The retinal degeneration (rd) gene seriously impairs spatial cognitive performance in normal and Alzheimer's transgenic mice

Visuo-spatial learning and memory impairments in the 5xFAD mouse model of Alzheimer's disease: Effects of age, sex, albinism, and motor impairments

The 5xFAD mouse model of Alzheimer's disease (AD) rapidly develops AD-related neuro-behavioral pathology. Learning and memory impairments in 5xFAD mice, however, are not always replicated and the size of impairments varies considerably across studies. To examine possible sources of this variability, we analyzed the effects of age, sex, albinism due to background genes (Tyr^c , Oca2^p ) and motor impairment on learning and memory performance of wild type and 5xFAD mice on the Morris water maze, from 3 to 15 months of age. The 5xFAD mice showed impaired learning at 6-9 months of age, but memory impairments were not detected with the test procedure used in this study. Performance of 5xFAD mice was profoundly impaired at 12-15 months of age, but was accompanied by slower swim speeds than wild-type mice and a frequent failure to locate the escape platform. Overall female mice performed worse than males, and reversal learning impairments in 5xFAD mice were more pronounced in females than males. Albino mice performed worse than pigmented mice, confirming that albinism can impair performance of 5xFAD mice independently of AD-related transgenes. Overall, these results show that 5xFAD mice have impaired learning performance at 6-9 months of age, but learning and memory performance at 12-15 months is confounded with motor impairments. Furthermore, sex and albinism should be controlled to provide an accurate assessment of AD-related transgenes on learning and memory. These results will help reduce variability across pre-clinical experiments with 5xFAD mice, and thus enhance the reliability of studies developing new therapeutics for AD.

High-Fat Diet Impairs Tactile Discrimination Memory in the Mouse

Research on the impact of diet and memory has garnered considerable attention while exploring the link between obesity and cognitive impairment. High-fat diet (HFD) rodent models recapitulate the obesity phenotype and subsequent cognitive impairments. While it is known that HFD is associated with sensory impairment, little attention has been given to the potential role these sensory deficits may play in recognition memory testing, one of the most commonly used cognitive tests. Because mice utilize their facial whiskers as their primary sensory apparatus, we modified a common recognition test, the novel object recognition task, by replacing objects with sandpaper grits at ground level, herein referred to as the novel tactile recognition task (NTR). First, we tested whisker-manipulated mice in this task to determine its reliance on intact whiskers. Then, we tested the HFD mouse in the NTR. Finally, to ensure that deficits in the NTR are due to cognitive impairment and not HFD-induced sensory deficiencies, we tested the whisker sensitivity of HFD mice via the corner test. Our results indicate that the NTR is a whisker dependent task, and that HFD mice exhibit tactile recognition memory impairment, not accompanied by whisker sensory deficits.

Gait Ignition Failure in JNPL3 Human Tau-mutant Mice

Cognitive impairments and motor dysfunction are commonly observed behavioral phenotypes in genetic animal models of neurodegenerative diseases. JNPL3 transgenic mice expressing human P301L-mutant tau display motor disturbances with age- and gene dose-dependent development of neurofibrillary tangles, suggesting that tau pathology causes neurodegeneration associated with motor behavioral abnormalities. Although gait ignition failure (GIF), a syndrome marked by difficulty in initiating locomotion, has been described in patients with certain forms of tauopathies, transgenic mouse models mirroring human GIF syndrome have yet to be reported. Using the open field and balance beam tests, here we discovered that JNPL3 homozygous mice exhibit a marked delay of movement initiation. The elevated plus maze excluded the possibility that hesitation to start in JNPL3 mice was caused by enhanced levels of anxiety. Considering the normal gait ignition in rTg4510 mice expressing the same mutant tau in the forebrain, GIF in JNPL3 mice seems to arise from abnormal tau deposition in the hindbrain areas involved in locomotor initiation. Accordingly, immunohistochemistry revealed highly phosphorylated paired helical filament tau in JNPL3 brainstem areas associated with gait initiation. Together, these findings demonstrate a novel behavioral phenotype of impaired gait initiation in JNPL3 mice and underscore the value of this mouse line as a tool to study the neural mechanisms and potential treatments for human GIF syndrome.

Assessment of spatial learning and memory in the Barnes maze task in rodents-methodological consideration

Among the methods valuable for assessing spatial learning and memory impairments in rodents, the Barnes maze (BM) task deserves special attention. It is based on the assumption that the animal placed into the aversive environment should learn and remember the location of an escape box located below the surface of the platform. Different phases of the task allow to measure spatial learning, memory retrieval, and cognitive flexibility. Herein, we summarize current knowledge about the BM procedure, its variations and critical parameters measured in the task. We highlight confounding factors which should be taken into account when conducting BM task, discussing briefly its advantages and disadvantages. We then propose an extended version of the BM protocol which allows to measure different aspects of spatial learning and memory in rodents. We believe that this review will help to standardize the BM methodology across the laboratories and eventually make the results comparable.

Locomotor activity, emotionality, sensori-motor gating, learning and memory in the APPswe/PS1dE9 mouse model of Alzheimer's disease

The APPswe/PS1dE9 mouse (line 85) is a double transgenic model of Alzheimer's disease (AD) with familial amyloid precursor protein and presenilin-1 mutations. These mice develop age-related behavioral changes reflective of the neuropsychiatric symptoms (altered anxiety-like behaviour, hyperactivity) and cognitive dysfunction (impaired learning and memory) observed in AD. The APPswe/PS1dE9 mouse has been used to examine the efficacy of therapeutic interventions on behaviour, despite previous difficulties in replicating behavioural phenotypes. Therefore, the purpose of this study was to establish the reliability of these phenotypes by further characterizing the behaviour of male APPswe/PS1dE9 and wild-type mice between 7 and 14 months of age. Mice were tested on the open-field over 5-days to examine emotionality, locomotor activity and inter-session habituation. Mice were also tested on the repeated-reversal water maze task and spontaneous alternation on the Y-maze to assess working memory. Sensori-motor gating was examined with acoustic startle and pre-pulse inhibition. Lastly contextual and cued (trace) memory was assessed with fear conditioning. The results show that among non-cognitive behaviours, APPswe/PS1dE9 mice have normal locomotor activity, anxiety-like behavior, habituation and sensori-motor gating. However, APPswe/PS1dE9 mice show impaired working memory on the repeated-reversal water-maze and impaired memory in contextual but not trace-cued fear conditioning. These results indicate that the APPswe/PS1dE9 (line 85) mice have deficits in some types of hippocampal-dependent learning and memory and, at the ages tested, APPswe/PS1dE9 mice model cognitive dysfunction but not neuropsychiatric symptoms.

Behavioural Phenotyping of APPswe/PS1δE9 Mice: Age-Rrelated Changes and Effect of Long-Term Paroxetine Treatment

Alzheimer’s disease (AD) is a devastating illness characterized by a progressive loss of cognitive, social, and emotional functions, including memory impairments and more global cognitive deficits. Clinical-epidemiological evidence suggests that neuropsychiatric symptoms precede the onset of cognitive symptoms both in humans with early and late onset AD. The behavioural profile promoted by the AD pathology is believed to associate with degeneration of the serotonergic system. Using the APP_swe/PS1_δE9 model of AD-like pathology starting with 9 months old mice, we characterised long term non-cognitive behavioural changes measured at 9, 12, 15, and 18 months of age and applied principal component analysis on data obtained from open field, elevated plus maze, and social interaction tests. Long-term treatment with the selective serotonin reuptake inhibitor (SSRI) paroxetine was applied to assess the role of 5-HT on the behavioural profile; duration of treatment was 9 months, initiated when mice were 9 months of age. Treatment with paroxetine delays the decline in locomotion, in exploration and risk assessment behaviour, found in the APP/PS1 mice. APP/PS1 mice also exhibit low social activity and less aggressiveness, both of which are not affected by treatment with paroxetine. The APP/PS1 behavioural phenotype, demonstrated in this study, only begins to manifest itself from 12 months of age. Our results indicate that treatment with SSRI might ameliorate some of the behavioural deficits found in aged APP/PS1 mice.

A Comprehensive Behavioral Test Battery to Assess Learning and Memory in 129S6/Tg2576 Mice

Transgenic Tg2576 mice overexpressing human amyloid precursor protein (hAPP) are a widely used Alzheimer's disease (AD) mouse model to evaluate treatment effects on amyloid beta (Aβ) pathology and cognition. Tg2576 mice on a B6;SJL background strain carry a recessive rd1 mutation that leads to early retinal degeneration and visual impairment in homozygous carriers. This can impair performance in behavioral tests that rely on visual cues, and thus, affect study results. Therefore, B6;SJL/Tg2576 mice were systematically backcrossed with 129S6/SvEvTac mice resulting in 129S6/Tg2576 mice that lack the rd1 mutation. 129S6/Tg2576 mice do not develop retinal degeneration but still show Aβ accumulation in the brain that is comparable to the original B6;SJL/Tg2576 mouse. However, comprehensive studies on cognitive decline in 129S6/Tg2576 mice are limited. In this study, we used two dementia mouse models on a 129S6 background--scopolamine-treated 129S6/SvEvTac mice (3-5 month-old) and transgenic 129S6/Tg2576 mice (11-13 month-old)-to establish a behavioral test battery for assessing learning and memory. The test battery consisted of five tests to evaluate different aspects of cognitive impairment: a Y-Maze forced alternation task, a novel object recognition test, the Morris water maze, the radial arm water maze, and a Y-maze spontaneous alternation task. We first established this behavioral test battery with the scopolamine-induced dementia model using 129S6/SvEvTac mice and then evaluated 129S6/Tg2576 mice using the same testing protocol. Both models showed distinctive patterns of cognitive impairment. Together, the non-invasive behavioral test battery presented here allows detecting cognitive impairment in scopolamine-treated 129S6/SvEvTac mice and in transgenic 129S6/Tg2576 mice. Due to the modular nature of this test battery, more behavioral tests, e.g. invasive assays to gain additional cognitive information, can easily be added.

Biology and Diseases of Mice

Today’s laboratory mouse, Mus musculus, has its origins as the ‘house mouse’ of North America and Europe. Beginning with mice bred by mouse fanciers, laboratory stocks (outbred) derived from M. musculus musculus from eastern Europe and M. m. domesticus from western Europe were developed into inbred strains. Since the mid-1980s, additional strains have been developed from Asian mice (M. m. castaneus from Thailand and M. m. molossinus from Japan) and from M. spretus which originated from the western Mediterranean region.

Histone deacetylase 6 inhibition improves memory and reduces total tau levels in a mouse model of tau deposition

Introduction

Tau pathology is associated with a number of age-related neurodegenerative disorders. Few treatments have been demonstrated to diminish the impact of tau pathology in mouse models and none are yet effective in humans. Histone deacetylase 6 (HDAC6) is an enzyme that removes acetyl groups from cytoplasmic proteins, rather than nuclear histones. Its substrates include tubulin, heat shock protein 90 and cortactin. Tubastatin A is a selective inhibitor of HDAC6. Modification of tau pathology by specific inhibition of HDAC6 presents a potential therapeutic approach in tauopathy.

Methods

We treated rTg4510 mouse models of tau deposition and non-transgenic mice with tubastatin (25 mg/kg) or saline (0.9%) from 5 to 7 months of age. Cognitive behavior analysis, histology and biochemical analysis were applied to access the effect of tubastatin on memory, tau pathology and neurodegeneration (hippocampal volume).

Results

We present data showing that tubastatin restored memory function in rTg4510 mice and reversed a hyperactivity phenotype. We further found that tubastatin reduced the levels of total tau, both histologically and by western analysis. Reduction in total tau levels was positively correlated with memory improvement in these mice. However, there was no impact on phosphorylated forms of tau, either by histology or western analysis, nor was there an impact on silver positive inclusions histologically.

Conclusion

Potential mechanisms by which HDAC6 inhibitors might benefit the rTg4510 mouse include stabilization of microtubules secondary to increased tubulin acetylation, increased degradation of tau secondary to increased acetylation of HSP90 or both. These data support the use of HDAC6 inhibitors as potential therapeutic agents against tau pathology.

Optimization of apparatus design and behavioral measures for the assessment of visuo-spatial learning and memory of mice on the Barnes maze

We have previously shown that apparatus design can affect visual-spatial cue use and memory performance of mice on the Barnes maze. The present experiment extends these findings by determining the optimal behavioral measures and test procedure for analyzing visuo-spatial learning and memory in three different Barnes maze designs. Male and female C57BL/6J mice were trained with a stable or random escape hole location and the sensitivities (statistical power) of four commonly used measures of learning and three measures of memory to detect differences between these training procedures were compared on each maze design. A maze design with a large diameter and no wall was optimal, because mice showed a reliable use of extra-maze visual cues, visuo-spatial search strategies, and spatial memory. A maze design with a small diameter, surrounding wall, and intra-maze visual cues was the least sensitive for determining visuo-spatial learning and memory, because mice showed little evidence of extra-maze cue use. Errors, distance traveled, and hole deviation scores were more sensitive measures of learning than latency to find the escape hole. Measures based on locating the escape hole (primary measures) were more sensitive than measures based on entering the escape hole (total measures). Measures of memory had similar levels of sensitivity on each maze. This experiment demonstrates that both apparatus design and the behavioral measures used as indicators of learning and memory can influence the ability of the Barnes maze to detect visuo-spatial learning and memory impairments in mice.

Neurodegeneration of the retina in mouse models of Alzheimer's disease: what can we learn from the retina?

Alzheimer's disease (AD) is an age-related progressive neurodegenerative disease commonly found among elderly. In addition to cognitive and behavioral deficits, vision abnormalities are prevalent in AD patients. Recent studies investigating retinal changes in AD double-transgenic mice have shown altered processing of amyloid precursor protein and accumulation of β-amyloid peptides in neurons of retinal ganglion cell layer (RGCL) and inner nuclear layer (INL). Apoptotic cells were also detected in the RGCL. Thus, the pathophysiological changes of retinas in AD patients are possibly resembled by AD transgenic models. The retina is a simple model of the brain in the sense that some pathological changes and therapeutic strategies from the retina may be observed or applicable to the brain. Furthermore, it is also possible to advance our understanding of pathological mechanisms in other retinal degenerative diseases. Therefore, studying AD-related retinal degeneration is a promising way for the investigation on (1) AD pathologies and therapies that would eventually benefit the brain and (2) cellular mechanisms in other retinal degenerations such as glaucoma and age-related macular degeneration. This review will highlight the efforts on retinal degenerative research using AD transgenic mouse models.

Beta-secretase inhibitor GRL-8234 rescues age-related cognitive decline in APP transgenic mice

Alzheimer disease is intimately linked to an excess amount of amyloid-β (Aβ) in the brain. Thus, therapeutic inhibition of Aβ production is an attractive clinical approach to treat this disease. Here we provide the first direct experimental evidence that the treatment of Tg2576 transgenic mice with an inhibitor of β-secretase, GRL-8234, rescues the age-related cognitive decline. We demonstrated that the injected GRL-8234 effectively enters the brain and rapidly decreases soluble Aβ in the brain of Tg2576 mice. The rescue of cognition, which was observed only after long-term inhibitor treatment ranging from 5 to 7.5 mo, was associated with a decrease of brain amyloid-β plaque load. We also found no accumulation of amyloid-β precursor protein after several months of inhibitor treatment. These observations substantiate the idea that Aβ accumulation plays a major role in the cognitive decline of Tg2576 mice and support the concept of Aβ reduction therapy as a treatment of AD.

Visuo-spatial learning and memory deficits on the Barnes maze in the 16-month-old APPswe/PS1dE9 mouse model of Alzheimer's disease

The APPswe/PS1dE9 mouse is a double transgenic model of Alzheimer's disease, which harbors mutant mouse/human amyloid precursor protein (Swedish K594N/M595L) and presenilin-1 genes (PS1-dE9). These mice develop beta-amyloid plaques and exhibit visuo-spatial learning and memory impairment in the Morris water maze (MWM) at 8-12 and 16-18 months of age. To extend these findings, we tested visuo-spatial learning and memory of male and female APPswe/PS1dE9 mice at 16 months of age on the Barnes maze. APPswe/PS1dE9 mice showed impaired acquisition learning using measures of latency, distance traveled, errors and hole deviation scores, and were less likely to use the spatial search strategy to locate the escape hole than wild-type mice. APPswe/PS1dE9 mice also showed a deficit in memory in probe tests on the Barnes maze relative to wild-type mice. Learning and memory deficits, however, were not found during reversal training and reversal probe tests. Sex differences were observed, as male APPswe/PS1dE9 mice had smaller reversal effects than male wild-type mice, but females of each genotype did not differ. Overall, these results replicate previous findings using the MWM, and indicate that APPswe/PS1dE9 mice have impaired visuo-spatial learning and memory at 16 months of age.

Chronic administration of R-flurbiprofen attenuates learning impairments in transgenic amyloid precursor protein mice

Background

Long-term use of non-steroidal anti-inflammatory drugs (NSAIDs) is associated with a reduced incidence of Alzheimer's disease (AD). We and others have shown that certain NSAIDs reduce secretion of Aβ42 in cell culture and animal models, and that the effect of NSAIDs on Aβ42 is independent of the inhibition of cyclooxygenase by these compounds. Since Aβ42 is hypothesized to be the initiating pathologic molecule in AD, the ability of these compounds to lower Aβ42 selectively may be associated with their protective effect. We have previously identified R-flurbiprofen (tarenflurbil) as a selective Aβ42 lowering agent with greatly reduced cyclooxygenase activity that shows promise for testing this hypothesis. In this study we report the effect of chronic R-flurbiprofen treatment on cognition and Aβ loads in Tg2576 APP mice.

Results

A four-month preventative treatment regimen with R-flurbiprofen (10 mg/kg/day) was administered to young Tg2576 mice prior to robust plaque or Aβ pathology. This treatment regimen improved spatial learning as assessed by the Morris water maze, indicated by an increased spatial bias during the third probe trial and an increased utilization of a place strategy to solve the water maze. These results are consistent with an improvement in hippocampal- and medial temporal lobe-dependent memory function. A modest, though not statistically significant, reduction in formic acid-soluble levels of Aβ was also observed. To determine if R-flurbiprofen could reverse cognitive deficits in Tg2576 mice where plaque pathology was already robust, a two-week therapeutic treatment was given to older Tg2576 mice with the same dose of R-flurbiprofen. This approach resulted in a significant decrease in Aβ plaque burden but no significant improvement in spatial learning.

Conclusion

We have found that chronic administration of R-flurbiprofen is able to attenuate spatial learning deficits if given prior to plaque deposition in Tg2576 mice. Given its ability to selectively target Aβ42 production and improve cognitive impairments in transgenic APP mice, as well as promising data from a phase 2 human clinical trial, future studies are needed to investigate the utility of R-flurbiprofen as an AD therapeutic and its possible mechanisms of action.

Behavioral consequences of ovarian atrophy and estrogen replacement in the APPswe mouse

Cognitive performance was evaluated in a longitudinal study of APPswe2576 transgenic mice (APP) and a wildtype (WT) comparison group. Subgroups of the APP mice were treated with the ovarian toxicant 4-vinylcyclo-hexene diepoxide (VCD) at 60-75 days of age to induce ovarian atrophy and/or given estrogen (estradiol, 4 microg/day) continuously by pellet from 76 days of age. APP mice had a generally poorer radial maze performance than WT at 4.5, 7.5, 10.5 and 15 months of age. In separate tests, APP mice had a slight motor impairment, higher incidence of homecage stereotypy, hyperactivity in an open field and reduced object exploration relative to the WT group. Ovarian atrophy led to better maze performance at 7.5 months. The effect of estrogen on maze performance with aging could not be effectively evaluated due to poor survival (30%) of these mice. No effects of ovarian atrophy or estrogen treatment were identified for amyloid-beta accumulation or plaque formation at 15 months. Long-term longitudinal studies in animal models are needed to explore the consequences of menopause and hormone replacement on Alzheimer's disease, but they are complicated by considerations of survival, pre-aging deficits, testing experience and selection of appropriate estrogen treatment levels.

The influence of visual ability on learning and memory performance in 13 strains of mice

We calculated visual ability in 13 strains of mice (129SI/Sv1mJ, A/J, AKR/J, BALB/cByJ, C3H/HeJ, C57BL/6J, CAST/EiJ, DBA/2J, FVB/NJ, MOLF/EiJ, SJL/J, SM/J, and SPRET/EiJ) on visual detection, pattern discrimination, and visual acuity and tested these and other mice of the same strains in a behavioral test battery that evaluated visuo-spatial learning and memory, conditioned odor preference, and motor learning. Strain differences in visual acuity accounted for a significant proportion of the variance between strains in measures of learning and memory in the Morris water maze. Strain differences in motor learning performance were not influenced by visual ability. Conditioned odor preference was enhanced in mice with visual defects. These results indicate that visual ability must be accounted for when testing for strain differences in learning and memory in mice because differences in performance in many tasks may be due to visual deficits rather than differences in higher order cognitive functions. These results have significant implications for the search for the neural and genetic basis of learning and memory in mice.

Plaques, tangles, and memory loss in mouse models of neurodegeneration

Within the past decade, our understanding of the pathogenic mechanisms in Alzheimer's disease (AD) has dramatically advanced because of the development of transgenic mouse models that recapitulate the key pathological and behavioral phenotypes of the disease. These mouse models have allowed investigators to test detailed questions about how pathology develops and to evaluate potential therapeutic approaches that could slow down the development of this disease. In this review, we discuss the status of transgenic mouse models and review the complex relationship between pathology and behavior in the development of neuropathological syndromes in AD.

Age-related changes in visual acuity, learning and memory in C57BL/6J and DBA/2J mice

The DBA/2J mouse is a model of age-related pigmentary glaucoma in humans. Visual detection, pattern discrimination and visual acuity were evaluated in DBA/2J, C57BL/6J, B6.mpc1d (a C57 congenic strain) and D2.mpc1b (a D2 congenic strain) mice at 6, 12, 18 and 24 months of age. Mice were also tested in the Morris Water Maze and olfactory discrimination learning task. At 6 months, DBA/2J and D2.mpc1b mice outperformed C57BL/6J and B6.mpc1d mice in the visual detection task and there were no strain differences in performance on the water maze. At 12, 18 and 24 months, C57BL/6J and B6.mpc1d mice outperformed DBA/2J and D2.mpc1b mice in the vision tasks and in the water maze. Strains did not differ in the olfactory learning task. Therefore, loss of visual function occurs between 6 and 12 months of age in DBA/2J mice. Strain differences in visual task performance accounted for a significant proportion of the variance in measures of learning and memory in the water maze at 12, 18 and 24 months of age.

Effects of the rd1 mutation and host strain on hippocampal learning in mice

Many of the inbred mouse strains commonly used in biomedical research are homozygous for the rd1 mutation of the Pde6b gene, which causes retinal degeneration. To dissociate the behavioural effects of rd1 homozygosity from those of the genetic background of the host strain in the most widely used paradigms for evaluating the cognitive abilities of mice, two rd1 homozygous strains (C3H/HeJ and CBA/J) were compared with two Pde6b wild-type strains, each possessing a genetic background identical (C3A.BLiA-Pde6b+/J) or very similar (CBA/CaJ) to that of its rd1 homozygous relative. In the fear conditioning procedure, the presence of the rd1 mutation had no effect on performance at any stage, as the superior contextual learning of the CBA/J and CBA/CaJ strains could be explained by genetic background effects alone. In the Morris water maze, only the Pde6b wild-type C3A.BLiA-Pde6b+/J and CBA/CaJ strains were able to demonstrate spatial learning. The study thus demonstrates how retinal degeneration and genetic background have different effects in these two tests of hippocampus-dependent learning and memory.

Episodic-like memory deficits in the APPswe/PS1dE9 mouse model of Alzheimer's disease: relationships to beta-amyloid deposition and neurotransmitter abnormalities

Transgenic mice made by crossing animals expressing mutant amyloid precursor protein (APPswe) to mutant presenilin 1 (PS1dE9) allow for incremental increases in Abeta42 production and provide a model of Alzheimer-type amyloidosis. Here, we examine cognition in 6- and 18-month old transgenic mice expressing APPswe and PS1dE9, alone and in combination. Spatial reference memory was assessed in a standard Morris Water Maze task followed by assessment of episodic-like memory in Repeated Reversal and Radial Water maze tasks. We then used factor analysis to relate changes in performance in these tasks with cholinergic markers, somatostatin levels, and amyloid burden. At 6 months of age, APPswe/PS1dE9 double-transgenic mice showed visible plaque deposition; however, all genotypes, including double-transgenic mice, were indistinguishable from nontransgenic animals in all cognitive measures. In the 18-month-old cohorts, amyloid burdens were much higher in APPswe/PS1dE9 mice with statistically significant but mild decreases in cholinergic markers (cortex and hippocampus) and somatostatin levels (cortex). APPswe/PS1dE9 mice performed all cognitive tasks less well than mice from all other genotypes. Factor and correlation analyses defined the strongest correlation as between deficits in episodic-like memory tasks and total Abeta loads in the brain. Collectively, we find that, in the APPswe/PS1dE9 mouse model, some form of Abeta associated with amyloid deposition can disrupt cognitive circuits when the cholinergic and somatostatinergic systems remain relatively intact; and that episodic-like memory seems to be more sensitive to the toxic effects of Abeta.