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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↗
PubMed1995

The selective 5-HT3 receptor antagonist, WAY100289, enhances spatial memory in rats with ibotenate lesions of the forebrain cholinergic projection system.

The effects of three doses (0.003, 0.03 and 1.0 mg/kg sc) of the 5-HT3 receptor antagonist, WAY 100289, on spatial learning and memory in the water maze were examined in rats before and after ibotenate lesions to the nucleus basalis and medial septal brain regions at the source of cholinergic projections to cortex and hippocampus. The representative cholinergic nicotinic and muscarinic receptor agonists nicotine (0.1 mg/kg) and arecoline (1.0 mg/kg) were also tested for comparison. Both arecoline and nicotine improved initial acquisition in rats before lesioning, in terms of latency to find a hidden platform and accuracy of search strategy. WAY100289 did not affect the performance of normal rats significantly, apart from some non-significant trends towards improvement with the highest dose. However, in animals showing transient navigational deficits in retention and relearning after lesioning, WAY100289 improved performance at all three doses, though ameliorative effects of nicotine and arecoline were more marked also in lesioned rats. These results show that WAY100289 improved spatial learning in animals impaired after lesions to cholinergic projection nuclei, which may reflect an interaction with cholinergic transmission to enhance cognitive function. However, in the present study, WAY100289 appeared to be less effective than direct cholinergic agonists.

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↗
PubMed1994

Two neuronal systems involved in short-term spatial memory in monkeys.

The investigation of the neuronal activity in the monkey cerebral cortex during the delayed spatial choice performance allowed us to develop the hypothesis about two neuronal networks supporting the operative memory. The work of one of them is based on the relay-race and reverberation principles of information transfer. Another neuronal network provides for the reliability of transfer phases of these processes. The two networks are present in both prefrontal and parietal association cortical area.

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↗
PubMed1981

Deficits in spatial memory performance induced by early undernutrition.

Recent studies have shown that rats have a remarkable ability to keep track of their spatial location. Explanations stress the involvement of a form of short-term (working) memory in which the hippocampus appears to play a major role. The hippocampus appears to be vulnerable to early undernutrition and preliminary investigations indicate that Areas CA3 and CA4 suffer the most. Ninety-day-old rats, previously undernourished prenatally and throughout lactation, were tested in an 8- and, then, a 16-arm radial maze. Significant differences were observed between the experimental and control groups on both tests, especially in the 16-arm maze. Error distributions were also significantly different with experimental animals tending to perseverate in 1 area of the maze. Differences were also observed in the time taken to make the choices and in exploratory behavior. We conclude that early undernutrition affected the spatial learning ability of the animals and that this may be due to the distortions observed in the normal growth pattern of the hippocampus.

Animals↗
PubMed1993

Hippocampus, theta, and spatial memory.

The past 18 months have witnessed interesting developments in several areas of hippocampal research. First, the mechanisms of hippocampal theta are becoming clear, as is its role in spatial coding; each theta cycle appears to act as a clock mechanism against which the firing of the place cells can be timed. Second, there has been a continued strengthening in the support for the spatial theory of hippocampal function from single unit and lesion experiments; particularly important is the finding that the deficit in (non-spatial) delayed non-match to sample memory experiments in the monkey following medial temporal lobe damage stems from the part of the cortex which surrounds the hippocampus, and not from the hippocampus itself. Third, in contrast, it is proving more difficult than originally thought to show a causal relationship between long-term potentiation at the synaptic level and place learning-induced changes in hippocampal synapses.

Animals↗
PubMed1995

Systemic or intrahippocampal cannabinoid administration impairs spatial memory in rats.

The purpose of the present study was to investigate the disruptive effects of cannabinoids on working memory as assessed in the eight-arm radial-maze. Systemic administration of delta 9-THC, WIN-55,212-2, and CP-55,940 increased the number of errors committed in the radial-maze. CP-55,940 was the most potent cannabinoid in impairing memory (ED50 = 0.13 mg/kg). delta 9-THC and WIN-55,212-2 disrupted maze-choice accuracy at equipotent doses (ED50 values = 2.1 and 2.2 mg/kg, respectively). In addition, systemic administration of each of these agents retarded completion time. Whereas the doses of delta 9-THC and CP-55,940 required to retard maze performance were higher than those needed to increase error numbers, WIN-55,212-2 was equipotent in both of these measures. On the other hand, neither anandamide, the putative endogenous cannabinoid ligand, nor cannabidiol, an inactive naturally occurring cannabinoid, had any apparent effects on memory. A second aim of this study was to elucidate the neuroanatomical substrates mediating the disruptive effects of cannabinoids on memory. Intrahippocampal injections of CP-55,940 impaired maze performance in a dose-dependent manner (ED50 = 8 micrograms/rat), but did not retard the amount of time required to complete the maze. The effects of intrahippocampal CP-55,940 were apparently specific to cognition because no other cannabinoid pharmacological effects (e.g., antinociception, hypothermia, and catalepsy) were detected. This dissociation between choice accuracy in the radial-maze and other cannabinoid pharmacological effects suggests that the working memory deficits produced by cannabinoids may be mediated by cannabinoid receptors in the hippocampus.

Analgesics↗
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↗