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PubMedDate not supplied

Sleep after learning aids memory recall.

In recent years, the effect of sleep on memory consolidation has received considerable attention. In humans, these studies concentrated mainly on procedural types of memory, which are considered to be hippocampus-independent. Here, we show that sleep also has a persisting effect on hippocampus-dependent declarative memory. In two experiments, we examined high school students' ability to remember vocabulary. We show that declarative memory is enhanced when sleep follows within a few hours of learning, independent of time of day, and with equal amounts of interference during retention intervals. Sleep deprivation has a detrimental effect on memory, which was significant after a night of recovery sleep. Thus, fatigue accumulating during wake intervals could be ruled out as a confound.

Adolescent↗
PubMed1994

Mechanism of action of 8-OH-DPAT on learning and memory.

It has been previously demonstrated that pretraining injection of 8-hydroxy-2-(di-n-propilamino)tetralin (8-OH-DPAT, a 5-HT1A agonist) impairs conditioned response (CR) in an autoshaping learning task. Therefore, in the present work we intended to determine whether such an effect could be prevented by pretraining, and whether pre- or postsynaptic 5-HT receptors are involved. Groups of rats received or did not receive food magazine training. On the next day, all groups in both conditions, pre- or posttraining, were treated with 8-OH-DPAT (0, 0.062, or 0.250 mg/kg). Posttraining groups were tested on a second session of autoshaping 24 h later. In a second experiment, naive rats received para-chlorophenylalanine (PCPA) (300 mg/kg x 3 days) before pre- or posttraining injection of 8-OH-DPAT. Results showed that in those groups trained to food magazine and treated 24 h later with 8-OH-DPAT, CR was not affected or enhanced. PCPA injection had no effect by itself, but blocked or attenuated the effect of a post- or pretraining injection of 8-OH-DPAT. The present data suggest that a) the pretraining effect of 8-OH-DPAT eliciting a decrease in CR can be eliminated by a food magazine training session; and b) presynaptic 5-HT1A receptors are involved in the effect of 8-OH-DPAT on the acquisition and consolidation of learning.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed2000

[Correlation between the age-related memory impairment and the level of free Ca(2+) in brain synaptosomes].

In this study, We investigated the changes in the ability of learning-memory of 12-month- and 18-month-old mice, and the intrasynaptosomal Ca(2+) levels of some mouse brain areas (hippocampus, cerebral cortex, corpus quadrigem and cerebellum) on the basis of our last behavior observation and biochemistry detection. Meanwhile, the intrasynaptosomal Ca(2+) levels of the four brain areas were compared between the mice of impaired and good memory. The main results are as follows. With the increase of age, the ability of learning-memory of mice decreased significantly; and the concentration of the intrasynaptosomal free Ca(2+) (i) in mouse brain areas (except for cerebral cortex) increased markedly, especially in the memory-impaired mice. The results suggest that age-related memory impairment may be associated with the overloading of intrasynaptosomal free Ca(2+) (i).

Aging↗
PubMed1998

Altered spatial learning and memory in mice lacking the mGluR4 subtype of metabotropic glutamate receptor.

The glutamate analog, L-2-amino-4-phosphonobutyric acid (L-AP4) is a selective agonist for several members of the metabotropic glutamate receptor (mGluR) family. Activation of presynaptic mGluRs by L-AP4 causes a suppression of synaptic transmission in the central nervous system. In this study, the role of 1 subtype of mGluR in the nervous system was investigated by analyzing mutant mice lacking the L-AP4-sensitive receptor, mGluR4. Experiments designed to probe hippocampal function showed no impairments in acquisition of spatial learning in the water maze task. However, in a spatial reversal learning task, the mutant mice exhibited significantly accelerated learning performance. Furthermore, in a probe trial administered 6 weeks posttraining, these mice showed impaired spatial accuracy. The results suggest that the mutant mice differed in their ability to learn and integrate new spatial information into previously formed memory traces and that their use of stored spatial information also was altered. Thus, the presynaptically expressed mGluR4 plays a role in the processing of spatial information.

Analysis of Variance↗
PubMed2006

Subdivisions of inferior temporal cortex in squirrel monkeys make dissociable contributions to visual learning and memory.

Inferior temporal cortex of squirrel monkeys consists of caudal (ITC), intermediate (ITI), and rostral (ITR) subdivisions, possibly homologous to TEO, posterior TE, and anterior TE of macaque monkeys. The present study compared visual learning in squirrel monkeys with ablations of ITC; ITI and ITR (group ITRd); or ITI, ITR, and more ventral cortex, including perirhinal cortex (group ITR+), with visual learning in unoperated controls. The ITC monkeys had significant impairments on pattern discriminations and milder deficits on delayed non-matching to sample (DNMS) of objects. The ITRd monkeys had deficits on some pattern discriminations but not on DNMS. The ITRd monkeys were significantly impaired on DNMS and some pattern discriminations. These results are similar to those found in macaques and support the proposed homologies.

Analysis of Variance↗
PubMed2000

Neural bases of learning and memory: functional neuroimaging evidence.

Positron emission tomography and functional magnetic resonance imaging studies have identified brain regions associated with different forms of memory. Working memory has been associated primarily with the bilateral prefrontal and parietal regions; semantic memory with the left prefrontal and temporal regions; episodic memory encoding with the left prefrontal and medial temporal regions; episodic memory retrieval with the right prefrontal, posterior midline and medial temporal regions; and skill learning with the motor, parietal, and subcortical regions. Recent studies have provided higher specificity, by dissociating the neural correlates of different subcomponents of complex memory tasks, and the cognitive roles of different subregions of larger brain areas.

Brain↗
PubMed1993

[Effect of intracerebroventricular injection of N-methyl-D-aspartate on learning and memory in mice].

In one trial passive avoidance response in mice, the effect of N-methyl-D-aspartate (NMDA) on acquisition, consolidation and retrieval of memory were observed after icv administration of 10 ng, 1 ng or 0.1 ng/mouse. The results showed that NMDA 10 ng/mouse could promote the consolidation of memory in step-down test and 1 ng/mouse could promote the retrieval of memory in step-through test. NMDA 1 ng/mouse significantly improved the retrieval impairment induced by 30% alcohol and the consolidation impairment induced by NaNO2 in step-down and step-through tests. The effect of NMDA on memory was antagonized by NMDA receptor antagonist, AP5. These results provide direct evidence for the action of NMDA subtype of glutamate receptor on memory.

Animals↗
PubMed1995

Selective immunotoxic lesions of basal forebrain cholinergic cells: effects on learning and memory in rats.

Male Long-Evans rats were given injections of either 192 IgG-saporin, an apparently selective toxin for basal forebrain cholinergic neurons (LES), or vehicle (CON) into either the medial septum and vertical limb of the diagonal band (MS/VDB) or bilaterally into the nucleus basalis magnocellularis and substantia innominata (nBM/SI). Place discrimination in the Morris water maze assessed spatial learning, and a trial-unique matching-to-place task in the water maze assessed memory for place information over varying delays. MS/VDB-LES and nBM/SI-LES rats were not impaired relative to CON rats in acquisition of the place discrimination, but were mildly impaired relative to CON rats in performance of the memory task even at the shortest delay, suggesting a nonmnemonic deficit. These results contrast with effects of less selective lesions, which have been taken to support a role for basal forebrain cholinergic neurons in learning and memory.

Acetylcholinesterase↗
PubMed1997

Effect of cerebellar granule cell depletion on spatial learning and memory and in an avoidance conditioning task: studies in postnatally X-irradiated rats.

Rats of the DA/HAN strain (pigmented rats) were submitted to two experimental tasks consisting in spatial learning (water escape experiment) and in passive avoidance conditioning. These rats were either totally or partially deprived of their granule cells using two different schedules of postnatal X-irradiation of the cerebellum. When they were 3 months old, the animals were submitted to an initial learning session, followed by a retrieval test seven days later. The scores of the rats which were partially deprived of granule cells appeared similar to those of controls, except for a mild deficiency of spatial learning. The learning and retrieval scores of the rats totally deprived of granule cells were similar to those of controls at the passive avoidance conditioning task, but these animals were unable to accurately learn a spatial task and showed memory impairments relative to controls. These results are discussed in terms of cognitive defects.

Animals↗
PubMed1984

An involvement of acetylcholine in object discrimination learning and memory in the marmoset.

Five marmosets (Callithrix jacchus) were tested, using a Wisconsin General Test Apparatus, on a series of junk object visual discrimination tasks, including new learning, 24-hr reversal and 24-hr retention. The effects of administering the cholinergic receptor blocking agent, scopolamine either just before or immediately after the new learning task, or just before the 24-hr reversal and retention tasks, were assessed. Results suggest that scopolamine impairs new learning and impairs the encoding of new information in long term memory. Some evidence of a mild retrieval deficit under scopolamine was also seen, while state-dependent effects were not apparent.

Acetylcholine↗
PubMed1995

Improved learning and memory in aged rats with chronic administration of the nicotinic receptor agonist GTS-21.

The ability of two synthetic nicotine receptor ligands, TGS-21 and DMAB, to chronically enhance the cognitive function of aged rats was evaluated in three diverse tasks and compared to the cognition-enhancing effects of nicotine administration. 15 min prior to daily behavioral testing, aged 22-24 month old rats received an i.p. injection of nicotine (.02 mg/kg), GTS-21 (1 mg/kg), DMAB (2mg/kg), or saline vehicle and were tested in either one-way active avoidance pole jumping, Lashley III maze, or a 17-arm radial maze. GTS-21 pretreatment was as effective as nicotine for enhancing the acquisition of aged rats in both one-way active avoidance and Lashley III maze training. In 17-arm radial maze testing, GTS-21 improved both general learning and reference (long-term) memory to the same extent as nicotine. Although DMAB pretreatment enhanced reference memory in 17-arm radial maze testing to the same as nicotine, it did not affect general learning in this complex task and did not exert any cognition-enhancing effects in Lashley III maze training. These results indicate that GTS-21 has cognition-enhancing abilities in aged rats that are comparable to those of nicotine in a variety of behavioral tasks. Since GTS-21 acts preferentially on brain nicotinic receptors and is less toxic than nicotine, thses results further indicate that GTS-21 may have substantive therapeutic value in the treatment of age-associated memory impairment (AAMI) and/or Alzheimer's disease.

Aging↗