially in the reference memory test and searching strategies. This cognitive deterioration was reversed in 9- and 12-month-old APP/PS1 mice that had been previously trained several times. Even in the reversal test, in which memory formation must be adapted to the new platform position, several trained APP/PS1 mice performed better.

CONCLUSION

Repeated spatial memory training in the water maze showed positive effects on memory formation in APP/PS1 mice. Interestingly, the cohort that had been previously trained several times was able to use increased hippocampus-dependent strategies, similar to the WT mice. This may suggest that cognitively demanding and physically active tasks can improve cognitive function.

When left is right: The effects of paw preference training on behaviour in mice

Spontaneous limb preferences exist in numerous species. To investigate the underlying mechanisms of these preferences, different methods, such as training, have been developed to shift preferences artificially. However, studies that systematically examine the effects of shifting preferences on behaviour and physiology are largely missing. Therefore, the aim of this study was to assess the impact of shifting paw preferences via training on spontaneous home cage behaviour, as well as anxiety-like behaviour and exploratory locomotion (Elevated plus maze test, Dark light test, Open field test, Free exploration test), learning performance (Labyrinth-maze) and stress hormones (fecal corticosterone metabolites) in laboratory mice (Mus musculus f. domestica). For this, we assessed spontaneous paw preferences of C57BL/6J females (N_ambilateral = 23, N_left = 23, N_right = 25). Subsequently, half of the individuals from each category were trained once a week for four weeks in a food-reaching task to use either their left or right paw, respectively, resulting in six groups: AL, AR, LL, LR, RL, RR. After training, a battery of behavioural tests was performed and spontaneous preferences were assessed again. Our results indicate that most mice were successfully trained and the effect of training was present days after training. However, a significant difference of preferences between RL and LL mice during training suggests a rather low training success of RL mice. Additionally, preferences of L mice differed from those of A and R mice after training, indicating differential long-term effects of training in these groups. Furthermore, left paw training led to higher levels of self-grooming, possibly as a displacement behaviour, and more time spent in the light compartment of the Dark light test. However, overall, there was no systematic influence of training on behavioural measures and stress hormones. Different explanations for this lack of influence, such as the link between training and hemispheric functioning or the intensity and ecological relevance of the training, are discussed.