Epidemiological studies reveal gender-specific differences in epilepsy. Childhood absence epilepsy (CAE), which is more prevalent in females, is characterized by typical absence seizures (ASs) consisting of brief periods of unconsciousness, associated with 2.5–4 Hz spike-wave discharges (SWDs) in the electroencephalogram (EEG). Children with CAE often present neuropsychological comorbidities, including deficits in attention and executive function. In this study, we investigated anxiety-like behaviour and memory in female Genetic Absence Epilepsy Rat from Strasbourg (GAERS), a validated model of ASs, compared to Non-Epileptic Control (NEC) and Wistar rats. We found that female GAERS generally showed normal anxiety-like behaviour relative to both control strains, although some tests suggested a reduction in anxiety. Importantly, female GAERS showed impaired spatial working memory, while recognition memory was preserved. These findings when compared with previous data in males indicate that while anxiety levels in female GAERS are preserved as those of male GAERS, memory performance differs, with males showing impairments in both spatial working memory and recognition memory. These findings emphasize the importance of considering gender differences in both clinical and preclinical epilepsy research to better understand the neuropsychological comorbidities associates with ASs. This knowledge is crucial for the identification of gender-specific mechanism, as well as the development of gender-sensitive, personalized therapies targeting both seizures and associated cognitive impairments.

BackgroundTrisomy of human chromosome 21 (Hsa21) results in a constellation of features known as Down syndrome (DS), the most common genetic form of intellectual disability. Hsa21 is orthologous to three regions in the mouse genome on mouse chromosome 16 (Mmu16), Mmu17 and Mmu10. We investigated genotype-phenotype relationships by assessing the contribution of these three regions to memory function and age-dependent cognitive decline, using three mouse models of DS, Dp1Tyb, Dp(17)3Yey, Dp(10)2Yey, that carry an extra copy of the Hsa21-orthologues on Mmu16, Mmu17 and Mmu10, respectively.HypothesisPrior research on cognitive function in DS mouse models has largely focused on models with an extra copy of the Mmu16 region and relatively little is known about the effects of increased copy number on Mmu17 and Mmu10 on cognition and how this interacts with the effects of aging. As aging is is a critical contributor to cognitive and psychiatric changes in DS, we hypothesised that ageing would differentially impact memory function in Dp1Tyb, Dp(17)3Yey, and Dp(10)2Yey, models of DS.MethodsYoung (12-13 months and old (18-20 months mice Dp1Tyb, Dp(17)3Yey and Dp(10)2Yey mice were tested on a battery of object recognition memory test that assessed object novelty detection, novel location detection and associative object-in place memory. Following behavioral testing, hippocampal and frontal cortical tissue was analysed for expression of glutamatergic receptor proteins using standard immunoblot techniques.ResultsYoung (12-13 months and old (18-20 months mice Dp1Tyb, Dp(17)3Yey and Dp(10)2Yey mice were tested on a battery of object recognition memory test that assessed object novelty detection, novel location detection and associative object-in place memory. Following behavioral testing, hippocampal and frontal cortical tissue was analysed for expression of glutamatergic receptor proteins using standard immunoblot techniques.ConclusionOur results show that distinct Hsa21-orthologous regions contribute differentially to cognitive dysfunction in DS mouse models and that aging interacts with triplication of Hsa21-orthologous genes on Mmu10.

New neurones are generated throughout life in the mammalian brain in a process known as adult hippocampal neurogenesis (AHN). Since this phenomenon grants a high degree of neuroplasticity influencing learning and memory and mood related behaviour, identifying factors that regulate AHN may be important for ameliorating age-related cognitive decline and neurodegeneration. Calorie restriction (CR), in the absence of malnutrition, has been shown to enhance AHN and improve hippocampal-dependent memory, mediated by the stomach hormone, ghrelin. Intermittent fasting (IF), a dietary strategy offering more flexibility than conventional CR, also promotes aspects of AHN. The 5:2 diet is a popular form of IF linked to a range of health benefits, however its effects on AHN and spatial memory are not well characterised. We hypothesised that the 5:2 diet would enhance AHN in a ghrelin-dependent manner. To assess this, we used immunohistochemistry to quantify new adult-born neurones and new neural stem cells (NSCs) in the hippocampal DG of adolescent and adult wild-type and mice lacking the ghrelin receptor following six weeks on a 5:2 diet. We report an age-related decline in neurogenic processes and identify a novel role for ghrelin-receptor in regulating the formation of new adult born NSCs in an age-dependent manner. However, the 5:2 diet did not affect new neurone or NSC formation in the DG. Consistent with this finding the 5:2 diet did not alter performance on a spatial learning and memory task. These data suggest that the 5:2 diet used in this study does not increase AHN or improve associated spatial memory function. Highlights 5:2 diet does not increase adult hippocampal neurogenesis 5:2 diet does not enhance spatial memory performance There is an age-related decline in adult hippocampal neurogenesis Ghrelin-receptor regulates new neural stem cell and new neurone number in an age-related manner Ghrelin-receptor is required for intact spatial memory

Typical absence seizures (ASs) are brief periods of lack of consciousness, associated with 2.5-4 Hz spike-wave discharges (SWDs) in the EEG, which are highly prevalent in children and teenagers. The majority of probands in these young epileptic cohorts show neuropsychological comorbidities, including cognitive, memory and mood impairments, even after the seizures are pharmacologically controlled. Similar cognition and memory deficits have been reported in different, but not all, genetic animal models of ASs. However, since these impairments are subtle and highly task-specific their presence may be confounded by an anxiety-like phenotype and no study has tested anxiety and memory in the same animals. Moreover, the majority of studies used non-epileptic inbred animals as the only control strain and this may have contributed to a misinterpretation of these behavioural results. To overcome these issues, here we used a battery of behavioural tests to compare anxiety and memory in the same animals from the well-established inbred model of Genetic Absence Epilepsy Rats from Strasbourg (GAERS), their inbred strain of Non-Epileptic Control (NEC) strain (that lack ASs) and normal outbred Wistar rats. We found that GAERS do not exhibit increased anxiety-like behavior and neophobia compared to both NEC and Wistar rats. In contrast, GAERS show decreased spontaneous alternation, spatial working memory and cross-modal object recognition compared to both NEC and Wistar rats. Furthermore, GAERS preferentially used egocentric strategies to perform spatial memory tasks. In summary, these results provide solid evidence of memory deficits in GAERS rats that do not depend on an anxiety or neophobic phenotype. Moreover, the presence of differences between NEC and Wistar rats stresses the need of using both outbred and inbred control rats in behavioural studies involving genetic models of ASs.

Aging and metabolic syndrome are associated with neurodegenerative pathologies including Alzheimer's disease (AD) and there is growing interest in the prophylactic potential of probiotic bacteria in this area. In this study, we assessed the neuroprotective potential of the Lab4P probiotic consortium in both age and metabolically challenged 3xTg-AD mice and in human SH-SY5Y cell culture models of neurodegeneration. In mice, supplementation prevented disease-associated deteriorations in novel object recognition, hippocampal neurone spine density (particularly thin spines) and mRNA expression in hippocampal tissue implying an anti-inflammatory impact of the probiotic, more notably in the metabolically challenged setting. In differentiated human SH-SY5Y neurones challenged with β-Amyloid, probiotic metabolites elicited a neuroprotective capability. Taken together, the results highlight Lab4P as a potential neuroprotective agent and provide compelling support for additional studies in animal models of other neurodegenerative conditions and human studies.

The Dp(10)2Yey mouse carries a ~2.3 Mb intra-chromosomal duplication of mouse chromosome 10 (Mmu10) that has homology to human chromosome 21, making it an essential model for aspects of Down syndrome (DS, trisomy 21). In this study, we investigated neuronal dysfunction in the Dp(10)2Yey mouse and report spatial memory impairment and anxiety-like behaviour alongside altered neural activity in the medial prefrontal cortex (mPFC) and hippocampus (HPC). Specifically, Dp(10)2Yeymice showed impaired spatial alternation associated with increased sharp-wave ripple activity in mPFC during a period of memory consolidation, and reduced mobility in a novel environment accompanied by reduced theta-gamma phase-amplitude coupling in HPC. Finally, we found alterations in the number of interneuron subtypes in mPFC and HPC that may contribute to the observed phenotypes and highlight potential approaches to ameliorate the effects of human trisomy 21.Funding Information: This research was funded in whole, or in part, by the Wellcome Trust.Declaration of Interests: The authors declare no competing interests.Ethics Approval Statement: All experiments were carried out under License from the UK Home Office and with Local Ethical Review Board (AWERB) approval.

Down syndrome (DS), trisomy 21, results in many complex phenotypes including cognitive deficits, heart defects and craniofacial alterations. Phenotypes arise from an extra copy of human chromosome 21 (Hsa21) genes. However, these dosage-sensitive causative genes remain unknown. Animal models enable identification of genes and pathological mechanisms. The Dp1Tyb mouse model of DS has an extra copy of 63% of Hsa21-orthologous mouse genes. In order to establish whether this model recapitulates DS phenotypes, we comprehensively phenotyped Dp1Tyb mice using 28 tests of different physiological systems and found that 468 out of 1800 parameters were significantly altered. We show that Dp1Tyb mice have wide-ranging DS-like phenotypes, including aberrant erythropoiesis and megakaryopoiesis, reduced bone density, craniofacial changes, altered cardiac function, a pre-diabetic state, and deficits in memory, locomotion, hearing and sleep. Thus, Dp1Tyb mice are an excellent model for investigating complex DS phenotype-genotype relationships for this common disorder.

This chapter provides an insight into Annette Karmiloff-Smith's thinking on her last project with the London Down Syndrome Consortium. It focuses on Annette’s interest in mouse modelling, as a further tool to help characterise atypical developmental mechanisms at multiple levels of description. London Down Syndrome Consortium is a large interdisciplinary collaboration between human geneticists, cellular biologists, psychiatrists, psychologists, neuroscientists and mouse geneticists, whose aim is to understand the link between Down syndrome and Alzheimer’s disease, and to identify protective and risk factors that could inform interventions. The mouse is a commonly used model organism in neurodevelopmental disorder research. Mouse models present an opportunity to test potential therapeutic interventions. The value of each mouse model of a neurodevelopmental disorder depends on two sorts of alignment: How well the genetics and physiology of the mouse align with the human; and How well the cognitive and behavioural phenotyping of the mouse maps to the human.

Neuronal dendritic and synaptic pruning are early features of neurodegenerative diseases, including Alzheimer’s disease. In addition to brain pathology, amyloid plaque deposition, microglial activation, and cell loss occur in the retinas of human patients and animal models of Alzheimer’s disease. Retinal ganglion cells, the output neurons of the retina, are vulnerable to damage in neurodegenerative diseases and are a potential opportunity for non-invasive clinical diagnosis and monitoring of Alzheimer’s progression. However, the extent of retinal involvement in Alzheimer’s models and how well this reflects brain pathology is unclear. Here we have quantified changes in retinal ganglion cells dendritic structure and hippocampal dendritic spines in three well-studied Alzheimer’s mouse models, Tg2576, 3xTg-AD and APP NL-G-F . Dendritic complexity of DiOlistically labelled retinal ganglion cells from retinal explants was reduced in all three models in an age-, gender-, and receptive field-dependent manner. DiOlistically labelled hippocampal slices showed spine loss in CA1 apical dendrites in all three Alzheimer’s models, mirroring the early stages of neurodegeneration as seen in the retina. Morphological classification showed that loss of thin spines predominated in all. The demonstration that retinal ganglion cells dendritic field reduction occurs in parallel with hippocampal dendritic spine loss in all three Alzheimer’s models provide compelling support for the use of retinal neurodegeneration. As retinal dendritic changes are within the optical range of current clinical imaging systems (for example optical coherence tomography), our study makes a case for imaging the retina as a non-invasive way to diagnose disease and monitor progression in Alzheimer’s disease.

Assessment of outcome in preclinical studies of vascular cognitive impairment (VCI) is heterogenous. Through an ARUK Scottish Network supported questionnaire and workshop (mostly UK-based researchers), we aimed to determine underlying variability and what could be implemented to overcome identified challenges. Twelve UK VCI research centres were identified and invited to complete a questionnaire and attend a one-day workshop. Questionnaire responses demonstrated agreement that outcome assessments in VCI preclinical research vary by group and even those common across groups, may be performed differently. From the workshop, 6 themes were discussed: issues with preclinical models, reasons for choosing functional assessments, issues in interpretation of functional assessments, describing and reporting functional outcome assessments, sharing resources and expertise, and standardization of outcomes. Eight consensus points emerged demonstrating broadly that the chosen assessment should reflect the deficit being measured and therefore, that one assessment does not suit all models; guidance/standardisation on recording VCI outcome reporting is needed and that uniformity would be aided by a platform to share expertise, material, protocols and procedures thus reducing heterogeneity and so increasing potential for collaboration, comparison and replication. As a result of the workshop, UK wide consensus statements were agreed and future priorities for preclinical research identified.

AbstractA healthy mitochondrial network is essential for the maintenance of neuronal synaptic integrity. Mitochondrial and metabolic dysfunction contributes to the pathogenesis of many neurodegenerative diseases including dementia. OPA1 is the master regulator of mitochondrial fusion and fission and is likely to play an important role during neurodegenerative events. To explore this, we quantified hippocampal dendritic and synaptic integrity and the learning and memory performance of aged Opa1 haploinsufficient mice carrying the Opa1Q285X mutation (B6; C3-Opa1Q285STOP; Opa1+/−). We demonstrate that heterozygous loss of Opa1 results in premature age-related loss of spines in hippocampal pyramidal CA1 neurons and a reduction in synaptic density in the hippocampus. This loss is associated with subtle memory deficits in both spatial novelty and object recognition. We hypothesize that metabolic failure to maintain normal neuronal activity at the level of a single spine leads to premature age-related memory deficits. These results highlight the importance of mitochondrial homeostasis for maintenance of neuronal function during ageing.

A healthy mitochondrial network is essential for the maintenance of neuronal synaptic integrity. Mitochondrial and metabolic dysfunction contributes to the pathogenesis of many neurodegenerative diseases including dementia. OPA1 is the master regulator of mitochondrial fusion and fission and is likely to play an important role during neurodegenerative events. To explore this, we quantified hippocampal dendritic and synaptic integrity and the learning and memory performance of aged Opa1 haploinsufficient mice carrying the Opa1 mutation (B6; C3-Opa1; Opa1þ/ ). We demonstrate that heterozygous loss of Opa1 results in premature age-related loss of spines in hippocampal pyramidal CA1 neurons and a reduction in synaptic density in the hippocampus. This loss is associated with subtle memory deficits in both spatial novelty and object recognition. We hypothesize that metabolic failure to maintain normal neuronal activity at the level of a single spine leads to premature age-related memory deficits. These results highlight the importance of mitochondrial homeostasis for maintenance of neuronal function during ageing.

Altered neural dynamics in the medial prefrontal cortex (mPFC) and hippocampus may contribute to cognitive impairments in the complex chromosomal disorder Down syndrome (DS). Here, we demonstrate non-overlapping behavioral differences associated with distinct abnormalities in hippocampal and mPFC electrophysiology during a canonical spatial working memory task in three partially trisomic mouse models of DS (Dp1Tyb, Dp10Yey, and Dp17Yey) that together cover all regions of homology with human chromosome 21 (Hsa21). Dp1Tyb mice show slower decision-making (unrelated to the gene dose of DYRK1A, which has been implicated in DS cognitive dysfunction) and altered theta dynamics (reduced frequency, increased hippocampal-mPFC coherence, and increased modulation of hippocampal high gamma); Dp10Yey mice show impaired alternation performance and reduced theta modulation of hippocampal low gamma; and Dp17Yey mice are not significantly different from the wild type. These results link specific hippocampal and mPFC circuit dysfunctions to cognitive deficits in DS models and, importantly, map them to discrete regions of Hsa21.

The Amyloid Cascade Hypothesis has dominated research into the causes and potential treatments of Alzheimer's Disease (AD) for nearly 30 years. Despite this, we do not have a thorough understanding of the physiological function of amyloid beta (Aβ). It is possible that Aβ has an important role in healthy brain activity, independent of its putative initiation of Alzheimer's pathology. Therefore, early stage treatments reducing Aβ concentrations in pre-symptomatic stages of dementia may be detrimental to cognition. Alzheimer treatments have included inhibition of enzymes which cleave the peptide from Amyloid Precursor Protein (APP). However, this also inhibits cleavage of other substrates, potentially causing off target effects. We have developed a monoclonal anti-APP antibody (2B3) that binds to the beta-cleavage site of Aβ, sterically blocking APP cleavage. It has previously reduced Aβ levels in primary cortical neurons of an AD mouse model. In this study we used 2B3 to exhibit a selective inhibition of Aβ in wild-type mice to investigate the effect on cognition. Performance of 5-month-old C57Bl/6 mice in novel object recognition (NOR) and object in place (OiP) tasks was assessed before and during chronic intracerebroventricular (icv) administration of either 2B3 or control antibody, in a counterbalanced design. Performance did not change for either group after surgery for the NOR task. However, in the OiP task there was a significant decrease in exploration of novel object-place associations for the 2B3 group relative to the control group after surgery (P=0.014). Immunohistochemical analysis revealed that 2B3 diffused throughout the hippocampus but did not penetrate to the cortex. Subsequent work will examine APP products in WT mice and explore the impact of 2B3 on synaptic mechanisms of memory in the hippocampus. The deficit in cognitive performance for the OiP task, but not the NOR task suggested an effect on the antibody of 2B3 on hippocampal information processing. This work supports evidence that inhibition of Aβ impairs synaptic plasticity and impacts memory function in normal mice. It is important that more research is done to elucidate the role of this peptide, particularly considering that many putative treatments for AD have involved inhibiting this pathway.

Three experiments examined the ability of mice to forage efficiently for liquid rewards in pots located in an open field arena. Search behaviour was unconstrained other than by the walls of the arena. All mice acquired the task within 4 days of training, with one trial per day. Experiment 1 tested the hypothesis that hippocampal lesions would disrupt foraging behaviour using extramaze cues. Mice with hippocampal lesions showed normal latency to initiate foraging and to complete the task relative to sham-operated mice. However, lesioned mice showed increased perseverative responding (sensitization) to recently rewarded locations, increased total working memory errors and an increased propensity to search near previously rewarded locations. In Experiment 2, the extramaze cues were obscured and each pot was identified by a unique pattern. Under these conditions, mice with hippocampal lesions showed comparable working memory errors to control mice. However, lesioned mice continued to display increased perseverative responding and altered search strategies. Experiment 3 tested the hypothesis that age-related accumulation of amyloid would disrupt foraging behaviour in transgenic PDAPP mice expressing the V717F amyloid precursor protein (APP) mutation. Consistent with previous findings, PDAPP mice showed both age-dependent and age-independent behavioural changes. More specifically, 14-16 month-old PDAPP mice showed a deficit in perseverative responding and working memory errors. In contrast, changes in search behaviour, such as systematic circling, were present throughout development. The latter indicates that APP overexpression contributed to some features of the PDAPP behavioural phenotype, whereas working memory and flexible responding was sensitive to ageing and beta-amyloid burden. In conclusion, the present study provided novel insight into the role of the hippocampus and the effects of APP overexpression on memory and search behaviour in an open-field foraging task.

Hyperactivity of the classical axis of the renin-angiotensin system (RAS), caused by angiotensin II (Ang II)-mediated activation of the angiotensin II type 1 receptor (AT1R), is implicated in the pathogenesis of Alzheimer's disease (AD). Dysregulation of angiotensin-converting enzyme-2 (ACE-2), that degrades Ang II and counter-regulates the classical RAS pathway, has been implicated in AD. This project tested the hypothesis that enhanced ACE2 activity would improve cognitive and pathological measures in Tg2576 mice Experiment 1 assessed whether 30 days administration of an ACE2 activator (diaminazene aceturate (DIZE)) at 15mg/kg/day by intraperitoneal (IP) injection could improve cognitive performance in 13-14-month-old Tg2576 mice (n=10). Experiment 2 assessed whether long-term (10 weeks; n=11) and/or acute (10 days; n=17) treatment with DIZE could prevent the onset of cognitive impairment in 12-13 months of age. WT (n=11, n=20) and Tg2576 mice (n=11, n=17) were also administered vehicle control in experiment 1 and 2 respectively. Associative recognition memory was assessed before and after DIZE administration using an object-in- place (OiP) task. Enzyme activity and levels of RAS pathway metabolites, as well as amyloid-β (Aβ) 40, 42 and 43 levels were determined by ELISA. Neuroinflammatory markers were assessed by western blot. Experiment 1: Tg2576 mice showed a significant improvement in OiP memory following DIZE administration (compared to vehicle treated Tg2576 mice). Hippocampal ACE2 activity was significantly increased in DIZE-administered Tg2576 mice compared to Tg-Vehicle (P<0.05) and WT mice (P<0.05). Experiment 2: Vehicle-administered Tg2576 mice showed an age-related impairment in OiP performance from 9-10 months to 12-13 months of age (p<0.001). However neither Tg2576 mice administered DIZE for 10 weeks across the same age-range or a Tg2576 group given DIZE for 10 days prior to testing at 12-13 months of age, showed a significant decline in performance (p's>0.05) nor a significant difference relative to WT vehicle performance (p>0.05). Aβ levels and inflammatory markers are currently being analysed. Increasing the activity of ACE2 in Tg2576 mice both reversed and protected against cognitive impairment. Normalising the hyperactivity of the classical RAS axis by activation of ACE2 may provide a promising therapeutic target for the treatment of early stage AD.

The perirhinal cortex (PRH) is considered a crucial cortical area for familiarity memory and electrophysiological studies have reported the presence of visual familiarity encoding neurons in PRH. However, recent evidence has questioned the existence of these neurons. Here, we used a visual task in which head-restrained mice were passively exposed to oriented gratings or natural images. Evoked potentials and single-unit recordings showed evoked responses to novelty in V1 under some conditions. However, the PRH showed no response modulation with respect to familiarity under a variety of different conditions or retention delays. These results indicate that the PRH does not contribute to familiarity/novelty encoding using passively exposed visual stimuli.

The conditions under which the hippocampus contributes to learning about spatio-temporal configural patterns are not fully established. The aim of Experiments 1-4 was to investigate the impact of hippocampal lesions on learning about where or when a reinforcer would be delivered. In each experiment, the rats received exposure to an identical set of patterns (i.e., spotted + morning, checked + morning, spotted + afternoon and checked + afternoon); and the contexts (Experiment 1), times of day (Experiment 2), or their configuration (Experiments 3 and 4) signalled whether or not a reinforcer would be delivered. The fact that hippocampal damage did not disrupt the formation of simple or configural associations involving spatio-temporal patterns is surprising, and suggests that the contribution of the hippocampus is restricted to mediated learning (or updating) involving spatio-temporal configurations. (C) 2017 Elsevier Inc. All rights reserved.

Successful retrieval of a memory for an entire pattern of stimulation by the presentation of a fragment of that pattern is a critical facet of memory function. We examined processes of pattern completion using novel sensory preconditioning procedures in rats that had either received sham lesions (group Sham) or lesions of the hippocampus (group HPC). After exposure to two audio-visual patterns (AX and BY) rats received fear conditioning with X (but not Y). Subsequent tests assessed fear to stimulus compounds (e.g., AX versus BX; Experiment 1) or elements (A versus B; Experiment 2). There was more fear to AX than BX in group Sham but not group HPC, while there was more fear to A than B in group HPC, but not in group Sham. This double dissociation suggests that pattern completion can be based upon separable processes that differ in their reliance on the hippocampus.