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Results for “learning and memory”

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At least 1,081 records · Page 60Linked to original sources
PubMed2000

Spatial learning and memory deficits induced by exposure to iron-56-particle radiation.

It has previously been shown that exposing rats to particles of high energy and charge (HZE) disrupts the functioning of the dopaminergic system and behaviors mediated by this system, such as motor performance and an amphetamine-induced conditioned taste aversion; these adverse behavioral and neuronal effects are similar to those seen in aged animals. Because cognition declines with age, spatial learning and memory were assessed in the Morris water maze 1 month after whole-body irradiation with 1.5 Gy of 1 GeV/nucleon high-energy (56)Fe particles, to test the cognitive behavioral consequences of radiation exposure. Irradiated rats demonstrated cognitive impairment compared to the control group as seen in their increased latencies to find the hidden platform, particularly on the reversal day when the platform was moved to the opposite quadrant. Also, the irradiated group used nonspatial strategies during the probe trials (swim with no platform), i.e. less time spent in the platform quadrant, fewer crossings of and less time spent in the previous platform location, and longer latencies to the previous platform location. These findings are similar to those seen in aged rats, suggesting that an increased release of reactive oxygen species may be responsible for the induction of radiation- and age-related cognitive deficits. If these decrements in behavior also occur in humans, they may impair the ability of astronauts to perform critical tasks during long-term space travel beyond the magnetosphere.

Analysis of Variance↗
PubMed1999

Reading disability subtypes and the test of memory and learning.

For Study 1, 24 readers with dysphonetic dyslexia and 21 with dyseidetic dyslexia, classified by Boder criteria, were compared to 90 control group participants (45 matched for age and 45 for reading level) on the Composite Memory Index (CMI) score from the Test of Memory and Learning (TOMAL). CMI scores were significantly lower for children with dyslexia (p <.0001). Plotting average subtest score profiles for all reader groups revealed auditory sequential memory impairments for both types of readers with dyslexia, and multiple strengths for good readers. Dysphonetic and dyseidetic dyslexia profiles were nearly identical. For Study 2, average linkage cluster analysis was performed using principal components derived from subtests of the TOMAL. Homogeneous clusters of normal readers and children with reading disabilities emerged. Results indicated that qualitatively distinct subtypes of readers with dyslexia exist.

Journal Article↗
PubMedDate not supplied

Benzodiazepine impairs and beta-carboline enhances performance in learning and memory tasks.

Benzodiazepines are widely used anxiolytics and anticonvulsants, and their potent sedative properties are routinely used in presurgical anaesthesia. However, they are also known to induce a strong anterograde amnesia in patients. Specific benzodiazepine antagonists have recently been described, some of which have intrinsic pharmacological properties that are opposite to those of benzodiazepines. These have been called inverse agonists and they have been shown to be proconvulsant or convulsant whereas benzodiazepines are anticonvulsants. Inverse agonists are also anxiogenic rather than anxiolytic. Since benzodiazepines induce anterograde amnesia, we have investigated the possibility that inverse agonists might also have an opposite effect for this property and so enhance acquisition (learning) and (or) retention (memory). We report here that, in three different animal models, an inverse agonist of the beta-carboline group, methyl beta-carboline-3-carboxylate (beta-CCM), enhances animal performance in three different tasks used to investigate learning and memory.

Animals↗
PubMedDate not supplied

The effect of angiotensin II and its fragments on post-alcohol impairment of learning and memory.

Angiotensin II(1-8) (A II) and its fragments: angiotensin III(2-8) (A III), angiotensin IV(3-8) (AIV), angiotensin V (4-8) (A V) and angiotensin VI(3-7) (A VI) accelerate acquisition of avoidance response and prolong their extinction. A II fragments are devoid classical A II activities such as the effects on blood pressure and thirst. Alcohol administered chronically (for 9 weeks) depresses the ability to retrieve and acquire avoidance responses. The investigated A II fragments counteract the post-alcohol impairment of learning and memory processes (A V being somewhat less active). Fragments A IV and A VI normalize the retrieval in offspring of mothers exposed to alcohol pre- and post-natally.

Alcoholism↗
PubMed2006

DYRK1A BAC transgenic mice show altered synaptic plasticity with learning and memory defects.

Among the various phenotypes seen in Down syndrome (DS), mental retardation is the most common and most debilitating condition suffered by individuals with DS. The DYRK1A gene on human chromosome 21q22.2 encodes a subfamily of protein kinases that displays dual substrate specificities and is known to play a critical role in neurodevelopment. To study DS mental retardation, we have generated transgenic mice that contain only one copy of the complete human DYRK1A gene in a bacterial artificial chromosome. The transgenic mice showed significant impairment in hippocampal-dependent memory tasks in a Morris water maze. Interestingly, we observed shifts in both long-term potentiation and long-term depression, which suggests a role for DYRK1A in bidirectional synaptic plasticity. These mice represent the most clinically relevant DYRK1A mouse model to date and provide us a valuable tool for the in vivo study of mechanisms that underlie the learning and memory deficit in DS.

Animals↗
PubMed2007

Enhancement of learning and memory after activation of cerebral Rho GTPases.

The mechanism whereby the morphology and connectivity of the dendritic tree is regulated depends on an actin dynamics that, in turn, is controlled by Rho GTPases, a family of small GTP-binding proteins encompassing Rho, Rac, and Cdc42 subfamilies. Cytotoxic necrotizing factor 1 (CNF1), a protein toxin from Escherichia coli, constitutively activates Rho GTPases, thus leading to remodeling of the actin cytoskeleton in intact cells. Here, we show that the modulation of cerebral RhoA and Rac1 activity induced by CNF1 in mice leads to (i) rearrangement of cerebral actin cytoskeleton, (ii) enhanced neurotransmission and synaptic plasticity, and (iii) improved learning and memory in various behavioral tasks. The effects persist for weeks and are not observed in mice treated with a recombinant CNF1, in which the enzymatic activity was abolished by substituting serine to cysteine at position 866. The results suggest that learning ability can be improved through pharmacological manipulation of neural connectivity.

Actins↗
PubMed2004

Attention, learning, and memory in posttraumatic stress disorder.

This study compared attention and declarative memory in a sample of combat veterans with posttraumatic stress disorder (PTSD, n = 24) previously reported to have reduced concentrations of the hippocampal neuronal marker N-acetyl aspartate (NAA), but similar hippocampal volume compared to veteran normal comparison participants (n = 23). Healthy, well-educated males with combat-related PTSD without current depression or recent alcohol/drug abuse did not perform differently on tests of attention, learning, and memory compared to normal comparison participants. Further, hippocampal volume, NAA, or NAA/Creatine ratios did not significantly correlate with any of the cognitive measures when adjustments for multiple comparisons were made. In this study, reduced hippocampal NAA did not appear to be associated with impaired declarative memory.

Alcoholism↗
PubMed2004

Learning and memory performance in mice lacking the GAL-R1 subtype of galanin receptor.

The neuropeptide galanin induces performance deficits in a wide range of cognitive tasks in rodents. Three G-protein-coupled galanin receptor subtypes, designated GAL-R1, GAL-R2 and GAL-R3, have been cloned. The present study examined the role of GAL-R1 in cognition by testing mice with a null mutation in Galr1 on several different types of learning and memory tasks. Assessments of general health, neurological reflexes, sensory abilities and motor functions were conducted as control measures. Mutant mice were unimpaired in social transmission of food preference and the Morris water maze. In tests of fear conditioning, mutant mice were unimpaired in a delay version of cued fear conditioning. However, mice homozygous for the null mutation were impaired in a trace version of cued fear conditioning. Mutant mice were unimpaired in contextual fear conditioning, whether training was by the delay or trace protocol. General health, neurological reflexes, sensory abilities and motor functions did not differ across genotypes, indicating that the trace fear conditioning deficit was not an artifact of procedural disabilities. The findings of normal performance on several cognitive tasks and a selective deficit in trace cued fear conditioning in homozygous GAL-R1 mutant mice are discussed in terms of hypothesized roles of the GAL-R1 subtype. The generally normal phenotype of GAL-R1 null mutants supports the use of this line for identification of the receptor subtypes that mediate the cognitive deficits produced by exogenous galanin.

Animals↗
PubMed2000

Pattern segmentation in a binary/analog world: unsupervised learning versus memory storing.

We discuss the problem of segmentation in pattern recognition. We adopt the model and the general approach in the landmark paper by Wang, Buhmann and von der Malsburg (Neural Computation, (1990), 2, 94-106), and expand their model in a number of ways. We review their solution to the segmentation problem in associative memory, which consists in feature binding being expressed by synchrony relations between oscillators or populations of neurons. We extend the model by introducing a law of synaptic change, which allows the network to learn by structuring itself in response to stimuli with relevant features. We discuss the problem of interference between pattern completion and the learning of new memories. We also propose a form of multiplexing of input information taking advantage of the time-structure of the neurons' response. It is based on the assessment of analog as well as of binary properties of the stimuli and provides for an enhancement of the network's processing capacity. The relevance of the results for biological systems is pointed out.

Acetylcholine↗
PubMed1994

[Effect of bifemelane hydrochloride in rats on the improvement of the learning and memory impairments and prevention of neuronal damage following transient forebrain ischemia].

Modified four-vessel occlusion in rats caused loss of the passive avoidance response (PAR) and impaired the radial maze performance (RMP). We investigated the effectiveness of bifemelane hydrochloride (bifemelane) in restoring these abilities. After the RMP test, the hippocampal neuronal density following cerebral ischemia was observed histologically and the effect of bifemelane on it examined. Bifemelane was intraperitoneally administered at a dose of 1, 3, 10 mg/kg or 30 mg/kg twice before ischemia and daily following cerebral ischemia. The control rats were given physiological saline in the same manner. At a dose of 10 mg/kg, i.p., bifemelane significantly restored the PAR, which had been lost as a result of 5-min ischemia. At the same dose, it significantly restored the RMP, which had been impaired by 15-min ischemia and prevented neuronal damage in the CA2 region of the anterior hippocampus and the CA1, CA2 and CA3 regions of the posterior hippocampus. The correlation between the memory score and the neuronal density in the CA1 region of the posterior hippocampus was statistically significant. These results suggest that bifemelane might prevent the neuronal damage induced by ischemia and restore impaired learning and memory capabilities following cerebrovascular disease.

Animals↗
PubMed1993

Characteristics of transient cerebral ischemia-induced deficits on various learning and memory tasks in male Mongolian gerbils.

We examined the characteristics of 5-min cerebral ischemia-induced behavioral deficits in spontaneous locomotor activity and their effects on the performance of habituation (HAB), passive avoidance (PA) and 8-arm radial maze (RM) tasks in Mongolian gerbils. Performances in HAB, PA and RM were impaired within 2 days after occlusion, and gerbils showed hyperlocomotion during this period. Ten days after ischemia, the hyperlocomotion disappeared and performance in the HAB and PA was the same as that in the sham-operated group. Retention in the RM was impaired at that period, but this impairment was overcome, and retention recovered easily to the sham-operated level with a few additional trials. When the acquisition trial in the RM began at 11 days after occlusion, severe learning impairment was found. Destruction of hippocampal CA1 neurons appears from 2-3 days after ischemic insult, with most CA1 neurons having disappeared by day 7. These findings suggest that the impairment of performance in the HAB and PA within 2 days after occlusion may be related to an early phase of CA1 neuronal death and to hyperlocomotion, although the impairment of spatial learning and memory was clearly associated with CA1 injury 10 days after ischemia.

Animals↗
PubMed2000

Learning and memory in bipolar and unipolar major depression: effects of aging.

OBJECTIVE: The goal of this study was to examine the effects of aging on neuropsychological functions in bipolar and unipolar major depression. BACKGROUND: Earlier studies suggested that neurocognitive deficits in mood disorder patients correlate with duration and severity of illness and also that bipolar disorder has a more virulent course than unipolar disorder. We hypothesized that elderly patients with bipolar disorder will demonstrate greater neurocognitive dysfunction than young patients with bipolar disorder and elderly patients with unipolar disorder. METHOD: A battery of tests of general intelligence and learning and memory was administered to 79 inpatients with major depression referred for electroconvulsive therapy. With patients 60 years of age and older defined as elderly, there were 29 young and 24 elderly unipolar patients and 13 young and 13 elderly bipolar patients. RESULTS: Unipolar and bipolar patients did not differ in measures of general intelligence or global cognitive status. Generally, across tests of memory, young bipolar patients exhibited the best performance and elderly bipolar patients exhibited the poorest performance. CONCLUSIONS: The results suggest that over the course of their illness, patients with bipolar disorder experience greater deterioration in memory functions than patients with unipolar disorder. Longitudinal studies are required to support the preliminary findings of this cross-sectional study.

Adult↗