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PubMed1988

Young and older adults' use of context in spatial memory.

We evaluated the hypothesis that older adults remember spatial information less well than younger adults because they use contextual information less effectively. Young and older adults studied schematic town maps on which structures were presented either simultaneously or successively and on which a network of streets was either present or absent. However, age did not interact with either contextual variable. Thus, we conclude that age differences in spatial memory do not arise from differences in the use of context.

Adult↗

PubMed1989

Constraints on priming in spatial memory: naturally learned versus experimentally learned environments.

In four experiments, we explored constraints on priming in spatial memory. In Experiments 1 and 2, subjects who were familiar with the locations of buildings on the Vanderbilt campus participated in a recognition test. The subjects' task was to decide whether or not named buildings were on the campus. Foils in this recognition test were realistic but fictional names of buildings. In principle, the subjects could have performed this task without using spatial knowledge; in fact, they must not have used spatial knowledge, because there was no evidence of priming in recognition as a function of the spatial relations between buildings on the campus. This result differs from those obtained in earlier experiments that have examined memory of spatial layouts learned in laboratory settings. In Experiment 3, the fictional foils were replaced by names of buildings in an area of the campus separated geographically from the main campus. Evidently, this change induced subjects to retrieve spatial knowledge, because the spatial priming effect materialized. A fourth experiment replicated the above findings in a single experiment and demonstrated that spatial priming could be obtained when the configuration of buildings was learned experimentally. These results are explained by appealing to the "decontextualization" that takes place in memory over time.

Adult↗

PubMed1978

Non-spatial memory after selective prefrontal lesions in monkeys.

Separate groups of monkeys were trained on delayed object alternation, delayed object matching, and delayed color matching, after which half the animals in each group received lesions of the cortex in the principal sulcus, and the other half, lesions of the inferior frontal convexity. The inferior convexity lesions produced severe and lasting impairments on all three tasks, perhaps as a result of the perseverative disorder that has been associated with damage to this region. By contrast, the principal sulcus lesions, which yield such severe deficits on spatial memory tasks, led to only small, transient disruptions on each of the three non-spatial tasks. According to these results, the non-spatial memory deficits that have been found after unrestricted lateral prefrontal lesions are due mainly to damage below the principal sulcus in the inferior prefrontal cortex. The function of the tissue in the principal sulcus itself, on the other hand, appears so far to be limited largely to the spatial modality.

Animals↗

PubMed1989

Chronic phosphatidylserine treatment improves spatial memory and passive avoidance in aged rats.

Learning/memory deficits in senescent animals are widely used as a tool to evaluate the therapeutic potential of agents for treatment of age-associated cognitive dysfunction. As assessed in the Morris water maze test, aged (21-24 months) rats showed a variable loss of spatial memory. Aged non-impaired rats performed as well as young subjects, while aged impaired rats exhibited a severe and persistent place-navigation deficit. Passive avoidance retention was similarly affected in the two aged subpopulations. Chronic oral administration of phosphatidylserine (50 mg/kg/day for up to 12 weeks), a pharmacologically active phospholipid, was found to improve both the spatial memory and the passive avoidance retention of aged impaired rats. Results are discussed with reference to the phosphatidylserine-induced improvement of age-associated deterioration of brain functions in rats.

Aging↗

PubMed1986

Exponential decay of spatial memory of rats in a radial maze.

The persistence of spatial memory of rats (n = 14) was investigated in an eight-arm radial maze. The animals were trained until the mean number of errors in the first eight choices was 0.2. The decay of performance with time was studied using delays of 5, 20, 60, 120, or 240 min between choices 4 and 5, during which the animal was removed from the apparatus. A delay of 60 min significantly impaired performance. The mean number of errors was not significantly different from the random choice level after a delay of 120 min. The increase in the number of errors with time was exponential. Comparison of the results with those of previous studies suggests that the nature of training may have effects on memory persistence in the radial maze.

Animals↗

PubMed1985

Effects of opiate antagonists on spatial memory in young and aged rats.

The effects of post-training opiate antagonist administration on spatial memory were assessed in young and aged male Long Evans rats. In Experiment I rats were trained to visit each arm of an eight-arm radial maze once in a session to obtain a food reward placed at the end of each arm. During training aged rats required significantly more trials to achieve criterion performance when compared to young mature rats. However, administration of the opiate antagonist naloxone (2.0 mg/kg) immediately after each training trial did not significantly alter the rate of achieving accurate performance in either age group. In Experiment II young and aged rats that were previously trained to a comparable criterion on the radial maze were tested on the same maze apparatus in novel spatial environments. When animals were exposed to novel spatial information, the effects of post-trial opiate antagonists were examined using a within-subjects counter-balanced design. In Experiment IIa naloxone (2 mg/kg) enhanced the performance of both young and aged rats. In Experiment IIB naltrexone (1.0 mg/kg) was found to have a comparable effect of enhancing the performance of both age groups. In addition, in Experiment IIb a significant age-related deficit was found in rats tested in novel spatial environments. These results indicate that opiate antagonists are capable of improving memory for new spatial information in both young and aged rats on a task that is sensitive to behavioral deficits during normal aging.

Age Factors↗

PubMed1988

Effects of opioid microinjections into the medial septal area on spatial memory in rats.

Recent work has demonstrated that posttraining systemic opioid antagonist administration facilitates the acquisition of a radial arm maze task in new spatial environments. In this study, we examined the effect of posttraining naloxone and beta-endorphin microinjections into the medial septal area on the acquisition of a radial maze task in new spatial environments. The results of these experiments demonstrated that posttraining intraseptal naloxone administration facilitated, whereas posttraining intraseptal beta-endorphin administration impaired, the acquisition of criterion performance on a maze task performed in new spatial environments. Further, intraventricular beta-endorphin administration did not produce effects that were comparable to those observed following intraseptal beta-endorphin administration, which indicates that the septal region is a brain site that is sensitive to the effects of opioids on spatial memory in new environments. Further, posttraining intraseptal beta-endorphin administration had no effect on working memory in a familiar spatial environment, whereas pretraining intraseptal beta-endorphin administration had no effect on the performance of a previously acquired spatial task.

Animals↗

PubMed1992

Unexceptional spatial memory in an exceptional memorist.

Rajan Mahadevan evidences an exceptional memory for arrays of digits. We tested whether Rajan's spatial memory was likewise exceptional. Eight control Ss and Rajan were instructed to remember the position and orientation of 48 images of common objects shown either to the left or the right of fixation and facing either left or right. Rajan's accuracy for judging whether the position and orientation of these pictures had changed when they were shown in a different sequence was lower than that of control Ss for both judgments. Rajan's exceptional memory capacity apparently does not extend to spatial relations.

Adult↗

PubMed1985

Spatial memory in rats: electroconvulsive shock selectively disrupts working memory but spares reference memory.

In two experiments rats were trained until they displayed highly accurate spatial memories when a 4-h delay was imposed between the to-be-remembered event (TBRE) and the retention test in a 12-arm radial maze. If the procedure tested only working memory (WM) electronvulsive shock (ECS) 2 h after the TBRE produced amnesia but ECS immediately after the TBRE was ineffective. If the testing procedure also involved a reference memory (RM) component, ECS degraded WM regardless of whether it was given 0 or 2 h after the TBRE. RM was not affected. With either training procedure administering ECS 2 h before the TBRE was ineffective. Thus, in the radial maze truly old spatial RM was immune to disruption by ECS while more recent WM was vulnerable. Possible explanations of the data are presented.

Animals↗

PubMed1986

Kindling of the hippocampus induces spatial memory deficits in the rat.

Since kindling produces electrophysiological and morphological changes in the brain area stimulated, it may well affect behavioural functions dependent on the kindled area. Using an 8-arm maze, it was found that hippocampal kindling can induce specific memory deficits in spatial tasks. Reference (long-term) memory as well as working (short-term) memory were impaired. The largest impairment was observed during the period in which generalized convulsions occurred. Working memory but not reference memory impairment was reversible. Hippocampal kindling may be a useful experimental model for investigating behavioural deficits correlated with epileptogenesis.

Animals↗

PubMed1991

Evidence against a specific effect of cholinergic drugs on spatial memory in primates.

A scopolamine-like delay-dependent impairment in spatial delayed response performance in rhesus monkeys was induced by irrelevant interpolated activity or by using extended retention intervals. Physostigmine readily reversed the effects of scopolamine but had no effect on performance in young monkeys performing an irrelevant distractor task or in monkeys tested using extended retention intervals. Reducing stimulus control did not impair performance and did not alter the dose-response curve for induction of a deficit by scopolamine. Reducing the stimulus presentation time impaired performance across all retention intervals in a way which did not resemble the effect of scopolamine and which disappeared with practice. Our findings do not support the proposal that physostigmine interacts specifically with short-term spatial memory in primates.

Animals↗

PubMedDate not supplied

Selective improvement of aged rat short-term spatial memory by 3,4-diaminopyridine.

Young (10 month) and old (28 month) Fischer 344 rats were injected (IP) with 3,4-diaminopyridine (3,4-DAP) or saline 10 minutes before training on two tests of spatial memory (the Barnes circular platform and the radial 8-arm maze). This agent has been found to block potassium channels in neurons, thereby increasing calcium influx, prolonging the action potential, and leading to increased transmitter release. The circular platform task assessed the drug's effect on spatial reference memory over 24 hour intertrial intervals, and the radial maze assessed its effect on short-term working memory within a 5 minute test session. 3,4-DAP was found to selectively improve memory performance of the old animals, and, within that age group, only improved performance on the short-term memory task. 3,4-DAP may therefore be effective for only a restricted set of age-related memory problems.

4-Aminopyridine↗

PubMed1992

Amygdala kindling-induced seizures selectively impair spatial memory. 1. Behavioral characteristics and effects on hippocampal neuronal protein kinase C isoforms.

Protein kinase C (PKC) comprises a family of kinases consisting of nine subspecies that are differentially distributed in the central nervous system. This implies distinct functions. Its involvement is suggested in cellular and molecular mechanisms by which the hippocampus exerts influence on information processing. In this study, it was questioned whether abnormal activity in the neuronal substrate, particularly the hippocampal formation, induced by amygdala kindling indeed impairs spatial memory performance and correlated alpha, beta I/II, and gamma PKC subspecies expression. Rats were trained in a spatial discrimination task (SDT) and simultaneously kindled in the amygdala to induce abnormal, epileptiform activity. Control rats were only trained in the holeboard, a "free choice" maze, in which working (WM) and reference memory (RM) were simultaneously examined. Halfway through and at the end of the experiments the influence of kindling and SDT training on the immunoreactivity for PKC subspecies alpha, beta I/II, and gamma was evaluated in the hippocampal formation. Kindling resulted in a gradual increase in afterdischarge duration and motor seizure (MS) severity. Repeated SDT training ultimately resulted in an asymptotic level of WM and RM performance. As soon as generalized MSs developed, kindled rats failed to improve RM, whereas WM was not influenced. Compared to untrained rats, in trained controls PKC gamma but not PKC alpha beta I/II immunoreactivity was elevated in CA1 pyramidal and dentate gyrus granular cells. Generalized but not partial MSs abolished these alterations in PKC gamma immunoreactivity. The present data indicate that repeated training in a SDT affects the expression of PKC subspecies gamma but not of alpha or beta in the rat hippocampus. Generalized epileptiform activity impair both acquisition of new spatial RM information and PKC gamma expression. It is argued that PKC gamma plays a role in cellular mechanisms through which pathological brain activity impairs certain aspects of spatial memory.

Amygdala↗

PubMedDate not supplied

Preservation and loss of spatial memory in aged rats and humans: implications for the analysis of memory dysfunction in dementia.

Research with laboratory rats and humans demonstrating that the usual age-related deficits in spatial working memory can be attenuated or eliminated by prior training earlier in adult life is reviewed and possible mechanisms for this phenomenon are considered. A new technique for measuring remote memory for spatial information in humans is described and preliminary results with demented patients are discussed.

Aging↗

PubMed1986

Deficits in spatial-memory tasks following lesions of septal dopaminergic terminals in the rat.

The behavioral effects of 6-hydroxydopamine, injected bilaterally into the lateral septum, were investigated in two tests of spatial memory (radial 8-arm and T-maze). Three different experiments were conducted in the radial maze. In experiment I, rats were permitted to learn the task with food reinforcement in all arms of the maze. In experiment II, retention of the spatial information (working memory) learned in experiment I was tested by interposing various time intervals between choice 4 and 5 of each trial. In experiment III, reference and working memory were simultaneously assessed by only reinforcing 4 choices in the radial maze. Performances were compared in spaced versus massed trials. In the T-maze, the rats were first tested for learning a spatial discrimination between the two arms of the maze, and subsequently for reversal of the previously learned response. The results showed that the rats with lesions were impaired in all experiments. This impairment was particularly marked in some aspects of the procedures used: (1) in the search for the last 4 pellets in experiment I, (2) in the first presentations of various intervals interposed between choices 4 and 5, (3) in the search for food in the baited arms when the trials were massed in experiment III and (4) in the reversal of previously learned spatial discrimination in the T-maze. These behavioral deficits in the rats with septal dopaminergic lesions were interpreted as an increased susceptibility to interference. The lesions were shown to have selectively depleted dopamine concentrations in the septum without damaging noradrenergic terminals or cholinergic cell bodies. It was concluded that dopaminergic neurons could have a modulatory influence on memory processes.

Animals↗

PubMed1988

A long-acting cholinesterase inhibitor reverses spatial memory deficits in mice.

The effects of the long-acting acetylcholinesterase (AChE) inhibitor, galanthamine, on spatial memory were investigated in mice. Mice received ibotenic acid or sham lesions to the nucleus basalis magnocellularis (nBM). Groups of nBM-lesioned and control mice were then trained on a modified Morris swim maze task. Each mouse was first placed on a platform and then into quadrants of the swim tank in a random order. Time required to find the hidden platform was measured. In different phases of testing, the animal had to find a platform that either remained in the same quadrant (reference memory component) or was moved daily (working memory component). The nBM-lesioned mice took significantly longer to find the platform as compared to controls on the working, but not on the reference, memory component of the task. Galanthamine (5.0 mg/kg, IP), given 3.5 hours before testing, improved performance on the working memory task in nBM-lesioned mice by 70% and strikingly impaired performance in controls. Galanthamine's ability to reverse cognitive deficits induced by nBM lesions and its comparatively long half-life suggest that it may be effective in treating the central cholinergic deficits in Alzheimer's disease patients.

Animals↗

PubMed1991

Species differences in spatial memory among Clark's nutcrackers, scrub jays, and pigeons.

An operant nonmatching to sample procedure was used to compare the spatial memory abilities of 3 avian species. A trial consisted of the presentation of a spatially defined sample, a delay interval, and a 2-choice test during which the correct location was the new location. A single spatial location served as the sample in Experiment 1. The delay interval was manipulated using a titration procedure. In Experiment 2, 1, 2, or 3 sequentially illuminated locations served as the sample. The delay was 1 of 4 predetermined intervals. In Experiment 3, sample presentation was the same as Experiment 2, but the delay interval was titrated. In all of the experiments, the performance of nutcrackers was consistently better than the performance of scrub jays and pigeons (Experiment 1) and was correlated with differences in their foraging ecology.

Animals↗

PubMed1989

Raphe cells grafted into the hippocampus can ameliorate spatial memory deficits in rats with combined serotonergic/cholinergic deficiencies.

The ability of embryonic raphe cells grafted into the hippocampus to restore spatial learning ability was tested in rats with combined serotonergic/cholinergic deficits. Embryonic raphe cells (E14) were transplanted into the hippocampus of serotonin-depleted rats. Two to 3 months after transplantation, control, lesioned and grafted rats were tested in a spatial memory task (a water maze) with and without the addition of atropine. All 3 groups could negotiate the water maze equally well, in non-drug conditions. The injection of atropine caused a severe disruption of performance only in the serotonin depleted rats. The presence of an active serotonergic graft was examined in the intact rat hippocampus using the serotonin releasing drug fenfluramine (FFA). A pronounced depression of hippocampal EEG was observed in control and grafted but not in lesioned rats 15 min after the injection of FFA. These results suggest the involvement of serotonin in cognitive functions in the rat. Furthermore, it is suggested that an interaction between serotonergic and cholinergic neurotransmission occurs in the hippocampus.

Animals↗