Spatial memory obviates following behaviour in an information centre of wild fruit bats.

According to the information centre hypothesis (ICH), colonial species use social information in roosts to locate ephemeral resources. Validating the ICH necessitates showing that uninformed individuals follow informed ones to the new resource. However, following behaviour may not be essential when individuals have a good memory of the resources' locations. For instance, Egyptian fruit bats forage on spatially predictable trees, but some bear fruit at unpredictable times. These circumstances suggest an alternative ICH pathway in which bats learn when fruits emerge from social cues in the roost but then use spatial memory to locate them without following conspecifics. Here, using an unique field manipulation and high-frequency tracking data, we test for this alternative pathway: we introduced bats smeared with the fruit odour of the unpredictably fruiting Ficus sycomorus trees to the roost, when they bore no fruits, and then tracked the movement of conspecifics exposed to the manipulated social cue. As predicted, bats visited the F. sycomorus trees with significantly higher probabilities than during routine foraging trips (of >200 bats). Our results show how the integration of spatial memory and social cues leads to efficient resource tracking and highlight the value of using large movement datasets and field experiments in behavioural ecology. This article is part of the theme issue 'The spatial-social interface: a theoretical and empirical integration'.

Spatial memory and learning: investigating the role of dynamic visual acuity.

Introduction: The vestibular system's contribution to spatial learning and memory abilities may be clarified using the virtual Morris Water Maze Task (vMWMT). This is important because of the connections between the vestibular system and the hippocampus area. However, there is ongoing debate over the role of the vestibular system in developing spatial abilities. This study aimed to evaluate the relationship between Dynamic Visual Acuity (DVA) across three planes and spatial abilities. Methods: This cross-sectional study was conducted with 50 healthy adults aged 18 to 55 with normal stress levels and mental health and no neurological, audiological, or vestibular complaints. The Trail-Making Test (TMT) Forms A and B for the assessment of executive functions, the DVA test battery for the evaluation of visual motor functions, and the Virtual Morris Water Maze Test (vMWMT) for the assessment of spatial learning and spatial memory were performed. All participants also underwent the Benton Face Recognition Test (BFRT) and Digit Symbol Substitution Tests (DSST) to assess their relation with spatial memory. Results: DVA values in horizontal (H-DVA), vertical (V-DVA), and sagittal (S-DVA) planes ranged from (-0.26) to 0.36 logMAR, (-0.20) to 0.36 logMAR, and (-0.28) to 0.33 logMAR, respectively. The latency of three planes of DVA was affected by vMWMT (Horizontal, Vertical, and Sagittal; Estimate: 22.733, 18.787, 13.341, respectively p < 0.001). Moreover, a moderately significant correlation was also found, with a value of 0.571 between the Virtual MWM test and BFRT and a value of 0.539 between the DSST (p < 0.001). Conclusion: Spatial abilities in healthy adults were significantly influenced by dynamic visual functions across horizontal, vertical, and sagittal planes. These findings are expected to trigger essential discussions about the mechanisms that connect the vestibular-visual system to the hippocampus. The original vMWMT protocol is likely to serve as a model for future studies utilizing this technology.

Revisiting serotonin's role in spatial memory: A call for sensitive analytical approaches.

The serotonergic system is involved in various psychiatric and neurological conditions, with serotonergic drugs often used in treatment. These conditions frequently affect spatial memory, which can serve as a model of declarative memory due to well-known cellular components and advanced methods that track neural activity and behavior with high temporal resolution. However, most findings on serotonin's effects on spatial learning and memory come from studies lacking refined analytical techniques and modern approaches needed to uncover the underlying neuronal mechanisms. This In Focus review critically investigates available studies to identify areas for further exploration. It finds that well-established behavioral models could yield more insights with modern tracking and data analysis approaches, while the cellular aspects of spatial memory remain underexplored. The review highlights the complex role of serotonin in spatial memory, which holds the potential for better understanding and treating memory-related disorders.

Genetic patterning in hippocampus of rat undergoing impaired spatial memory induced by long-term heat stress.

The organism's normal physiological function is greatly impacted in a febrile environment, leading to the manifestation of pathological conditions including elevated body temperature, dehydration, gastric bleeding, and spermatogenic dysfunction. Numerous lines of evidence indicate that heat stress significantly impacts the brain's structure and function. Previous studies have demonstrated that both animals and humans experience cognitive impairment as a result of exposure to high temperatures. However, there is a lack of research on the effects of prolonged exposure to high-temperature environments on learning and memory function, as well as the underlying molecular regulatory mechanisms. In this study, we examined the impact of long-term heat stress exposure on spatial memory function in rats and conducted transcriptome sequencing analysis of rat hippocampal tissues to identify the crucial molecular targets affected by prolonged heat stress exposure. It was found that the long-term heat stress impaired rats' spatial memory function due to the pathological damages and apoptosis of hippocampal neurons at the CA3 region, which is accompanied with the decrease of growth hormone level in peripheral blood. RNA sequencing analysis revealed the signaling pathways related to positive regulation of external stimulation response and innate immune response were dramatically affected by heat stress. Among the verified differentially expressed genes, the knockdown of Arhgap36 in neuronal cell line HT22 significantly enhances the cell apoptosis, suggesting the impaired spatial memory induced by long-term heat stress may at least partially be mediated by the dysregulation of Arhgap36 in hippocampal neurons. The uncovered relationship between molecular changes in the hippocampus and behavioral alterations induced by long-term heat stress may offer valuable insights for the development of therapeutic targets and protective drugs to enhance memory function in heat-exposed individuals.

Image memorability influences memory for where the item was seen but not when.

Observers can determine whether they have previously seen hundreds of images with more than 80% accuracy. This "massive memory" for WHAT we have seen is accompanied by smaller but still massive memories for WHERE and WHEN the item was seen (spatial & temporal massive memory). Recent studies have shown that certain images are more easily remembered than others (higher "memorability"). Does memorability influence spatial massive memory and temporal massive memory? In two experiments, viewers saw 150 images presented twice in random order. These 300 images were sequentially presented at random locations in a 7 × 7 grid. If an image was categorized as old, observers clicked on the spot in the grid where they thought they had previously seen it. They also noted when they had seen it: Experiment 1-clicking on a timeline; Experiment 2-estimating the trial number when the item first appeared. Replicating prior work, data show that high-memorability images are remembered better than low-memorability images. Interestingly, in both experiments, spatial memory precision was correlated with image memorability, while temporal memory precision did not vary as a function of memorability. Apparently, properties that make images memorable help us remember WHERE but not WHEN those images were presented. The lack of correlation between memorability and temporal memory is, of course, a negative result and should be treated with caution.

Dopamine D1 receptors activation rescues hippocampal synaptic plasticity and cognitive impairments in the MK-801 neonatal schizophrenia model.

Schizophrenia is a disorder with a higher cognitive decline in early adulthood, causing impaired retention of episodic memories. However, the physiological and behavioral functions that underlie cognitive deficits with a potential mechanism to ameliorate and improve cognitive performance are unknown. In this study, we used the MK-801 neurodevelopmental schizophrenia-like model. Rats were divided into two groups: one received MK-801, and the other received saline for five consecutive days (7-11 postnatal days, PND). We evaluated synaptic plasticity late-LTP and spatial memory consolidation in early adolescence and young adulthood using extracellular field recordings in acute hippocampal slices and the Barnes maze task. Next, we examined D1 receptor (D1R) activation as a mechanism to ameliorate cognitive impairments. Our results suggest that MK-801 neonatal treatment induces impairment in late-LTP expression and deficits in spatial memory retrieval in early adolescence that is maintained until young adulthood. Furthermore, we found that activation of dopamine D1R ameliorates the impairments and promotes a robust expression of late-LTP and an improved performance in the Barnes maze task, suggesting a novel and potential therapeutic role in treating cognitive impairments in schizophrenia.

Neonatal Cannabidiol Exposure Impairs Spatial Memory and Disrupts Neuronal Dendritic Morphology in Young Adult Rats.

Introduction: Early life is a sensitive period for brain development. Perinatal exposure to cannabis is increasingly linked to disruption of neurodevelopment; however, research on the effects of cannabidiol (CBD) on the developing brain is scarce. In this study, we aim to study the developmental effects of neonatal CBD exposure on behavior and dendritic architecture in young adult rats. Materials and Methods: Male and female neonatal Sprague Dawley rats were treated with CBD (50 mg/kg) intraperitoneally on postnatal day (PND) 1, 3, and 5 and evaluated for behavioral and neuronal morphological changes during early adulthood. Rats were subjected to a series of behavioral tasks to evaluate long-term effects of neonatal CBD exposure, including the Barnes maze, open field, and elevated plus maze paradigms to assess spatial memory and anxiety-like behavior. Following behavioral evaluation, animals were sacrificed, and neuronal morphology of the cortex and hippocampus was assessed using Golgi-Cox (GC) staining. Results: Rats treated with CBD displayed a sexually dimorphic response in spatial memory, with CBD-treated females developing a deficit but not males. CBD did not elicit alterations in anxiety-like behavior in either sex. Neonatal CBD caused an overall decrease in dendritic length and spine density (apical and basal) in cortical and hippocampal neurons in both sexes. Sholl analysis also revealed a decrease in dendritic intersections in the cortex and hippocampus, indicating reduced dendritic arborization. Conclusions: This study provides evidence that neonatal CBD exposure perturbs normal brain development and leads to lasting alterations in spatial memory and neuronal dendrite morphology in early adulthood, with sex-dependent sensitivity.

Unreliable association between self-reported sense of direction and peripheral vestibular function.

BACKGROUND: Uni- or bilateral peripheralvestibular impairment causes objective spatial orientation deficits, which can be measured using pen-and-paper-tests or sensorimotor tasks (navigation or pointing). For patients' subjective orientation abilities, questionnaires are commonly used (e.g., Santa Barbara sense of direction scale [SBSODS]). However, the relationship between subjective assessment of spatial skills and objective vestibular function has only been scarcely investigated. METHODS: A total of 177 patients (mean age 57.86 ± 17.53 years, 90 females) who presented in our tertiary Center for Vertigo and Balance Disorders underwent neuro-otological examinations, including bithermal water calorics, video head impulse test (vHIT), and testing of the subjective visual vertical (SVV), and filled out the SBSODS (German version). Correlation analyses and linear multiple regression model analyses were performed between vestibular test results and self-assessment scores. Additionally, groupwise vestibular function for patients with low, average, and high self-report scores was analyzed. RESULTS: Forty-two patients fulfilled the diagnostic criteria for bilateral vestibulopathy, 93 for chronic unilateral vestibulopathy (68 unilateral caloric hypofunction and 25 isolated horizontal vestibulo-ocular reflex deficits), and 42 patients had normal vestibular test results. SBSODS scores showed clear sex differences with higher subjective skill levels in males (mean score males: 4.94 ± 0.99, females 4.40 ± 0.94; Student's t-test: t-3.78, p < .001***). No stable correlation between objective vestibular function and subjective sense of spatial orientation was found. A multiple linear regression model could not reliably explain the self-reported variance. The three patient groups with low, average, and high self-assessment-scores showed no significant differences of vestibular function. CONCLUSION: Self-reported assessment of spatial orientation does not robustly correlate with objective peripheral vestibular function. Therefore, other methods of measuring spatial skills in real-world and virtual environments are required to disclose orientation deficits due to vestibular hypofunction.

Photoperiod, food restriction and memory for objects and places in mice.

The suprachiasmatic nucleus (SCN) contains a population of cell-autonomous circadian oscillators essential for entrainment to daily light-dark (LD) cycles. Synchrony among SCN oscillators is modified by photoperiod and determines functional properties of SCN clock cycling, including its amplitude, phase angle of entrainment, and free running periodicity (τ). For many species, encoding of daylength in SCN output is critical for seasonal regulation of metabolism and reproduction. C57BL/6 mice do not show seasonality in these functions, yet do show photoperiodic modulation of SCN clock output. The significance of this for brain systems and functions downstream from the SCN in these species is largely unexplored. C57BL/6 mice housed in a long-day photoperiod have been reported to perform better on tests of object, spatial and fear memory compared to mice in a standard 12 h photoperiod. We previously reported that encoding of photoperiod in SCN output, evident in τ in constant dark (DD), can be blocked by limiting food access to a 4 h mealtime in the light period. To determine whether this might also block the effect of long days on memory, mice entrained to 18 h:6 h (L18) or 6 h:18 h (L6) LD cycles were tested for 24 h object memory (novel object preference, NOP) and spatial working memory (Y-maze spontaneous alternation, SA), at 4 times of day, first with food available ad libitum and then during weeks 5-8 of daytime restricted feeding. Photoperiod modified τ as expected, but did not affect performance on the NOP and SA tests, either before or during restricted feeding. NOP performance did improve in the restricted feeding condition in both photoperiods, eliminating a weak time of day effect evident with food available ad-libitum. These results highlight benefits of restricted feeding on cognitive function, and suggest a dose-response relationship between photoperiod and memory, with no benefits at daylengths up to 18 h.

Cacao Ameliorates Amyloid Beta-Induced Cognitive and Non-Cognitive Disturbances.

Background: Alzheimer's disease (AD) is a progressive neurological disorder characterized by a wide range of cognitive and non-cognitive impairments. The present study was designed to investigate the potential effects of cacao on cognitive and non-cognitive performance and to identify the role of oxidative stress in an AD animal model induced by unilateral intracerebroventricular (U-ICV) injection of amyloid beta1-42 (Aß1-42). Methods: Oral administration of cacao (0.5 g/kg/day) was performed for 60 consecutive days. Following 60 days, the open-field (OF) test, elevated plus-maze (EPM) test, novel object recognition (NOR) test, Barnes maze (BM) test, and Morris water maze (MWM) test were used to evaluate locomotor activity, anxiety-like behavior, recognition memory, and spatial memory, respectively. Total oxidant status (TOS) and total antioxidant capacity (TAC) in plasma were also examined. Furthermore, the number of healthy cells in the hippocampus's dentate gyrus (DG), CA1, and CA3 regions were identified using hematoxylin and eosin staining. Results: The results indicated that the injection of Aß1-42 in rats led to recognition memory and spatial memory impairments, as well as increased anxiety. This was accompanied by decreased total antioxidant capacity (TAC), increased total oxidative stress (TOS), and increased neuronal death. Conversely, cacao treatment in AD rats improved memory function, reduced anxiety, modulated oxidative stress balance, and decreased neuronal death. Conclusion: The findings suggest that cacao's ability to improve the balance between oxidants and antioxidants and prevent neuronal loss may be the mechanism underlying its beneficial effect against AD-related cognitive and non-cognitive impairments.