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At least 109 records · Page 6Linked to original sources
PubMed1991

Previous experience facilitates preservation of spatial memory in the senescent rat.

In an attempt to evaluate whether previous training antagonizes age-related memory deficits, aged rats with previous training experience were compared with aged and young naive rats in the Morris water maze test. The findings of our study indicate that experience seems to facilitate the preservation of the spatial reference memory for 12 months in the aged rat, whereas senescent naive animals showed the usual age-related memory deficits. However, experience seems task-specific since the same aged rats fail to acquire a new different task.

Aging↗
PubMed1990

In situ binding of bouton zinc reversibly disrupts performance on a spatial memory task.

Neurons with zinc in the presynaptic vesicles innervate much of the telencephalon, but the functional significance of the vesicular zinc has never been established. The present work shows that reversible binding of zinc by drug infusion into the hippocampus produces a time-locked and selective disruption of hippocampal-dependent spatial-working memory. A role for vesicular zinc in neurotransmission or neuromodulation is implied.

Animals↗
PubMed1990

Amelioration of spatial memory impairment by intrahippocampal grafts of mixed septal and raphe tissue in rats with combined cholinergic and serotonergic denervation of the forebrain.

Previous studies in the rat have shown that a serotonergic depletion greatly potentiates the learning and memory impairments produced by pharmacological or lesion-induced cholinergic blockade in the forebrain. The impairment produced by combined serotonergic-cholinergic lesions is reminiscent of that seen in memory-impaired aged rats. In the present experiment, we investigated whether grafts of cholinergic septal tissue and serotonergic mesencephalic raphe tissue, placed in the hippocampus, could reverse the severe memory impairment produced by combined cholinergic-serotonergic lesions. Adult rats were given an intraventricular injection of 5,7-dihydroxytryptamine followed by a radiofrequency lesion of the septum 1-2 weeks later. Three weeks after lesion surgery, the rats were given bilateral intrahippocampal cell suspension grafts of either fetal septal or mesencephalic raphe tissue, or both. The rats were tested for spatial learning and memory in the Morris water maze task at 4 and 10 months after grafting. At 4 months, lesioned and grafted groups were all impaired compared to the normal controls in their swim time and distance swum to find the platform, and they did not show any spatially focussed search strategy in the spatial probe trial when the platform was removed from the tank. At 10 months, the rats with mixed cholinergic and serotonergic grafts were no longer impaired compared to normals in their swim time and distance to find the platform, and they were significantly improved compared to the other grafted groups. Moreover, in the spatial probe trial, the rats with mixed cholinergic and serotonergic grafts displayed a spatially focussed search behaviour over the previous platform site, which was not seen in the lesioned control rats or in the other graft groups. Morphological analysis of the hippocampus revealed that the septal grafts produced an acetylcholinesterase-positive innervation but were totally devoid of serotonin innervation. The raphe grafts produced mainly a serotonin innervation, of both acetylcholinesterase- and serotonin-positive fibres. The results suggest that a mixture of septal and raphe tissue is required when grafted to the hippocampal formation in order to ameliorate the severe spatial learning and memory impairments produced by a combined cholinergic and serotonergic denervation, and that each of these graft types separately are not sufficient to ameliorate such deficits.

Animals↗
PubMed1989

A homing procedure for studying spatial memory in immature and adult rodents.

In this procedure, subjects learn the spatial position of one hole out of many, that allows them to escape from a large open-field into their home cage. The arena is circular and can be rotated between trials so that no proximal landmark is permanently associated with the target hole. This task is thus similar to the Morris water maze procedure, since subjects must remember the position of the escape hole relative to extra-arena cues only. In addition it allows studying the importance of olfactory cues such as scent marks in or around a hole. Since the motivation is to reach home and the motor requirement is low, this task provides a useful alternative to the Morris place navigation task for studying spatial orientation in weanling or senescent rats. Examples are given showing that various behavioural parameters provide a good estimation as how subjects learn this task.

Animals↗
PubMed1992

GABAergic mediation of indirect transsynaptic control over basal and spatial memory testing-induced activation of septo-hippocampal cholinergic activity in mice.

A neurochemical study of the transsynaptic interactions established between septal GABAergic interneurones and cholinergic septo-hippocampal neurones was conducted using mice. The effects of acute in vivo injections of either muscimol (20-500 ng/0.2 microliter), bicuculline (100 ng-1 micrograms/0.2 microliter) or saline vehicle (0.2 microliter) into the medial septum on septo-hippocampal cholinergic activity were evaluated using measures of hippocampal high affinity choline uptake at 30 min post-injection in two main groups of mice. The first (quiet control) remained in their home cages during the post-injection period whereas the second (active) were submitted, 10 min following injection to a 20-min period of spatial working memory testing in an 8-arm radial maze. Intraseptal injections of either muscimol or bicuculline produced significant (25-50%) inhibition of hippocampal cholinergic activity in quiet conditions (basal) as compared to intact or saline-injected mice. In the active groups, whereas memory testing induced significant cholinergic activation (+15-20%) in intact and saline injected mice at 30 s post-test no significant memory testing-induced activation was observed in either muscimol or bicuculline-injected mice at any dose. The role of septal GABAergic interneurones in the indirect transsynaptic control over the basal and activated states of septo-hippocampal cholinergic activity is discussed with respect to the concept that these complex neuronal interactions contribute to the physiological mechanisms involved in the modulation of working memory performance.

Animals↗
PubMed1991

The effects of reversible inactivations of the hippocampus on exploratory activity and spatial memory.

This study was aimed at testing the effects of a reversible inactivation of the ventral hippocampus on behavior in response to a change, following a period of habituation with a hippocampus that functions normally. A new dishabituation paradigm was used, which allowed the testing of visuospatial memory. A salient stimulus was placed under the glass floor of the apparatus during initial exploration and was removed during the test session. The time spent above the zone where the stimulus was initially located indicated the rats' reaction to the change. Unlike the control rats who reacted to the removal of the salient stimulus by reexploring its previous location, lidocaine-injected subjects did not display any similar searching behavior. Experiment 2 examined the hypothesis that landmarks located under the floor could help hippocampus-inactivated animals to accurately react to the change. Two objects were located either close to the stimulus or some distance away from it. Even when the objects were closely associated to the stimulus, the same failure to react to the removal of the stimulus was found in lidocaine-injected rats. However, these animals displayed a higher activity level measured by the time spent on a "neutral" zone. This behavioral pattern suggests a specific localization deficit. The method of reversible inactivation appears to be a promising approach to the study of the time course of memory process with short-term experimental paradigms such as those used in the present study.

Animals↗
PubMedDate not supplied

[Characteristics of the role of spatial memory in the choice reactions of white rats].

Behaviour of the rats, previously learnt to come back to one and the same place of reinforcement was studied in conditions of periodical changes of this place. It was found that after detection of the new place of reinforcement, the rats could optimize their behaviour according to disposition of this place. Optimization of behaviour consisted in shifts of running direction towards the new reinforcement place and (or) in selective displacements before blinds, according to the places of reinforcement in the experiment. It is suggested that an increase of the role of working memory and apparatus of probabilistic prognosis at choice lies in the basis of optimization.

Animals↗
PubMed1975

Spatial memory by blind and sighted children.

Non-verbal recall of haptically presented spatial positions by three age groups of blind and sighted children was tested under conditions varying cueing, recall type and stimulus position in a within-subject design. Slighted status was not only significant, but interacted significantly with recall type, and further with stimulus position, consistent with sequential haptic by blind and quasi-simultaneous visual processing by sighted children. Age was significant, but its only significant interaction was a relatively small one with cueing conditions and stimulus position, suggesting that the oldest group, regardless of sightedness, used verbal strategies in pre-cued conditions. The findings support the hypothesis that visual and haptic modalities of representation have demonstrably different effects on processing and efficiency in spatial recall, but counterindicate the hypothesis that these relate differentially to age. Results also suggest that a combination of cue utilization and verbal strategies is a significant, but relatively minor, factor in improvements in spatial recall.

Age Factors↗
PubMed1990

[Pharmacological correction of ketamine-impaired spatial memory of rats].

Ketamine in dose 10 mg/kg increased the number of erroneous choices of rats with spatial strategy and didn't effect searching accuracy of rats with non-spatial strategy in 8-arm radial maze. Ketamine in doses 1 and 5 mg/kg disrupted rat short-term memory in delayed response reaction. Physostigmine and aspartic acid, but not haloperidol, diminished ketamine amnesia, therefore ketamine impaired the interaction of cholinergic and glutamate/aspartatergic neurons of hippocampal areas.

Amnesia↗
PubMed1988

Transplantation of embryonic ventral forebrain grafts to the neocortex of rats with bilateral lesions of nucleus basalis magnocellularis ameliorates a lesion-induced deficit in spatial memory.

Embryonic ventral forebrain grafts containing developing cholinergic cells were transplanted to the neocortex of rats with bilateral quisqualic acid lesions of the nucleus basalis magnocellularis. A lesion-induced deficit on performance of a spatial alternation test of memory was reduced by such transplants. When the same animals were treated with the acetylcholinesterase inhibitor physostigmine (0.05 mg/kg), however, performance on the behavioral task was not further promoted, and therefore, under these conditions, the cholinergic cortical transplants appear not to be subject to modulation by anticholinesterase drugs.

Acetylcholinesterase↗
PubMed1990

Hierarchical structures: chunking by food type facilitates spatial memory.

Three experiments assessed the ability of male Sprague-Dawley rats to organize the spatial locations of different food types in a hierarchical manner to maximize the efficiency of working memory. Independent groups were exposed, on a 12-arm radial maze, to baiting arrangements varying in the stability of the pattern and type of food used as bait. Training rats with stable, differentiable baiting arrangements produced increased accuracy in choice performance, hierarchically ordered patterns of choice selection, slower growth of proactive interference when trials were massed, and the learning of the geometrical relations among food types independent of other extramaze cues. Such findings are strong evidence of the rat's ability to encode and use local cues for navigation, based on properties of the reinforcer. The application of a chunking strategy may provide for more efficient use of working memory by facilitating information storage, recall, or resetting mechanisms.

Animals↗
PubMed1989

The role of short-term visuo-spatial memory in control of rapid multi-joint prehensive movements.

How memorized visuo-spatial information influences motor control and whether this information is able to replace the feedback processing in cases of visual deprivation was studied using an unrestrained finger- and hand-movement paradigm. Nineteen right-handed subjects were asked to grasp and lift a small block with the index finger and thumb of the right hand, as quickly as possible. The efficiency of motor performance was analysed by measuring the grasping time derived from tangential velocity profiles of the fingertips. The data revealed significantly shorter grasping times under continuous visual guidance than during blind grasping. Grasping times increased under conditions with stepwise prolongation of visual deprivation time prior to the movement onset. The results support the general concept that within the first seconds of visual deprivation, stored visuo-spatial information can partly compensate for the lack of continuous visual feedback.

Adult↗
PubMed1992

[Study of the role of different types of glutamate receptors in spatial memory in rats].

A comparative study was performed to assess effects of different antagonists of glutamate receptors on spatial discrimination of rats in 8-arm radial and water mazes. Noncompetitive NMDA receptor blocker MK-801 in the dose 0.10 mg/kg and higher impaired the accuracy of performance in radial maze, whereas in the doses 0.05--0.30 mg/kg in water maze. Quisqualate IAMPA- and 2-amino-4-phosphonobutyrate (2-APB) I antagonists glutamate diethyl ester (250--500 mg/kg) and 2-APB (50--100 mg/kg), respectively, only increased time to complete radial maze performance and failed to alter choice accuracy. Both antagonists at the same doses did not affect performance of water maze task. The involvement of each type of glutamate receptors in different stages of spatial discrimination process in rats was discussed.

Animals↗
PubMed1990

Testosterone fails to reverse spatial memory decline in aged rats and impairs retention in young and middle-aged animals.

Recently, the vasopressin (AVP) innervation in the rat brain was shown to be restored in senescent rats following long-term testosterone administration. In order to investigate whether this restoration is accompanied by an improvement in learning and memory, both sham- and testosterone-treated young (4.5 months), middle-aged (20 months), and aged (31 months) male Brown-Norway rats were tested in a Morris water maze. All animals learned to localize a cued platform equally well, indicating that the ability to learn this task was not affected by sensory, motoric, or motivational changes with aging or testosterone treatment. There were no significant differences in retention following cue training. Subsequent training with a hidden platform in the opposite quadrant of the pool (place training) revealed impaired spatial learning in middle-aged and aged animals. Retention following place training was significantly impaired in the sham-treated aged rats as compared with sham-treated young rats. Testosterone treatment did not improve spatial learning nor retention of spatial information, but, on the contrary, impaired retention in young and middle-aged animals. The present results confirm earlier reports on an impairment of spatial learning and memory in senescent rats but fail to support a role of decreased plasma testosterone levels and central AVP innervation in this respect.

Aging↗
PubMed1985

Scopolamine degrades spatial working memory but spares spatial reference memory: dissimilarity of anticholinergic effect and restriction of distal visual cues.

The influence of the centrally active anticholinergic, scopolamine hydrobromide, on working and reference memory was studied in rats tested in a 12-arm radial maze. Both 0.25 and 0.5 mg/kg doses of the drug increased the number of working memory (WM) errors but had no effect on reference memory (RM) errors. A lower dose (0.125 mg/kg) was ineffective, as was the peripherally active anticholinergic, scopolamine methylbromide (0.5 mg/kg). Some of the behavioral effects of anticholinergics on spatial memory are mimicked by blindness or eliminating distal visual cues. If distal visual cues were more important for maintaining accurate WM than for RM, the selective effect of scopolamine on WM could be easily explained. But surrounding the maze with a curtain to eliminate extramaze cues increased RM errors without significantly increasing WM errors. Thus, the selective effect of anticholinergies on spatial memory in the radial maze is qualitatively different from the effect of restricting distal visual cues and must arise from some other action of the drug.

Animals↗
PubMed1988

Galanin impairs acquisition but not retrieval of spatial memory in rats studied in the Morris swim maze.

The effect of intraventricular administration of the neuropeptide galanin on acquisition and retrieval in a modified Morris swim maze was studied in rats. Galanin induced a significant deficit in the acquisition of the task while no effects on the retrieval were observed. No deficits were seen 24 h after the last treatment. Galanin did not increase the number of failures to reach the platform. It is suggested that endogenous galanin modulates learning possibly via the galanin-containing cholinergic neurons in the septum-basal forebrain area projecting to the hippocampus and cortex.

Animals↗
PubMed1991

Transgenic mice for the amyloid precursor protein 695 isoform have impaired spatial memory.

Transgenic mice for the human amyloid precursor protein 695 (APP695) isoform may provide an animal model of Alzheimer's disease (AD). To evaluate this, the spatial learning abilities of transgenic and wild strain mice were compared in the Morris water maze task. The transgenic mice were significantly retarded in initial learning and in learning a new escape location, although in each case they eventually reached control levels. The transgenic mice also showed slower swimming speed and reduced nocturnal activity, which may contribute to their deficit in spatial learning. Preliminary neuropathological investigations failed to reveal amyloid depositions. Thus, a gene dosage effect of APP695 may account for the memory impairment but not the plaque formation associated with AD.

Amyloid beta-Peptides↗