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Results for “Spatial memory”

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At least 397 records · Page 22Linked to original sources

PubMed2002

NMDA receptor antagonists sustain LTP and spatial memory: active processes mediate LTP decay.

Although long-term potentiation (LTP) is long-lasting, it is not permanent and decays within weeks after its induction. Little is known about the processes underlying this decay. Here we assessed the contribution of synaptic activity to LTP decay by determining the effect of the competitive NMDA receptor antagonist CPP on the decay of perforant path-dentate LTP. CPP blocked decay over a one-week period when administered daily following the induction of LTP, and blocked decay of the late, protein-synthesis-dependent phase of LTP when administered two days after LTP induction. CPP administered for a five-day period following spatial memory training enhanced subsequent memory retention. These data suggest that LTP is normally a persistent process that is actively reversed by NMDA receptor activation, and that both the early and late phases of LTP are dynamic processes regulated by NMDA receptors. These data also support the view that LTP is involved in maintaining spatial memory.

Animals↗

PubMed2006

Developmental exposure to environmental estrogens alters anxiety and spatial memory in female mice.

Humans and wildlife are exposed to numerous anthropogenic drugs and pollutants. Many of these compounds are hormonally active, and recent evidence suggests that the presence of these endocrine disruptors permanently alters normal development and physiology in a variety of vertebrate species. Here, we report on the effects of developmental exposure to two common estrogenic pollutants, bisphenol A and ethinyl estradiol on sexually dimorphic, non-reproductive behavior. Mice (Mus musculus domesticus) were exposed to environmentally relevant levels of these chemicals (2 and 200 microg/kg/day for bisphenol A and 5 microg/kg/day for ethinyl estradiol) throughout prenatal and early postnatal development. As adults, the animals were observed in a variety of tests measuring sexually dimorphic behaviors including short-term spatial memory (in a radial-arm maze and a Barnes maze) and anxiety (in an elevated-plus maze and a light/dark preference chamber). Developmental exposure to ethinyl estradiol was found to masculinize behavior in all of the assays used. Bisphenol A increased anxious behavior in a dose-dependent fashion but had no effect on spatial memory. These results indicate that non-reproductive, sexually dimorphic behavior is sensitive to endocrine disruption. In addition, these experiments suggest that both humans and wildlife are being exposed to levels of these endocrine disrupting compounds that are sufficient to disrupt the development of the nervous system and that may have permanent consequences on sexually dimorphic behaviors.

Analysis of Variance↗

PubMed1997

Yoga breathing through a particular nostril increases spatial memory scores without lateralized effects.

Uninostril breathing facilitates the performance on spatial and verbal cognitive tasks, said to be right and left brain functions, respectively. Since hemispheric memory functions are also known to be lateralized, the present study assessed the effects of uninostril breathing on the performance in verbal and spatial memory tests. School children (N = 108 whose ages ranged from 10 to 17 years) were randomly assigned to four groups. Each group practiced a specific yoga breathing technique: (i) right nostril breathing, (ii) left nostril breathing, (iii) alternate nostril breathing, or (iv) breath awareness without manipulation of nostrils. These techniques were practiced for 10 days. Verbal and spatial memory was assessed initially and after 10 days. An age-matched control group of 27 were similarly assessed. All 4 trained groups showed a significant increase in spatial test scores at retest, but the control group showed no change. Average increase in spatial memory scores for the trained groups was 84%. It appears yoga breathing increases spatial rather than verbal scores, without a lateralized effect.

Adolescent↗

PubMed1985

Spatial memory in rats: electroconvulsive shock selectively disrupts working memory but spares reference memory.

In two experiments rats were trained until they displayed highly accurate spatial memories when a 4-h delay was imposed between the to-be-remembered event (TBRE) and the retention test in a 12-arm radial maze. If the procedure tested only working memory (WM) electronvulsive shock (ECS) 2 h after the TBRE produced amnesia but ECS immediately after the TBRE was ineffective. If the testing procedure also involved a reference memory (RM) component, ECS degraded WM regardless of whether it was given 0 or 2 h after the TBRE. RM was not affected. With either training procedure administering ECS 2 h before the TBRE was ineffective. Thus, in the radial maze truly old spatial RM was immune to disruption by ECS while more recent WM was vulnerable. Possible explanations of the data are presented.

Animals↗

PubMed1997

The effect of the loss of molar teeth on spatial memory and acetylcholine release from the parietal cortex in aged rats.

It has been demonstrated that a loss of teeth is a troublesome problem among age-related pathological phenomena of the oral cavity, which influences the entire body, due to the impairment of mastication. The present studies investigated the abilities of learning and memory and acetylcholine (ACh) release in the parietal cortex in aged rats without molar teeth (hereafter referred to as 'teethless'). After the molar teeth of rats were extracted, the rats were fed with powdered food for 135 weeks. Although the performance in the radial arm maze was progressively acquired by daily training, an increase in the number of errors and a decrease in the initial correct responses were observed in the teethless aged rats compared to the control aged rats, indicating impaired acquisition of spatial memory in the teethless aged rats. The basal level of extracellular ACh in the parietal cortex was not different between the teethless aged rats and the control aged rats. However, the extracellular ACh level of the teethless aged rats under high-concentration of K+ and atropine sulfate stimulation was significantly low compared to that of the control aged rats. These results suggest that the impairment of spatial memory in the teethless aged rats may be due to the functional deterioration of the cholinergic neuronal system induced by tooth loss and that there is a possibility that the loss of teeth may be one of the risk factors for senile dementia.

Acetylcholine↗

PubMed2006

Cerebral ischemia combined with beta-amyloid impairs spatial memory in the eight-arm radial maze task in rats.

beta-Amyloid (Abeta), a major component of senile plaques in Alzheimer's disease, has been implicated in neuronal cell death, a characteristic feature of this condition. In our previous experiments using primary cultures of hippocampal neurons, Abeta treatment induced neuronal cell death, displaying morphological characteristics of apoptosis that was significantly enhanced by hypoxia. Based on these results, we developed a simple in vivo rat model of Alzheimer's disease using cerebral ischemia, instead of hypoxia, combined with continuous intracerebroventricular administration of Abeta. The combination of cerebral ischemia and Abeta administration, but not either treatment alone, significantly impaired spatial memory in an eight-arm radial maze. A microdialysis study showed that spontaneous release of acetylcholine (ACh) from the dorsal hippocampus had a tendency to decrease in response to Abeta treatment alone or the combination of ischemia and Abeta. High K(+)-evoked increase in ACh release had a tendency to be inhibited by either ischemia or Abeta treatment alone and was significantly inhibited by the combination of both. Moreover, combination of ischemia and Abeta induced apoptosis of pyramidal neurons in the CA1 region of the hippocampus. Donepezil, a drug currently in clinical use for Alzheimer's disease, improved the impairment of spatial memory induced by cerebral ischemia combined with Abeta. These findings suggest that ischemia is an important factor facilitating the symptoms of Alzheimer's disease, and this model may be useful for developing new drugs for the treatment of Alzheimer's disease.

Amyloid beta-Peptides↗

PubMed2004

Orientational manoeuvres in the dark: dissociating allocentric and egocentric influences on spatial memory.

Subjects in a darkroom saw an array of five phosphorescent objects on a circular table and, after a short delay, indicated which object had been moved. During the delay the subject, the table or a phosphorescent landmark external to the array was moved (a rotation about the centre of the table) either alone or together. The subject then had to indicate which one of the five objects had been moved. A fully factorial design was used to detect the use of three types of representations of object location: (i) visual snapshots; (ii) egocentric representations updated by self-motion; and (iii) representations relative to the external cue. Improved performance was seen whenever the test array was oriented consistently with any of these stored representations. The influence of representations (i) and (ii) replicates previous work. The influence of representation (iii) is a novel finding which implies that allocentric representations play a role in spatial memory, even over short distances and times. The effect of the external cue was greater when initially experienced as stable. Females out-performed males except when the array was consistent with self-motion but not visual snapshots. These results enable a simple egocentric model of spatial memory to be extended to address large-scale navigation, including the effects of allocentric knowledge, landmark stability and gender.

Adult↗

PubMed1986

Kindling of the hippocampus induces spatial memory deficits in the rat.

Since kindling produces electrophysiological and morphological changes in the brain area stimulated, it may well affect behavioural functions dependent on the kindled area. Using an 8-arm maze, it was found that hippocampal kindling can induce specific memory deficits in spatial tasks. Reference (long-term) memory as well as working (short-term) memory were impaired. The largest impairment was observed during the period in which generalized convulsions occurred. Working memory but not reference memory impairment was reversible. Hippocampal kindling may be a useful experimental model for investigating behavioural deficits correlated with epileptogenesis.

Animals↗

PubMed2005

Preserved spatial memory after hippocampal lesions: effects of extensive experience in a complex environment.

Damage to the hippocampus typically impairs spatial learning and memory in animals, but humans with hippocampal lesions retain spatial memories of premorbidly familiar environments. We showed that, like humans, normal rats reared in a complex environment and then given hippocampal lesions retained allocentric spatial memory for that environment. These results, which ruled out dependency on single cues, landmarks or specific routes, suggest that extensive premorbid experience leads to spatial representations that are independent of the hippocampus.

Animals↗

PubMed2006

[Changes of NMDA receptor expression in rat hippocampal formation after establishment of spatial memory by different training modes].

There is no unambiguous report so far on whether short reinforcing training could establish stable spatial long-term memory and how the NMDA/NR1 expression in the hippocampal formation changes after establishment of short- and long-term memory. In the present study, three spatial memory training modes of Morris water maze were used: spatial long-term memory training mode (LT group), spatial short-term memory training mode (ST group) and short reinforcing training mode (SRT group). The characteristics of those memories established by different training modes were compared. The immunofluorescence histochemical staining technique was used to observe the changes of NMDA/NR1 expression in the hippocampal formation in the three groups. The results showed that, during Morris water maze training, no significant difference was found in the mean latency and the strategies to the target between the LT and SRT groups. The examination of the memories following different trainings indicated that the mean latency and the strategies to the target as well as the times crossing the target in LT group were not significantly different from those in SRT group, except that the mean time remaining in the platform quadrant in LT group was significantly longer than that in SRT group. In addition, no significant difference in the intensity of NMDA/NR1 immunoreactivity in CA1, CA3 and dentate gyrus of the hippocampal formation was observed between the control and ST groups or between LT and SRT groups. However, the intensity of NMDA/NR1 immunoreactivity in CA1 area and dentate gyrus in both LT and SRT groups was significantly increased as compared with that in ST or the control groups. These results suggest that the short reinforcing training mode can establish long-term spatial memory, which is almost the same as that established by the long-term training mode, and that the increase of NMDA/NR1 expression in CA1 area and dentate gyrus of the hippocampal formation may be one of the mechanisms of spatial long-term memory formation.

Animals↗

PubMed2002

Intrinsic frames of reference in spatial memory.

Three experiments investigated the frames of reference used in memory to represent the spatial structure of the environment. Participants learned the locations of objects in a room according to an intrinsic axis of the configuration; the axis was different from or the same as their viewing perspective. Judgments of relative direction using memory were most accurate for imagined headings parallel to the intrinsic axis, even when it differed from the viewing perspective, and there was no cost to learning the layout according to a nonegocentric axis. When the shape of the layout was bilaterally symmetric relative to the intrinsic axis of learning, novel headings orthogonal to that axis were retrieved more accurately than were other novel headings. These results indicate that spatial memories are defined with respect to intrinsic frames of reference, which are selected on the basis of egocentric experience and environmental cues.

Adult↗

PubMedDate not supplied

Involvement of BDNF receptor TrkB in spatial memory formation.

The N-methyl-D-aspartate (NMDA) receptors are involved in long-term potentiation (LTP), and are phosphorylated by several tyrosine kinases including a Src-family tyrosine kinase Fyn. Brain-derived neurotrophic factor (BDNF) is a neurotrophin, which also enhances hippocampal synaptic transmission and efficacy by increasing NMDA receptor activity. Here, we show that Fyn is a key molecule linking the BDNF receptor TrkB with NMDA receptors, which play an important role in spatial memory formation in a radial arm maze. Spatial learning induced phosphorylation of TrkB, Fyn, and NR2B, but not NR2A, in the hippocampus. Fyn was coimmunoprecipitated with TrkB and NR2B, and this association was increased in well-trained rats compared with control animals. Continuous intracerebroventricular infusion of PP2, a tyrosine kinase inhibitor, in rats delayed memory acquisition in the radial arm maze, but PP2-treated animals reached the same level of learning as the controls. The phosphorylation of Fyn and NR2B, but not TrkB, was diminished by PP2 treatment. Our findings suggest the importance of interaction between BDNF/TrkB signaling and NMDA receptors for spatial memory in the hippocampus.

Animals↗

PubMed1983

Opiate antagonists improve spatial memory.

Rats trained on an eight-arm radial maze were challenged by placing the maze in new spatial environments. Administration of opiate antagonists, either naloxone or diprenorphine, after exposure to the new environments significantly improved subsequent performance. The effect of naloxone on spatial memory was attenuated when drug administration occurred 2 hours after maze exposure.

Animals↗

PubMed1991

Evidence against a specific effect of cholinergic drugs on spatial memory in primates.

A scopolamine-like delay-dependent impairment in spatial delayed response performance in rhesus monkeys was induced by irrelevant interpolated activity or by using extended retention intervals. Physostigmine readily reversed the effects of scopolamine but had no effect on performance in young monkeys performing an irrelevant distractor task or in monkeys tested using extended retention intervals. Reducing stimulus control did not impair performance and did not alter the dose-response curve for induction of a deficit by scopolamine. Reducing the stimulus presentation time impaired performance across all retention intervals in a way which did not resemble the effect of scopolamine and which disappeared with practice. Our findings do not support the proposal that physostigmine interacts specifically with short-term spatial memory in primates.

Animals↗

PubMed2000

Fos expression in the rostral thalamic nuclei and associated cortical regions in response to different spatial memory tests.

Using the quantification of the Fos protein as an indicator of neuronal activation, we studied the involvement of the rostral thalamic nuclei and associated structures in different spatial memory tasks in two experiments. In both experiments, tasks were matched for sensorimotor factors but differed in their spatial and mnemonic demands. In Experiment 1, matched groups of rats either ran in a standard eight-arm radial maze or ran up and down just one arm of the maze while the number of runs and rewards were matched across pairs of rats. In Experiment 2, both groups were trained on the eight-arm radial maze but in different rooms. On the test day, one group was moved so that both groups now performed the same radial-maze task in the same room but for one group the extramaze cues were novel. There were significant increases in Fos in all three of the anterior thalamic nuclei (anterodorsal, anteroventral and anteromedial) as well as the adjacent nucleus reuniens and rostral reticular thalamic nucleus, in both the eight-arm versus one-arm condition (Experiment 1) and the novel room versus familiar room condition (Experiment 2). There were no significant differences in the mediodorsal thalamic nucleus in either experiment. The more spatially demanding task in each experiment also resulted in increased Fos expression in the subicular complex (postsubiculum, presubiculum and parasubiculum), as well as in the prelimbic cortex. Performing the standard radial-arm maze task also produced significant Fos increases in both rostral and caudal levels of the retrosplenial cortex when compared to rats running up and down a single arm in the same maze (Experiment 1); performing the task in a novel room did not, however, result in any further Fos increases in this region (Experiment 2). The specificity of the changes in levels of Fos was shown by a lack of any consistent difference in levels in six control sites.The present results reveal a group of anatomically related structures that work together in the intact rat brain during tasks that tax allocentric spatial working memory.

Animals↗

PubMed2004

Influence of hippocampectomy on habituation, exploratory behavior, and spatial memory in rats.

Two frequently cited functions of the hippocampus are mediation of spatial memories and habituation. The present investigation employed head-shake response (HSR) as the habituated behavior in intact and bilaterally hippocampectomized rats. This HSR appears to be minimally influenced by spatial cues. These rats were further tested on two behavioral paradigms that make use of spatial cues, namely open field object exploration, and the Morris water maze. The results indicate that hippocampectomized rats revealed habituation of the HSR, but not to objects within the open field. In agreement with previous reports, hippocampectomized rats were severely impaired both in acquiring and recalling the location of the submerged platform in the Morris water maze task. In a separate experiment independent groups of rats were trained on one of these three paradigms, and tissues were collected from hippocampal, prefrontal, and piriform cortices for the measurement of matrix metalloproteinases (MMPs) as markers of neural plasticity. There were significant MMP-9 elevations in the prefrontal and piriform cortices of rats tested using the object exploration task, in the prefrontal and hippocampal cortices of rats that solved the Morris water maze task, but minimal MMP changes in any tissues taken from HSR habituated rats. These results question the hypothesis that habituation is solely mediated by the hippocampus in favor of a process that utilizes different brain structures and degrees of neural plasticity dependent upon task requirements.

Animals↗

PubMed2006

Spatial memory: how egocentric and allocentric combine.

Recent experiments indicate the need for revision of a model of spatial memory consisting of viewpoint-specific representations, egocentric spatial updating and a geometric module for reorientation. Instead, it appears that both egocentric and allocentric representations exist in parallel, and combine to support behavior according to the task. Current research indicates complementary roles for these representations, with increasing dependence on allocentric representations with the amount of movement between presentation and retrieval, the number of objects remembered, and the size, familiarity and intrinsic structure of the environment. Identifying the neuronal mechanisms and functional roles of each type of representation, and of their interactions, promises to provide a framework for investigation of the organization of human memory more generally.

Cognition↗

PubMed2006

Deletion of the kinase domain from death-associated protein kinase enhances spatial memory in mice.

Death-associated protein kinase (DAPK) is a Ca2+/calmodulin-dependent serine/threonine kinase that is thought to mediate apoptosis. DAPK is highly expressed in hippocampal neurons which are essential elements for memory formation. To examine if DAPK is implicated in spatial learning and memory, both wild-type and DAPK-mutant mice were subjected to Morris water maze tests. DAPK-mutant mice were generated by deleting 74 amino acids from the catalytic kinase domain of DAPK, and were used to investigate roles of the DAPK kinase domain in regulating spatial memory. Both mutant and wild-type mice were able to learn the water maze tasks to locate a hidden escape platform. In the first probe test, mutant mice showed a more precise memory for platform position compared to wild-type mice. In the reversal training in which the platform was located opposite from the original position, DAPK-mutant mice exhibited superior spatial learning compared to wild-type mice. DAPK-mutant mice also showed a more precise memory than their wild-type littermates in the probe trial of reversal test. Thus, the present results revealed crucial implications of DAPK in regulating spatial memory in mice.

Animals↗