RESUMO
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'.
Assuntos
Quirópteros , Sinais (Psicologia) , Ficus , Frutas , Memória Espacial , Animais , Quirópteros/fisiologia , Memória Espacial/fisiologia , Ficus/fisiologia , Comportamento Social , Comportamento Alimentar , Odorantes/análiseRESUMO
Prior research has used innovative paradigms to show that some non-human animal species demonstrate behavioural choices (i.e. foraging for a food item at a specific location, and at a time that guarantees it has not yet decayed), reflecting episodic-like or 'WWW' memory (memory for 'what' happened, 'where' and 'when'). These results raised the question of whether similar approaches could be used to examine memory in young children in order to reduce verbal demands. The present research examines the extent to which children's WWW memory aligns with memory-based choices in 3- to 5-year-olds (n = 95; study 1) and in 7- to 11-year-olds and adults (n = 168; study 2). Results indicate that preschoolers' struggle with choice-based tasks probably reflects difficulty integrating their WWW memory with an understanding that certain items decay over time. Moreover, a convergence between verbal recall measures and choice-based measures is observable in 7-year-olds and beyond, reflecting a stronger integration of memory signals, understanding of state transformation, and decision-making. This article is part of the theme issue 'Elements of episodic memory: lessons from 40 years of research'.
Assuntos
Tomada de Decisões , Criança , Humanos , Pré-Escolar , Masculino , Feminino , Adulto , Memória Espacial , Comportamento de Escolha , Rememoração Mental/fisiologiaRESUMO
Here, we show that during continuous navigation in a dynamic external environment, mice are capable of developing a foraging strategy based exclusively on changing distal (allothetic) information and that this process may involve two alternative components of the spatial memory circuit: the hippocampus and retrosplenial cortex. To this end, we designed a novel custom apparatus and implemented a behavioral protocol based on the figure-8-maze paradigm with two goal locations associated with distinct contexts. We assessed whether mice are able to learn to retrieve a sequence of rewards guided exclusively by the changing context. We found out that training mice in the apparatus leads to change in strategy from the internal tendency to alternate into navigation based exclusively on visual information. This effect could be achieved using two different training protocols: prolonged alternation training, or a flexible protocol with unpredictable turn succession. Based on the c-FOS mapping we also provide evidence of opposing levels of engagement of hippocampus and retrosplenial cortex after training of mice in these two different regimens. This supports the hypothesis of the existence of parallel circuits guiding spatial navigation, one based on the well-described hippocampal representation, and another, RSC-dependent.
Assuntos
Hipocampo , Proteínas Proto-Oncogênicas c-fos , Navegação Espacial , Animais , Navegação Espacial/fisiologia , Camundongos , Hipocampo/fisiologia , Proteínas Proto-Oncogênicas c-fos/metabolismo , Masculino , Aprendizagem em Labirinto/fisiologia , Camundongos Endogâmicos C57BL , Memória Espacial/fisiologiaRESUMO
How the brain mentally sorts a series of items in a specific order within working memory (WM) remains largely unknown. We investigated mental sorting using high-throughput electrophysiological recordings in the frontal cortex of macaque monkeys, who memorized and sorted spatial sequences in forward or backward orders according to visual cues. We discovered that items at each ordinal rank in WM were encoded in separate rank-WM subspaces and then, depending on cues, were maintained or reordered between the subspaces, accompanied by two extra temporary subspaces in two operation steps. Furthermore, the cue activity served as an indexical signal to trigger sorting processes. Thus, we propose a complete conceptual framework, where the neural landscape transitions in frontal neural states underlie the symbolic system for mental programming of sequence WM.
Assuntos
Lobo Frontal , Memória de Curto Prazo , Neurônios , Memória Espacial , Animais , Masculino , Sinais (Psicologia) , Lobo Frontal/citologia , Lobo Frontal/fisiologia , Macaca mulatta , Memória de Curto Prazo/fisiologia , Memória Espacial/fisiologia , Neurônios/fisiologiaRESUMO
Cognitive abilities are hypothesized to affect survival and life span in nonhuman animals. However, most tests of this hypothesis have relied on interspecific comparisons of indirect measures of cognitive ability, such as brain size. We present direct evidence that individual variation in cognitive abilities is associated with differences in life span in a wild food caching bird. We measured the spatial cognitive abilities and tracked the life span of 227 mountain chickadees (Poecile gambeli) in their natural environment and found that individuals with better spatial learning and memory abilities involved in food caching lived longer. These results confirm that enhanced cognitive abilities can be associated with longer life in wild animals and that selection on cognitive abilities can lead to increased life span.
Assuntos
Cognição , Comportamento Alimentar , Longevidade , Aves Canoras , Aprendizagem Espacial , Memória Espacial , Animais , Masculino , Memória , Aves Canoras/fisiologiaRESUMO
Most research on visual search has used simple tasks presented on a computer screen. However, in natural situations visual search almost always involves eye, head, and body movements in a three-dimensional (3D) environment. The different constraints imposed by these two types of search tasks might explain some of the discrepancies in our understanding concerning the use of memory resources and the role of contextual objects during search. To explore this issue, we analyzed a visual search task performed in an immersive virtual reality apartment. Participants searched for a series of geometric 3D objects while eye movements and head coordinates were recorded. Participants explored the apartment to locate target objects whose location and visibility were manipulated. For objects with reliable locations, we found that repeated searches led to a decrease in search time and number of fixations and to a reduction of errors. Searching for those objects that had been visible in previous trials but were only tested at the end of the experiment was also easier than finding objects for the first time, indicating incidental learning of context. More importantly, we found that body movements showed changes that reflected memory for target location: trajectories were shorter and movement velocities were higher, but only for those objects that had been searched for multiple times. We conclude that memory of 3D space and target location is a critical component of visual search and also modifies movement kinematics. In natural search, memory is used to optimize movement control and reduce energetic costs.
Assuntos
Movimentos Oculares , Memória Espacial , Realidade Virtual , Humanos , Feminino , Masculino , Adulto Jovem , Adulto , Movimentos Oculares/fisiologia , Memória Espacial/fisiologia , Percepção Espacial/fisiologia , Movimentos da Cabeça/fisiologia , Estimulação Luminosa/métodos , Percepção Visual/fisiologia , Tempo de Reação/fisiologiaRESUMO
BACKGROUND: Beneficial effects of whole-body vibration (WBV) on brain and musculoskeletal health in mice have been demonstrated, but underlying mechanisms remain relatively unrevealed. WBV improves attention and memory performance in mice, putatively through stimulation of the cholinergic system. Here, we investigated the effects of WBV on the septo-hippocampal cholinergic system. METHODS: Young C57BL/6 mice (8 weeks old) were subjected to 10 min WBV/day (mechanical vibration: 30 Hz; ~0.1-µm peak-to-peak displacement), 5X/week for 5 weeks. In Experiment 1, choline acetyltransferase (ChAT)-immunoreactivity in the septum and hippocampus was analyzed either 2 or 24 h after the last WBV session. Pseudo-WBV-treated mice (same handling procedure as WBV, but no vibrations) served as controls. In Experiment 2, the longitudinal profile of ChAT-immunoreactivity was analyzed in the hippocampus after 1, 2, 3, 4, or 5 weeks of WBV. In addition, synaptophysin immunostaining was performed at either 2 and 5 weeks of WBV. Mice housed 1/cage during the entire experiment served as controls. The balance-beam test was used to monitor the functional impact of WBV. In Experiment 3, a Y-maze reference-memory test was performed after 5 weeks of WBV to obtain a functional cognitive outcome measure of WBV. Pseudo-WBV treated mice served as controls. RESULTS: In Experiment 1, ChAT-immunoreactivity was significantly enhanced after the last WBV session of the 5-week period. This was found in the septum, Cornu Ammonis 1 (CA1), CA3, and dentate gyrus, and was dependent on layer and time-point (2 or 24 h). Experiment 2 revealed that, ChAT-immunoreactivity was lower after 2 weeks of WBV, whereas it was significantly higher after 5 weeks (similar to in Experiment 1). Immunostaining for synaptophysin, a marker for synaptic density, was also significantly higher after 5 weeks of WBV, but not significantly lower after 2 weeks, as was ChAT. WBV-treated groups performed significantly better than did controls on the balance beam from week 3 onwards. Experiment 3 showed that WBV-treated mice had better spatial-reference memory performance in the Y-maze test than did pseudo-WBV controls. CONCLUSIONS: Our results indicate that WBV stimulates the septo-hippocampal cholinergic system in a gradual and dynamic way that may contribute to improved spatial-memory performance. This finding suggests that WBV, by upregulation of the septo-hippocampal cholinergic system, may be considered a valuable therapeutic strategy to enhance brain functions in aging, neurodegenerative, and other brain diseases.
Assuntos
Colina O-Acetiltransferase , Hipocampo , Camundongos Endogâmicos C57BL , Memória Espacial , Sinaptofisina , Vibração , Animais , Hipocampo/metabolismo , Sinaptofisina/metabolismo , Colina O-Acetiltransferase/metabolismo , Memória Espacial/fisiologia , Masculino , Camundongos , Aprendizagem em Labirinto/fisiologia , Comportamento Animal/fisiologiaRESUMO
Glutamate is involved in fundamental functions, including neuronal plasticity and memory. Astrocytes are integral elements involved in synaptic function, and the GLT-1 transporter possesses a critical role in glutamate uptake. Here, we study the role of GLT-1, specifically located in astrocytes, in the consolidation, expression, reconsolidation and persistence of spatial object recognition memory in rats. Administration of dihydrokainic acid (DHK), a selective GLT-1 inhibitor, into the dorsal hippocampus around a weak training which only induces short-term memory, promotes long-term memory formation. This promotion is prevented by hippocampal administration of protein-synthesis translation inhibitor, blockade of Activity-regulated cytoskeleton-associated protein (Arc) translation or Brain-Derived Neurotrophic Factor (BDNF) action, which are plasticity related proteins necessary for memory consolidation. However, DHK around a strong training, which induces long-term memory, does not affect memory consolidation. Administration of DHK before the test session impairs the expression of long-term memory, and this effect is dependent of Arc translation. Furthermore, DHK impairs reconsolidation if applied before a reactivation session, and this effect is independent of Arc translation. These findings reveal specific consequences on spatial memory stages developed under hippocampal GLT-1 blockade, shedding light on the intricate molecular mechanisms, governed in part for the action of glia.
Assuntos
Astrócitos , Fator Neurotrófico Derivado do Encéfalo , Proteínas do Citoesqueleto , Ácido Glutâmico , Hipocampo , Memória Espacial , Animais , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Hipocampo/fisiologia , Astrócitos/efeitos dos fármacos , Astrócitos/metabolismo , Memória Espacial/efeitos dos fármacos , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Masculino , Ratos , Proteínas do Citoesqueleto/metabolismo , Proteínas do Citoesqueleto/genética , Ácido Glutâmico/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Proteínas do Tecido Nervoso/antagonistas & inibidores , Proteínas do Tecido Nervoso/genética , Transportador 2 de Aminoácido Excitatório/metabolismo , Transportador 2 de Aminoácido Excitatório/antagonistas & inibidores , Ratos Wistar , Ácido Caínico/farmacologia , Ácido Caínico/análogos & derivados , Consolidação da Memória/efeitos dos fármacosRESUMO
The detrimental effects of high-intensity noise on the auditory system and emotional status, including the induction of anxiety, are well documented. Preclinical as well as epidemiological and clinical studies have solidly established differential responses between males and females to various stressful stimuli, including high-intensity white noise (HIWN). However, whether chronic exposure to noise affects cognitive functions and whether this effect is sex dependent has not been adequately addressed. In this study, we used two cognitive test paradigms, such as the Morris water maze (MWM) and the multi-branch maze (MBM), to test the effect of chronic HIWN on indices of spatial learning and memory in both male and female Wistar rats. Our findings indicate that daily (1 h) exposure to 100 dB of noise for 30 consecutive days induces different task-dependent responses in male versus female rats. For example, in the acquisition phase of MWM, female rats exposed to noise outperformed their male counterparts at twice the speed. Similarly, in the MBM test, noise-exposed female rats outperformed the male rats in reaching the nest box. It is clear from these studies that noise impairs cognitive functions twice as negatively in male rats as in female rats. Thus, sex-related differences in spatial learning and memory in response to HIWN must be taken into consideration when investigating the neurobiological components and/or treatment modalities.
Assuntos
Aprendizagem em Labirinto , Ruído , Ratos Wistar , Caracteres Sexuais , Memória Espacial , Animais , Masculino , Feminino , Ruído/efeitos adversos , Memória Espacial/fisiologia , Ratos , Aprendizagem em Labirinto/fisiologiaRESUMO
Alzheimer's disease (AD), the most common cause of dementia, leads to neurodegeneration and cognitive decline. We investigated the therapeutic effects of L-carnitine on cognitive performance and anxiety-like behavior in a rat model of AD induced by unilateral intracerebroventricular injection of ß-amyloid1-42 (Aß1-42). L-carnitine (100 mg/kg/day) was administered intraperitoneally for 28 consecutive days. Following this, the open-field test, novel object recognition test, elevated plus-maze test, Barnes maze test, and passive avoidance learning test were used to assess locomotor activity, recognition memory, anxiety-like behavior, spatial memory, and passive avoidance memory, respectively. Plasma and hippocampal oxidative stress markers, including total oxidant status (TOS) and total antioxidant capacity (TAC), were examined. In addition, histological investigations were performed in the dentate gyrus of the hippocampus using Congo red staining and hematoxylin and eosin staining. The injection of Aß1-42 resulted in cognitive deficits and increased anxiety-like behavior. These changes were associated with an imbalance of oxidants and antioxidants in plasma and the hippocampus. Also, neuronal death and Aß plaque accumulation were increased in the hippocampal dentate gyrus region. However, injection of L-carnitine improved recognition memory, spatial memory, and passive avoidance memory in AD rats. These findings provide evidence that L-carnitine may alleviate anxiety-like behavior and cognitive deficits induced by Aß1-42 through modulating oxidative-antioxidant status and preventing Aß plaque accumulation and neuronal death.
Assuntos
Doença de Alzheimer , Peptídeos beta-Amiloides , Ansiedade , Carnitina , Modelos Animais de Doenças , Transtornos da Memória , Estresse Oxidativo , Ratos Wistar , Animais , Doença de Alzheimer/tratamento farmacológico , Doença de Alzheimer/psicologia , Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Ansiedade/tratamento farmacológico , Masculino , Transtornos da Memória/tratamento farmacológico , Transtornos da Memória/prevenção & controle , Ratos , Carnitina/farmacologia , Carnitina/uso terapêutico , Estresse Oxidativo/efeitos dos fármacos , Comportamento Animal/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Fragmentos de Peptídeos , Fármacos Neuroprotetores/farmacologia , Fármacos Neuroprotetores/uso terapêutico , Aprendizagem da Esquiva/efeitos dos fármacos , Aprendizagem em Labirinto/efeitos dos fármacos , Antioxidantes/farmacologia , Antioxidantes/uso terapêutico , Memória Espacial/efeitos dos fármacosRESUMO
Pregnancy and motherhood can have long-term effects on cognition and brain aging in both humans and rodents. Estrogens are related to cognitive function and neuroplasticity. Estrogens can improve cognition in postmenopausal women, but the evidence is mixed, partly due to differences in age of initiation, type of menopause, dose, formulation and route of administration. Additionally, past pregnancy influences brain aging and cognition as a younger age of first pregnancy in humans is associated with poorer aging outcomes. However, few animal studies have examined specific features of pregnancy history or the possible mechanisms underlying these changes. We examined whether maternal age at first pregnancy and estradiol differentially affected hippocampal neuroplasticity, inflammation, spatial reference cognition, and immediate early gene activation in response to spatial memory retrieval in middle-age. Thirteen-month-old rats (who were nulliparous (never mothered) or previously primiparous (had a litter) at three or seven months) received daily injections of estradiol (or vehicle) for sixteen days and were tested on the Morris Water Maze. An older age of first pregnancy was associated with impaired spatial memory but improved performance on reversal training, and increased number of new neurons in the ventral hippocampus. Estradiol decreased activation of new neurons in the dorsal hippocampus, regardless of parity history. Estradiol also decreased the production of anti-inflammatory cytokines based on age of first pregnancy. This work suggests that estradiol affects neuroplasticity and neuroinflammation in middle age, and that age of first pregnancy can have long lasting effects on hippocampus structure and function.
Assuntos
Estradiol , Hipocampo , Plasticidade Neuronal , Memória Espacial , Animais , Feminino , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Plasticidade Neuronal/efeitos dos fármacos , Plasticidade Neuronal/fisiologia , Gravidez , Memória Espacial/efeitos dos fármacos , Memória Espacial/fisiologia , Estradiol/farmacologia , Ratos , Inflamação/metabolismo , Aprendizagem em Labirinto/efeitos dos fármacos , Aprendizagem em Labirinto/fisiologia , Envelhecimento/fisiologia , Paridade/fisiologiaRESUMO
Exercise provides a range of cognitive benefits, including improved memory performance. Previously, we demonstrated that 14 days of continuous voluntary wheel-running exercise enables learning in a hippocampus-dependent Object Location Memory (OLM) task under insufficient, subthreshold training conditions in adult mice. Whether similar exercise benefits can be obtained from consistent intermittent exercise as continuous exercise is unknown. Here, we examine whether intermittent exercise (the weekend warrior effect: 2 days of exercise a week for 7 weeks) displays similar or distinct cognitive benefits as previously examined with 14 days of continuous exercise. We find that both continuous and intermittent exercise parameters similarly enable hippocampus-dependent OLM compared to the 2-day exercise control group. Mice receiving intermittent exercise maintained cognitive benefits following a 7-day sedentary delay, whereas mice that underwent 14 continuous days of exercise showed diminished cognitive benefits as previously reported. Further, compared to continuous exercise, intermittent exercise mice exhibited persistently elevated levels of the genes Acvr1c and Bdnf which we know to be critically involved in hippocampus-dependent long-term memory in the dorsal hippocampus. Together findings suggest that consistent intermittent exercise persistently enables hippocampal-dependent long-term memory. Understanding the optimal parameters for persistent cognitive function and the mechanisms mediating persistent effects will aid in therapeutic pursuits investigating the mitigation of cognitive ailments.
Assuntos
Fator Neurotrófico Derivado do Encéfalo , Hipocampo , Camundongos Endogâmicos C57BL , Condicionamento Físico Animal , Animais , Condicionamento Físico Animal/fisiologia , Hipocampo/fisiologia , Masculino , Camundongos , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Cognição/fisiologia , Memória de Longo Prazo/fisiologia , Memória Espacial/fisiologiaRESUMO
Hepatic encephalopathy (HE) is a neuropsychiatric syndrome that can occur in people with acute or chronic liver disease. Here, we investigated the effects of menthol, a natural monoterpene, on HE induced by thioacetamide (TA) in male Wistar rats. The rats received 200 mg/kg of TA twice a week for four weeks and were administered 10 mg/kg of menthol intraperitoneally daily for the same period. The results showed that menthol treatment reduced oxidative stress and inflammation in the livers and hippocampi of the rats that received TA. It also lowered the levels of ammonium and liver enzymes AST, ALT, ALP, and GGT in the serum of these animals and prevented liver histopathological damage. In addition, the expression and activity of acetylcholinesterase in the hippocampus of HE model rats were decreased by menthol. Likewise, this monoterpene reduced the expression of TLR4, MyD88, and NF-κB in the hippocampus while increasing the expression of BDNF and α7-nACh receptor. Menthol also reduced neuronal death in the hippocampal cornu ammonis-1 and dentate gyrus regions and reduced astrocyte swelling, which led to improved learning and spatial memory in rats with HE. In conclusion, the study suggests that menthol may have strong protective effects on the liver and brain, making it a potential treatment for HE and neurodegenerative diseases.
Assuntos
Fator Neurotrófico Derivado do Encéfalo , Encefalopatia Hepática , Hipocampo , Mentol , Estresse Oxidativo , Ratos Wistar , Memória Espacial , Tioacetamida , Receptor 4 Toll-Like , Animais , Masculino , Estresse Oxidativo/efeitos dos fármacos , Encefalopatia Hepática/tratamento farmacológico , Encefalopatia Hepática/metabolismo , Encefalopatia Hepática/induzido quimicamente , Encefalopatia Hepática/prevenção & controle , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Ratos , Mentol/farmacologia , Memória Espacial/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Hipocampo/patologia , Receptor 4 Toll-Like/metabolismo , Fígado/efeitos dos fármacos , Fígado/metabolismo , Fígado/patologia , Inflamação/tratamento farmacológico , Inflamação/metabolismo , NF-kappa B/metabolismo , Fator 88 de Diferenciação Mieloide/metabolismo , Fármacos Neuroprotetores/farmacologia , Fármacos Neuroprotetores/uso terapêutico , Acetilcolinesterase/metabolismoRESUMO
Consumption of saturated fat-enriched diets during adolescence has been closely associated with the reduction of hippocampal synaptic plasticity and the impairment of cognitive function. Nevertheless, the effect of long-term intake of these foods has not yet been studied. In the present study, we have investigated the effect of a treatment, lasting for 40 weeks, with a diet enriched in saturated fat (SOLF) on i) spatial learning and memory, ii) hippocampal synaptic transmission and plasticity, and iii) hippocampal gene expression levels in aged male and female mice. Our findings reveal that SOLF has a detrimental impact on spatial memory and synaptic plasticity mechanisms, such as long-term potentiation (LTP), and downregulates Gria1 expression specifically in males. In females, SOLF downregulates the gene expression of Gria1/2/3 and Grin1/2A/2B glutamate receptor subunits as well as some proinflammatory interleukins. These findings highlight the importance of considering sex-specific factors when assessing the long-term effects of high-fat diets on cognition and brain plasticity.
Assuntos
Dieta Hiperlipídica , Hipocampo , Caracteres Sexuais , Animais , Masculino , Feminino , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Dieta Hiperlipídica/efeitos adversos , Camundongos , Camundongos Endogâmicos C57BL , Plasticidade Neuronal/efeitos dos fármacos , Plasticidade Neuronal/fisiologia , Aprendizagem Espacial/efeitos dos fármacos , Aprendizagem Espacial/fisiologia , Receptores de AMPA/metabolismo , Memória Espacial/efeitos dos fármacos , Memória Espacial/fisiologia , Memória/efeitos dos fármacos , Memória/fisiologia , Potenciação de Longa Duração/efeitos dos fármacos , Potenciação de Longa Duração/fisiologia , Receptores de N-Metil-D-Aspartato/metabolismo , Transmissão Sináptica/efeitos dos fármacos , Transmissão Sináptica/fisiologia , Gorduras na Dieta/farmacologiaRESUMO
TIAM Rac1-associated GEF 2 short-form protein (TIAM2S) is abundant in specific brain tissues, especially in the hippocampus, a brain region critical for processing and consolidation of spatial memory. However, how TIAM2S plasticizes the microstructure and circuits of the hippocampus to shape spatial memory as a neuroplastic regulator during aging remains to be determined. In this study, transgenic mice overexpressing human TIAM2S protein (TIAM2S-TG mice) were included, and interdisciplinary approaches, such as spatial memory tests and multiparametric magnetic resonance imaging sequences, were conducted to determine the role and the mechanism of TIAM2S in age-related spatial memory deficits. Despite no changes in their neural and glial markers and neuropathological hallmark expression of the hippocampus, behavioral tests showed that the TIAM2S-TG mice, and not wild-type (WT) mice, developed spatial memory impairment at 18 months old. The T2-weighted and diffusion tensor image analyses were performed to further study the possible role of TIAM2S overexpression in altering the hippocampal structure or neuronal circlets of the mice, increasing their vulnerability to developing spatial memory deficits during aging. The results revealed that the 12-month-old TIAM2S-TG mice had hippocampal dysplasticity, with larger volume, increased fiber numbers, and changed mean fractional anisotropy compared to those in the age-matched WT mice. The fiber tractography analysis exhibited significantly attenuated structural connectivity between the hippocampus and medial prefrontal cortex in the TIAM2S-TG mice. In conclusion, overexpression of TIAM2S, a detrimental factor affecting hippocampus plasticity, causes attenuation of the connectivity within hippocampus-mPFC circuits, leading to age-related spatial memory impairment.
Assuntos
Envelhecimento , Fatores de Troca do Nucleotídeo Guanina , Hipocampo , Transtornos da Memória , Camundongos Transgênicos , Córtex Pré-Frontal , Memória Espacial , Animais , Hipocampo/metabolismo , Hipocampo/patologia , Camundongos , Transtornos da Memória/metabolismo , Transtornos da Memória/genética , Memória Espacial/fisiologia , Fatores de Troca do Nucleotídeo Guanina/genética , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Córtex Pré-Frontal/metabolismo , Envelhecimento/metabolismo , Envelhecimento/fisiologia , Envelhecimento/genética , Humanos , MasculinoRESUMO
Chemotherapy-related cognitive impairments (CRCIs) encompass cognitive deficits in memory, attention, and executive function that arise during and following chemotherapy. CRCI symptoms are predominantly reported by female cancer patients but also occur in males. These impairments may involve reduced estradiol levels, which then increases vulnerability to the impact of tumors and chemotherapy on cognition. This study utilized the MMTV-PyVT mouse model of breast cancer to test the hypothesis that impaired ovarian function and associated estradiol levels play a critical role in CRCI susceptibility. Mice were either ovariectomized (OVX) or underwent sham surgery. The OVX group then received supplemental estradiol (E2) ad libitum in the drinking water to maintain physiological hormone levels. After tumor development, mice were trained in the Morris water maze to assess spatial memory, and subsequently, they received weekly injections of either saline or a combination of cyclophosphamide (CYP; 66.7â mg/kg, i.v.) and doxorubicin (DOX; 6.7â mg/kg, i.v.) for 4â weeks. Spatial memory was reassessed 10â d and then 35â d, after the final injections. Results demonstrated a significant disruption of normal ovarian cycling in sham-operated mice treated with CYP + DOX, as well as significant spatial memory impairments when compared with OVX mice supplemented with E2 This study suggests that chemotherapy-induced ovarian damage and the consequent drop in circulating estrogens significantly contribute to vulnerability to CRCIs, underscoring the importance of estradiol in mitigating CRCI risks.
Assuntos
Ciclofosfamida , Doxorrubicina , Estradiol , Transtornos da Memória , Ovariectomia , Memória Espacial , Animais , Ciclofosfamida/toxicidade , Feminino , Estradiol/farmacologia , Estradiol/administração & dosagem , Doxorrubicina/toxicidade , Transtornos da Memória/induzido quimicamente , Transtornos da Memória/prevenção & controle , Memória Espacial/efeitos dos fármacos , Camundongos Transgênicos , Camundongos , Modelos Animais de Doenças , Comprometimento Cognitivo Relacionado à Quimioterapia , Aprendizagem em Labirinto/efeitos dos fármacosRESUMO
Studies on the development of visuo-spatial working memory (VSWM) have focused almost exclusively on memory tasks in which children had no control over the content of the representations they memorized. In contrast, in everyday life children often select the items that they encode in memory. In the current study, we used two modified span tasks to explore the development of this aspect of memory, termed self-initiated (SI) VSWM, in children aged 7 to 10 years. In Experiment 1 participants memorized sequences of spatial locations, whereas in Experiment 2 participants memorized sequences of pictures of real-world objects and the spatial locations of the targets were irrelevant for task performance. In both experiments, participants either selected the targets they memorized themselves or memorized randomly selected targets that were provided to them. Previous studies in adults have shown that efficient processing in the SI condition in both tasks entails the construction of spatially structured representations. The results of the two experiments revealed that children constructed spatially structured representations with short paths between successive locations in the spatial sequences, fewer path crossings, and more linear shapes compared with the provided representations. Self-initiation benefited overall performance, especially in Experiment 1 where the memory task was more demanding. This study shows that 7- to 10-year-old children have access to the metacognitive knowledge on the spatial structure of VSWM and strategically impose structure during encoding to benefit memory performance. More generally, SI VSWM highlights an important aspect of behavior, demonstrating how children shape their environment to facilitate functioning.
Assuntos
Memória de Curto Prazo , Percepção Espacial , Humanos , Criança , Feminino , Masculino , Percepção Espacial/fisiologia , Desenvolvimento Infantil/fisiologia , Memória Espacial , Percepção Visual/fisiologiaRESUMO
Spatial locations can be encoded and maintained in working memory using different representations and strategies. Fine-grained representations provide detailed stimulus information, but are cognitively demanding and prone to inexactness. The uncertainty in fine-grained representations can be compensated by the use of coarse, but robust categorical representations. In this study, we employed an individual differences approach to identify brain activity correlates of the use of fine-grained and categorical representations in spatial working memory. We combined data from six functional magnetic resonance imaging studies, resulting in a sample of $155$ ($77$ women, $25 \pm 5$ years) healthy participants performing a spatial working memory task. Our results showed that individual differences in the use of spatial representations in working memory were associated with distinct patterns of brain activity. Higher precision of fine-grained representations was related to greater engagement of attentional and control brain systems throughout the task trial, and the stronger deactivation of the default network at the time of stimulus encoding. In contrast, the use of categorical representations was associated with lower default network activity during encoding and higher frontoparietal network activation during maintenance. These results may indicate a greater need for attentional resources and protection against interference for fine-grained compared with categorical representations.
Assuntos
Encéfalo , Individualidade , Imageamento por Ressonância Magnética , Memória de Curto Prazo , Memória Espacial , Humanos , Memória de Curto Prazo/fisiologia , Feminino , Masculino , Adulto , Encéfalo/fisiologia , Encéfalo/diagnóstico por imagem , Adulto Jovem , Memória Espacial/fisiologia , Rede de Modo Padrão/fisiologia , Rede de Modo Padrão/diagnóstico por imagem , Mapeamento Encefálico , Rede Nervosa/fisiologia , Rede Nervosa/diagnóstico por imagem , Atenção/fisiologiaRESUMO
How do we mentally represent the world out there? Psychology, philosophy and neuroscience have given two classical answers: as a living space where we act and perceive, dependent on our bodies; as an enduring physical space with its feature, independent of our bodily interactions. The first would be based on egocentric frames of reference anchored to the body, while the second on allocentric frames of reference centred on the environment itself or on objects. This raises some questions concerning how deep the reliance on the body and the environment is when using these reference frames, and whether they are affected differently by the duration of time and the scale (small or large) of space. To answer these questions, I have brought empirical evidence of the effect of motor interference, blindness, environmental characteristics and temporal factors on egocentric and allocentric spatial representational capacity. The results suggest that egocentric representations are deeply rooted in the body, with its sensory and motor properties, and are closely linked to acting now in small-scale or peripersonal space. Allocentric representations are more influenced by environmental than by bodily characteristics, by visual than by motor properties, and seem particularly related to large-scale or extrapersonal space. In line with neurophysiological evidence and a Kantian perspective, it appears that we are endowed with an internal spatial representation system ready to structure environmental information for our purposes. To what extent this system is innate and pervasive in cognition and what is its relationship to the neural 'positioning' substrate discovered by O'Keefe and colleagues requires further scientific investigation.
Assuntos
Meio Ambiente , Percepção Espacial , Memória Espacial , Humanos , Percepção Espacial/fisiologia , Memória Espacial/fisiologia , Feminino , Masculino , Adulto , Adulto Jovem , Imagem CorporalRESUMO
This study explores the under-researched domain of long-term stimulant treatment in children and adolescents diagnosed with attention deficit hyperactivity disorder (ADHD). The necessity for extended treatment duration, often accompanied by safety concerns and side effects leading to treatment discontinuation, underscores the significance of this investigation. Concurrently, comparative studies have revealed adverse impacts on vulnerable regions within the hippocampal formation, accompanied by behavioral perturbations. We employed computerized tests and virtual reality to assess spatial memory, pattern separation, and object recognition memory in a cohort of children diagnosed with ADHD receiving stimulant treatment. We compared their performance to a group of neurotypical peers. Our findings indicate that the ADHD group exhibited a lower performance in spatial memory, pattern separation, and object recognition memory than ND group. Intriguingly, a positive relationship emerged between the duration of stimulant treatment and performance in these variables. Notably, this improvement was not immediate to MPH treatment but becomes significant after 24 months of treatment. In contrast to previous comparative investigations, our study did not reveal a detrimental impact on spatial navigation, object recognition memory, or pattern separation, despite the known interplay of these cognitive processes with the hippocampal formation. These results shed new light on the nuanced effects of stimulant treatment in ADHD, underscoring the need for a more comprehensive understanding of long-term treatment outcomes.