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At least 1,135 records · Page 63Linked to original sources
PubMed2006

Endocrine, liver-derived IGF-I is of importance for spatial learning and memory in old mice.

IGF-I is a neuroprotective hormone, and neurodegenerative disorders, including Alzheimer's disease, have been associated with decreased serum IGF-I concentration. In this study, IGF-I production was inactivated in the liver of adult mice (LI-IGF-I(-/-)), resulting in an approximately 80-85% reduction of circulating IGF-I concentrations. In young (6-month-old) mice there was no difference between the LI-IGF-I(-/-) and the control mice in spatial learning and memory as measured using the Morris water maze test. In old (aged 15 and 18 months) LI-IGF-I(-/-) mice, however, the acquisition of the spatial task was slower than in the controls. Furthermore, impaired spatial working as well as reference memory was observed in the old LI-IGF(-/-) mice. Histochemical analyses revealed an increase in dynorphin and enkephalin immunoreactivities but decreased mRNA levels in the hippocampus of old LI-IGF-I(-/-) mice. These mice also displayed astrocytosis and increased metabotropic glutamate receptor 7a-immunoreactivity. These neurochemical disturbances suggest synaptic dysfunction and early neurodegeneration in old LI-IGF-I(-/-) mice. The decline in serum IGF-I with increasing age may therefore be important for the age-related decline in memory function.

Aging↗
PubMed1981

Behavioral alterations caused by parasitic infection in case of latent toxoplasma infection.

In order to assess the effects of a latent Toxoplasma infection on behaviour and learning capacity, maze experiments with rats and mice were performed. The learning performance of rats and especially of mice was impaired, the memory of mice and their overall activity were reduced by infection. Theses results are supported by Hutchinson who also found that the activity of mice was reduced by Toxoplasma infection, and that they were less responsive to novel stimuli. These results indicate that Toxoplasma infection probably affects the animal's response to its environment, and the stimulation arising from it, and may even affect endogenous regulatory processes in the brain. Similar observations in humans suggest that an acquired Toxoplasma infection without giving rise to disease may have similar effects in man. These observations touch the general problem of the influence of parasitic infections on the CNS.

Animals↗
PubMedDate not supplied

[The effect of beta-casomorphin-7 on the level of food and defense motivations in different types of learning].

The effects of intraperitoneal administration of the heptapeptide beta-casomorphin-7 (beta-C-7) on learning were investigated in white rats using T-maze, active and passive avoidance tests. The substance injected in the dose of 5 mg/kg 5 min prior to training accelerated the acquisition of food-reinforced task increasing the number of correct trials in T-maze. The same injection in the dose of 1 mg/kg impaired the acquisition of avoidance tasks. The heptapeptide didn't influence food motivation and consolidation of memory trace. The data obtained support the idea that beta-C-7 attenuated manifestations of defensive motivation.

Acoustic Stimulation↗
PubMed2001

Clitoria ternatea (Linn) root extract treatment during growth spurt period enhances learning and memory in rats.

Neonatal rat pups (7 days old) were intubated with either 50 mg/kg body weight or 100 mg/kg body weight of aqueous root extract of Clitoria ternatea (CTR) for 30 days. These rats were then subjected to open field, two compartment passive avoidance and spatial learning (T-Maze) tests (i) immediately after the treatment and (ii) 30 days after the treatment, along with age matched normal and saline control rats. Results showed no change in open field behaviour, but showed improved retention and spatial learning performance at both time points of behavioural tests, indicating the memory enhancing property of CTR which implicates a permanent change in the brain of CTR treated rats.

Animals↗
PubMedDate not supplied

Age-dependent cognitive and behavioral deficits after kainic acid seizures.

The long-term behavioral and cognitive effects of seizures at different ages were studied using the kainic acid (KA) seizure model. Rats of postnatal (P) ages (in days) 5, 10, 20, 30, and 60 were administered KA intraperitoneally (i.p.), which induced status epilepticus for several hours, or an equivalent volume of saline. Occurrence of spontaneous recurrent seizures (SRS) was then monitored for 3 months by a closed-circuit videotaping system. Rats began behavioral testing on P80; a separate group of rats that received KA on P60 began testing on P120. Behavioral tests included the Morris water maze (visuospatial learning and memory), the open field test (response to a novel environment), and the handling test (emotionality). When tested on P80, KA-treated P5 and P10 rats had no demonstrable deficits on any test as compared with controls. KA-Treated P20 rats differed from controls only on the water maze spatial bias test. KA-Treated P30 rats had deficits in spatial bias, were more active in the open field, and were more aggressive when handled. KA-Treated P60 rats, whether tested on P80 or P120, had deficits in learning platform position and spatial bias in the water maze, were more active in the open field, and were more aggressive when handled. P60 rats with SRS performed poorer in water maze place learning and spatial bias testing, although the number of SRS did not correlate with overall task acquisition. Our findings suggest age-related behavioral and cognitive deficits after KA-induced seizures. Pubescents and adults had alterations in learning, memory, exploratory behavior, and response to handling, whereas younger animals had no obvious behavioral or cognitive deficits.

Age Factors↗
PubMed1989

Children's expressions of spatial knowledge.

Different expressions of spatial knowledge were examined by having groups of first-, fourth-, and sixth-grade children perform model construction, verbal description, and route reversal tasks after they learned the correct path through a pedestrian maze. Age-related improvement was found in the rate of learning the maze and in the accuracy of verbal descriptions, suggesting that maze learning may be verbally mediated. All children performed well in sequencing intersections in the model but performed poorly in choosing path options in the model. Route reversal after learning was accurate and equivalent across groups. Overall, results suggest that both general and task-specific skills are involved in different products of spatial knowledge.

Child↗
PubMedDate not supplied

The effects of lead toxication on learning in rats.

Impairment of learning resulting from lead poisoning has yet to be demonstrated in rats. The behavioral task used in previous studies to assess learning, however, may not have been sufficiently complex to serve as a discriminative index. The performance of rats injected with a lead acetate solution was compared to the performance of control rats in learning to run a complex maze. Though the learning acquisition rate was somewhat impaired in the lead-injected animals, the groups learned to complete the maze with equivalent success by the third training session. It was concluded that the study did not demonstrate convincing evidence of learning impairment in the lead-injected animals.

Animals↗
PubMed2004

Radiation-induced cognitive impairments are associated with changes in indicators of hippocampal neurogenesis.

During treatment of brain tumors, some head and neck tumors, and other diseases, like arteriovenous malformations, the normal brain is exposed to ionizing radiation. While high radiation doses can cause severe tissue destruction, lower doses can induce cognitive impairments without signs of overt tissue damage. The underlying pathogenesis of these impairments is not well understood but may involve the neural precursor cells in the dentate gyrus of the hippocampus. To assess the effects of radiation on cognitive function, 2-month-old mice received either sham treatment (controls) or localized X irradiation (10 Gy) to the hippocampus/cortex and were tested behaviorally 3 months later. Compared to controls, X-irradiated mice showed hippocampal-dependent spatial learning and memory impairments in the Barnes maze but not the Morris water maze. No nonspatial learning and memory impairments were detected. The cognitive impairments were associated with reductions in proliferating Ki-67-positive cells and Doublecortin-positive immature neurons in the subgranular zone (SGZ) of the dentate gyrus. This study shows significant cognitive impairments after a modest dose of radiation and demonstrates that the Barnes maze is particularly sensitive for the detection of radiation-induced cognitive deficits in young adult mice. The significant loss of proliferating SGZ cells and their progeny suggests a contributory role of reduced neurogenesis in the pathogenesis of radiation-induced cognitive impairments.

Animals↗
PubMed1991

Effects of ketamine and 1-glutamic acid diethyl ester on concept learning in rats.

The effects of ketamine, an NMDA receptor antagonist, and 1-glutamic acid diethyl ester (LGDE), a non-NMDA glutamate antagonist, were evaluated in the acquisition of concept learning in a water maze. In concept learning, the rats must locate an invisible platform whose location changes from day to day. In spatial learning (Morris task), the rats must locate an invisible (or visible) platform whose location does not change. Ketamine increased quadrant entries at 5, 10 and 20 mg/kg, and latencies at 10 and 20 mg/kg on the final two days of training on the concept task. At 5 mg/kg ketamine disrupted concept learning but not spatial learning or visuo-motor coordination as assessed by invisible and visible platform conditions of the Morris maze. Progressively higher doses of ketamine affected first the invisible condition and then the visible platform condition. On the other hand, LGDE did not affect the Morris task at any dose. However, there was no decrease in latencies over days in concept learning at the two highest doses (240 and 360 mg/kg) of LGDE. Thus LGDE appeared to slow down decision time in the concept task but not the spatial task in the absence of an effect on quadrant entries in any version. These results indicate that NMDA receptors are involved in spatial and concept learning. Non-NMDA receptors appear to be involved only in concept learning.

Animals↗
PubMed1980

Effects of administration of N-acetylneuraminic acid (NANA) on brain NANA content and behavior.

Rat pups were malnourished during the first 3 weeks after birth. Experimental rats were injected intraperitoneally with 1 mg N-acetylneuraminic acid (NANA) per 50 g body weight daily from 14 to 21 days postnatally. Control animals were similarly injected with 1 mg glucose per 50 g body weight. At 21 days of age, the rats were tested in an open field and their brains analyzed for protein, DNA, ganglioside NANA and glycoprotein NANA. The administration of NANA was associated with an increase in cerebral and cerebellar ganglioside and glycoprotein NANA concentrations. However, it had no effects on brain weight, cell size and number. There was also a reduction in the expected behavioral abnormalities secondary to malnutrition. At 21 days of age, similarly treated littermates of the experimental animals were weaned to a stock diet and tested in a Y maze at 6 months of age. Rats treated with NANA learned the maze quicker than controls and the previously noted changes in brain biochemistry were found to have persisted. Intraperitoneal injection of [14C]NANA into malnourished rats during the same period showed that it was readily incorporated into brain glycoproteins and gangliosides. The possibility that the brain concentration of NANA has an effect on behavior is discussed.

Animals↗
PubMed2003

An analysis of response, direction, and place learning in an open field and T maze.

Rats were trained to locate food in a response, direction, or place problem on an open field located at 2 positions. In Experiment 1, both the response and direction groups solved the problem. The place group failed to solve the task in approximately 300 trials. Experiment 2 demonstrated that rats need distinguishable start points to solve a place problem when neither a response nor a direction solution is available. Findings from Experiment 3 suggest that a combination of path traveled and distinct cues help to differentiate start points. Experiment 4 replicated the findings using a T maze. These results suggest "place" solutions are difficult for rats. The data are discussed with respect to conditional learning and modern spatial mapping theory.

Analysis of Variance↗
PubMed2006

Forebrain-specific knockout of B-raf kinase leads to deficits in hippocampal long-term potentiation, learning, and memory.

Raf kinases are downstream effectors of Ras and upstream activators of the MEK-ERK cascade. Ras and MEK-ERK signaling play roles in learning and memory (L&M) and neural plasticity, but the roles of Raf kinases in L&M and plasticity are unclear. Among Raf isoforms, B-raf is preferentially expressed in the brain. To determine whether B-raf has a role in synaptic plasticity and L&M, we used the Cre-LoxP gene targeting system to derive forebrain excitatory neuron B-raf knockout mice. This conditional knockout resulted in deficits in ERK activation and hippocampal long-term potentiation (LTP) and impairments in hippocampus-dependent L&M, including spatial learning and contextual discrimination. Despite the widespread expression of B-raf, this mutation did not disrupt other forms of L&M, such as cued fear conditioning and conditioned taste aversion. Our findings demonstrate that B-raf plays a role in hippocampal ERK activation, synaptic plasticity, and L&M.

Animals↗
PubMed1997

Magnetic resonance imaging and behavioral analysis of immature rats with kaolin-induced hydrocephalus: pre- and postshunting observations.

The motor and cognitive dysfunction associated with hydrocephalus remains a clinical problem in children. We hypothesized that young rats with hydrocephalus should exhibit similar dysfunction and that the dysfunction should be reversible by shunting. Hydrocephalus was induced in 3-week-old rats by injection of kaolin into the cisterna magna. Rats were assessed by T2-weighted images obtained with a 7-T magnetic resonance device and by repeated behavioral testing including ability to traverse a narrow beam and ability to find a hidden platform in a water pool. Some of the rats underwent a shunting procedure 1 or 4 weeks after kaolin injection. Magnetic resonance images were used to measure ventricle size. They clearly demonstrated increased signal in periventricular white matter, which corresponded to increased brain water content. A flow-void phenomenon was observed in the cerebral aqueduct. Ability to traverse the beam did not correlate with the degree of ventriculomegaly. Ability to swim to the hidden platform demonstrated a progressive impairment of learning function which may have been accentuated by motor disability. When rats were shunted after 1 week, the behavioral dysfunction was prevented. Late shunting after 4 weeks was associated with gradual recovery of the behavioral disability which was not complete after 4 weeks. We conclude that early shunting is superior to late shunting with regard to behavioral dysfunction. High-resolution MR imaging shows features in hydrocephalic rats similar to those found in hydrocephalic humans.

Animals↗
PubMed1995

Magnetic field effects on spatial discrimination and melatonin levels in mice.

Previous research has demonstrated a decrement in spatial discrimination learning following exposure to a .30 Tesla magnetic field. It had been suggested that those findings might be the result of an interaction between the magnetic field and physiological ferromagnetic material (magnetite). In the present study, mice were exposed for 100 min to a 2.0 Tesla field and both their left-right discrimination learning ability and serum melatonin levels were compared with a control group. Results indicated a significant interference with spatial discrimination learning following exposure, but no significant differences in serum melatonin levels. These findings appeared to rule out magnetically induced melatonin fatigue as an explanation of the decrement in spatial learning, as opposed to other possibilities such as magnetic effects on brain magnetite. However, additional controls are suggested for future research.

Animals↗
PubMed2005

Intermittent cold water swim stress increases immobility and interferes with escape performance in rat.

The behavioral consequences of intermittent, 5 s cold-water swims (15 degrees C) or confinement were assessed 24 h after stress in a 5 min forced swim test or an instrumental swim escape test (SET). The SET was conducted with temporal and instrumental parameters similar to the shock-motivated shuttle escape test. The tests detected significantly increased immobility in the forced swim test and increased latency to escape in the SET. These results extend previous findings with intermittent swim stress and provide evidence that intermittent swim stress produces behavioral deficits similar to other stress models. This new model may be a useful tool for exploring the physiological mechanisms underlying the stress response.

Analysis of Variance↗
PubMed2006

Analysis of spatial orientation strategies of male and female Wistar rats in a Morris water escape task.

In the present study we investigated spatial navigation in male and female Wistar rats in the Morris water escape task. Rats were subjected to procedures which required the use of a place (PLACE), cue (CUE) and egocentric (EGO) response to learn the task efficiently. In a first experiment rats were successively tested in the PLACE, CUE and EGO condition and in a second experiment the order of tasks was reversed. The first experiment showed that female rats swam longer distances and took more time to find the platform in the PLACE task. Further, the female rats spent less time near the previous platform position than the male rats during probe trial. No sex difference was found in the CUE and EGO task. In the second experiment, the female rats took longer to find the platform than the male rats in the EGO task. In the CUE and PLACE task no differences between the sexes was found during acquisition. However, the male rats spent more time near the previous platform position than the female rats during the probe trial of the PLACE task. On basis of present data it is concluded that the use of a PLACE-based strategy is better in male Wistar rats. CUE learning is not sex-dependent. The ability to use EGO strategies appears not to be different between male and female Wistar rats, but appears dependent on pre-exposure to the task.

Analysis of Variance↗
PubMed2004

Neural foundations of emerging route knowledge in complex spatial environments.

Behavioral evidence suggests that spatial knowledge derived from ground-level navigation can consist of both route and survey knowledge. Neuroimaging and lesion studies aiming to identify the neural structures responsible for topographical learning in humans have yielded partially inconsistent results, probably due to the lack of an effective behavioral parameter allowing for a reliable distinction between different representations. Therefore, we employed a novel virtual reality environment that provides accuracy and reaction time measures precisely indicating the emergence of route vs. survey knowledge. Functional magnetic resonance imaging (fMRI) was used to localize brain regions involved in the acquisition of pure route knowledge in the form of associations between consecutive landmark views and the direction of intermediate movements. Participants were scanned during repeated encoding of the complex environment from a first-person, ground-level perspective. Behavioral data revealed emerging route knowledge in 11 out of 14 subjects. Overall comparisons between encoding and control conditions identified activation in medial frontal gyrus, retrosplenial cortex and posterior inferior parietal cortex. Most importantly, only posterior inferior parietal regions showed increasing activation across sessions, thus paralleling behavioral measures of route expertise. Given the established role of the posterior parietal cortex in spatial processing, this area is thought to provide the pivotal spatial link between two landmarks encountered in immediate temporal succession.

Adult↗
PubMed2004

S-Allylcysteine prevents amyloid-beta peptide-induced oxidative stress in rat hippocampus and ameliorates learning deficits.

The effects of S-allylcysteine on oxidative damage and spatial learning and memory deficits produced by an intrahippocampal injection of amyloid-beta peptide 25-35 (Abeta(25-35)) in rats were investigated. The formation of reactive oxygen species, lipid peroxidation and the activities of the antioxidant enzymes superoxide dismutase and glutathione peroxidase were all measured in hippocampus 120 min after Abeta(25-35) injection (1 microl of 100 microM solution), while learning and memory skills were evaluated 2 and 35 days after the infusion of Abeta(25-35) to rats, respectively. Abeta(25-35) increased both reactive oxygen species and lipid peroxidation, whereas pretreatment with S-allylcysteine (300 mg/kg, i.p.) 30 min before peptide injection decreased both of these markers. In addition, Abeta(25-35)-induced incorrect learning responses were prevented in most of trials by S-allylcysteine. In contrast, enzyme activities were found unchanged in all groups tested. Findings of this work: (i) support the participation of reactive oxygen species in Abeta(25-35)-induced hippocampal toxicity and learning deficits; and (ii) suggest that the protective effects of S-allylcysteine were related to its ability to scavenge reactive oxygen species.

Amyloid beta-Peptides↗