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PubMed1988

The role of selective attention in the visuo-spatial memory of patients suffering from dementia of the Alzheimer type.

The visuo-spatial memories of groups of dements suffering from Alzheimer's disease (DAT) and multi-infarct dementia (MID) were compared with those of low-IQ but non-dementing elderly volunteers. In contrast to the other two groups, the DAT subjects were hindered when extra visual information was available as a memory aid. Similarly, DAT subjects' performance on a visual search task was worsened when the displays were made more varied. The concept that DAT patients' visuo-spatial memory problems may be due to a failure of selective attention is discussed.

Aged↗
PubMedDate not supplied

Age-related ability of rats kept on a life-long hypocaloric diet in a spatial memory test. Longitudinal observations.

Cognitive behavior was assessed in a test specific for spatial memory, according to a longitudinal experimental model, in populations of 12-, 24- and 30-month-old rats which were fed ad lib either a standard (ST) or a hypocaloric (HY) diet, that had been shown to reduce age-related pathologies and to increase survival. Already at 12 months of age, some cognitive deficits were observed in ST but not in HY rats. When retested 12 and 18 months later, the animals performed better at the beginning of the test than when tested for the first time, indicating that some aspects of previous experience lead to a preservation of spatial memory. Deficits which had been previously observed in 2-year-old groups in a cross-sectional experimental model were not evident this time. Some of the differences between the two diet groups observed 12 months before disappeared. When testing was repeated for the third time at 30 months of age, ST fed rats presented very marked deficits in learning and in memory, which were not seen in the HY group. It thus appears that a dietary regimen in which part of the calorie-rich components, such as lipids and carbohydrates, are replaced with vegetable fibers, retards some of the age-related deteriorations of brain functions.

Aging↗
PubMed1992

Intrahippocampal grafts of cholinergic-rich striatal tissue ameliorate spatial memory deficits in rats with fornix lesions.

Previous studies have shown that cholinergic grafts derived from the medial septal nucleus are capable of restoring behavioral function in rats with lesions that sever the cholinergic inputs to the hippocampal formation. In this study, we demonstrate that intrahippocampal grafts of cholinergic-rich striatal tissue also ameliorate spatial memory deficits of rats with fornix lesions. We also found that atropine administration dramatically disrupted spatial navigation performance of rats with striatal grafts and control rats, thus suggesting that the striatal graft effects are mediated by cholinergic mechanisms of action. Measurements of high affinity choline uptake (HACU) and muscarinic receptor binding revealed that intrahippocampal striatal grafts increased HACU and normalized muscarinic receptor binding in animals with fornix lesions. Regression analyses demonstrated significant correlations between the amelioration of spatial memory deficits and hippocampal HACU and receptor binding. We conclude that intrahippocampal grafts of cholinergic-rich striatal tissue can ameliorate spatial memory deficits and that this amelioration is associated with the reinstatement of functional cholinergic terminations.

Animals↗
PubMedDate not supplied

Aging and the physiology of spatial memory.

Evidence for age-related changes in spatial memory in rodents and humans is presented, along with data that suggest that the hippocampal formation is necessary for normal performance on spatial tasks in both species. An examination of the electrophysiological characteristics of this structure in rats suggests that the changes that occur with age in the hippocampus are selective, but that at least two primary types of alterations contribute to the spatial cognitive impairment seen in these animals. These include a deficit in the ability to maintain synaptic enhancement and a reduction in the accuracy of information processing ability of single hippocampal neurons.

Aging↗
PubMedDate not supplied

Exercise does not modify spatial memory, brain autoimmunity, or antibody response in aged F-344 rats.

Old F-344 rats were given endurance training over a 10-week period on a motorized treadmill. This treatment resulted in substantial heart-to-body weight ratio increases, indicative of effective training. To determine whether endurance training might alter some of the known immune system and cognitive changes observed during aging, exercised old rats were compared to nonexercised old and young controls on three variables: in vivo antigen-specific immune activity, brain-reactive antibody formation, and spatial memory. The exercise training did not influence any of these measures in the old rats. Both groups of old rats showed poorer antibody response to a specific antigen, more brain-reactive antibody formation, and poorer spatial memory than the young controls. There was, however, a significant relationship between brain-reactive antibody formation and spatial memory performance, regardless of training condition.

Aging↗
PubMed1988

Spatial memory impairment and central muscarinic receptor loss following prolonged treatment with organophosphates.

Memory impairment is one of the recurrent complaints of agricultural workers repeatedly exposed to organophosphorus insecticides. In an effort to establish an animal model for such behavioral effects, which would allow studying its underlying biochemical mechanism(s), in this study we evaluated spatial memory in animals following repeated organophosphate exposure. Male Long-Evans rats were given daily i.p. injections of either diisopropylfluorophosphate (DFP; 1 mg/kg/day) or disulfoton (O,O-diethyl S-[2-(ethylthio)ethyl] phosphorodithioate; 2 mg/kg/day) for 14 days. Acetylcholinesterase activity was inhibited 71-77% in the cortex, hippocampus, and striatum of rats treated with DFP, and 73-74% in those treated with disulfoton. Binding of [3H]quinuclidinyl benzilate ([3H]QNB) to cholinergic muscarinic receptors in the same brain areas was reduced 16-28% in organophosphate-treated rats. This decrease was due to a reduction in muscarinic receptor density (Bmax) with no changes in receptor affinity. At the end of the treatment rats were tested for spatial memory using the spontaneous alternation task in a T-maze. Rates of true spontaneous alternation were 64.4, 45.0, and 44.8% in animals which received corn oil, DFP, or disulfoton, respectively (P less than 0.05). These results indicate that prolonged inhibition of acetylcholinesterase caused by repeated organophosphate exposure alters spatial memory functions in rats, as well as causing a loss of muscarinic receptors. Considering the role of the cholinergic system in cognitive processes, these biochemical alterations could be related to the observed behavioral changes and may offer a potential explanation of the memory impairment reported by workers chronically exposed to organophosphates.

Acetylcholinesterase↗
PubMed1987

Single unit activity in the rat hippocampus during a spatial memory task.

Single unit activity was recorded from complex spike cells in the hippocampus of the rat while the animal was performing a spatial memory task. The task required the animal to choose the correct arm of a 4 arm plus-shaped maze in order to obtain reward. The location of the goal arm was varied from trial to trial and was identified by 6 controlled spatial cues which were distributed around the enclosure and which were rotated in step with the goal. On some trials these spatial cues were present throughout the trial (spatial reference memory trials) while on other trials they were present during the first part of the trial but were removed before the rat was allowed to choose the goal (spatial working memory trials). On these latter trials the animal had to remember the location of the cues and/or goal during the delay in order to choose correctly. 55 units were recorded during sufficient reference memory trials for the relationship between their firing pattern and different spatial aspects of the environment to be determined. 33 units had fields with significant relations to the controlled cues while 16 had significant relations to the static background cues, those cues in the environment which did not change position from trial to trial. Of 43 units which could be tested for their relation to the shape of the maze arms themselves, 15 showed such a relationship. Therefore the place units can be influenced by different aspects of the spatial environment but those related to the task requirement appear to be more potent. Interaction effects between the different spatial factors also influenced the firing pattern of some units. Of particular interest was the interaction between the controlled cues and the static background cues found in some cells since this might shed some light on how the hippocampus enables the rat to solve the memory task. 30 units with place fields related to the controlled cues were recorded during successful performance on spatial working memory trials as well as during spatial reference memory trials. The place fields of 90% of these units were maintained during the retention phase of the memory trials. During the recording of some units, other types of trial were given as well. On control trials, the cues were removed before the rat was placed on the maze. These trials provided controls for the potential influence of information left behind by the controlled cues and for the influence of the animal's behaviour on the unit activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1977

Spatial memory and hemispheric locus of lesion.

Corsi's cube test was given to 40 control and 80 brain-damaged patients to assess the relation of different aspects of spatial memory to the hemispheric locus of lesion. Spatial span was found affected by injury producing visual field defect (VFD), regardless of the side of the lesion. Delayed reproduction of a 3 cube sequence (which was within the span of every patient) was performed more poorly by patients with right hemisphere damage and VFD than by controls. This was true whether the delay was unfilled or filled with a counting activity, the two conditions being equally effective in bringing about the inferiority of the right brain-damaged group. Learning to criterion up to a maximum of 50 trails a supraspan sequence was failed by 65% of right brain-damaged patients with VFD, a percentage significantly higher than that found not only in the control group, but also in any other brain-damaged group. These findings point to the dominant role played by the posterior region of the right hemisphere in subserving spatial memory mechanisms, especially when the acquisition of stable traces is requested.

Brain Damage, Chronic↗
PubMed1979

Spatial memory deficit following fimbria-fornix lesions: independent of time for stimulus processing.

The present experiment examined the possible role of stimulus processing time in the spatial memory deficit found following fimbria-fornix lesions in rats. Rats were trained preoperatively on a radial arm maze in a procedure that placed them at the end of each arm and confined them there for 30 seconds. This confinement period was markedly longer than the few seconds the rats normally spend there in the usual test procedure. Rats with fimbria-fornix lesions performed no better than expected by chance on the first choice after placements. Although performance on subsequent choices was above chance, this was due to a strong turning pattern; when this pattern was interrupted, performance was no greater than that expected by chance on all choices. These data demonstrate that the deficit in the radial arm maze resulted primarily from a difficulty in spatial memory, rather than from an insufficient time for processing stimulus information.

Animals↗
PubMed1985

Dissociation between components of spatial memory in rats after recovery from the effects of retrohippocampal lesions.

A series of 4 experiments examined the performance of rats with retrohippocampal lesions on a spatial water-maze task. The animals were trained to find and escape onto a hidden platform after swimming in a large pool of opaque water. The platform was invisible and could not be located using olfactory cues. Successful escape performance required the rats to develop strategies of approaching the correct location with reference solely to distal extramaze cues. The lesions encompassed the entire rostro-caudal extent of the lateral and medial entorhinal cortex, and included parts of the pre- and para-subiculum, angular bundle and subiculum. Groups ECR 1 and 2 sustained only partial damage of the subiculum, while Group ECR+S sustained extensive damage. These groups were compared with sham-lesion and unoperated control groups. In Expt 1A, a profound deficit in spatial localisation was found in groups ECR 1 and ECR+S, the rats receiving all training postoperatively. In Expt 1B, these two groups showed hyperactivity in an open-field. In Expt 2, extensive preoperative training caused a transitory saving in performance of the spatial task by group ECR 2, but comparisons with the groups of Expt 1A revealed no sustained improvement, except on one measure of performance in a post-training transfer test. All rats were then given (Expt 3) training on a cueing procedure using a visible platform. The spatial deficit disappeared but, on returning to the normal hidden platform procedure, it reappeared. Nevertheless, a final transfer test, during which the platform was removed from the apparatus, revealed a dissociation between two independent measures of performance: the rats with ECR lesions failed to search for the hidden platform but repeatedly crossed its correct location accurately during traverses of the entire pool. This partial recovery of performance was not (Expt 4) associated with any ability to discriminate between two locations in the pool. The apparently selective recovery of aspects of spatial memory is discussed in relation to O'Keefe and Nadel's (1978) spatial mapping theory of hippocampal function. We propose a modification of the theory in terms of a dissociation between procedural and declarative subcomponents of spatial memory. The declarative component is a flexible access system in which information is stored in a form independent of action. It is permanently lost after the lesion. The procedural component is "unmasked" by the retrohippocampal lesion giving rise to the partial recovery of spatial localisation performance.

Animals↗
PubMed1990

Selective activation effects of concurrent verbal and spatial memory loads in left-handed and right-handed adults.

Thirty-two left-handed subjects, divided into four groups according to sex and familial sinistrality, and 16 right-handed subjects without familial sinistrality (8 male, 8 female) participated in a tachistoscopic unilateral letter-identification task with concurrent verbal- and spatial-memory loads. Across groups, a significant right visual field advantage for letter-identification was found. In the majority of both left-handed and right-handed subjects, the concurrent verbal-memory load resulted in a selective activation, with the right visual field performance showing improvement. However, the group of left-handed males with a positive family history of sinistrality gave less evidence of selective left-hemispheric activation as a consequence of the verbal-memory load. The concurrent spatial-memory load did not result in a consistent pattern of selective activation.

Adolescent↗
PubMed1991

Neonatal anoxia induces transitory hyperactivity, permanent spatial memory deficits and CA1 cell density reduction in developing rats.

Physical and reflex development, spontaneous behavior in open field and spatial memory abilities have been studied in rats after neonatal anoxia. Histological analysis of the hippocampal fields have been carried out in selected animals at the end of the testing period. No differences between control and anoxic rats were recorded in the physical and reflex development. Hyperactivity in open field was present in anoxic animals only transiently between P20 and P45. Spatial memory abilities, tested at two developmental stages by means of a maze and a water maze, appeared to be defectual not only during the hyperactivity period but also in adulthood. The histological analysis of the different hippocampal fields demonstrated a significant difference between anoxic and control rats in the cell density of the CA1 field. The present data demonstrate that neonatal anoxia, besides determining only transitory defects in open field behavior, profoundly affects cognitive abilities and cell density in CA1 hippocampal field. These results might be of relevance in the interpretation of the substrate of the cognitive impairment seen in hyperactive children that are exposed to hypoxia at birth.

Animals↗
PubMed1991

Disproportionate intentional spatial-memory impairments in amnesia.

Twenty-four amnesics, including patients with Korsakoff's disease, post-encephalitic amnesia and amnesia caused by rupture of an anterior communicating artery aneurysm (ACoAA), were compared with 24 matched control subjects on a task in which words were presented in any one of four positions on a computer screen and subjects were instructed to remember both the words and their locations. The patients were tested after more learning opportunity, exposure to shorter lists, and after shorter delays than were their controls in order to match the word recognition performance of the two groups. Under these conditions, the amnesics' ability to locate recognized words was significantly worse than that of their controls. Although there was a tendency for the ACoAA patients to show more severe spatial memory deficits than Korsakoff patients, there was no clear evidence that aetiology of amnesia was a critical determinant of whether spatial memory was more impaired than word recognition. It was concluded that amnesics show a disproportionately severe memory deficit for spatial information that is intentionally encoded as well as for that which is incidentally encoded.

Adolescent↗
PubMed1991

Fetal transplant-induced restoration of spatial memory in rats with lesions of the nucleus basalis of Meynert.

Bilateral lesions of the nucleus basalis of Meynert (nbM) in rats produced mnemonic deficits when subjects were tested on tests of spatial memory over a period of 3 to 7.5 months postoperatively. The transplantation of cholinergic-rich, fetal ventral forebrain tissue to either two or four frontoparietal cortical sites normalized performance on the spatial memory tasks. However, which transplant condition yielded recovery depended upon the nature of the task and/or posttransplantation interval. When assessed 8 months following transplant surgery, cortical choline acetyltransferase and acetylcholinesterase activity levels in both transplant groups were comparable to those values found in sham-operated animals. These data indicate that fetal transplants can reverse the mnemonic deficits and restore cortical cholinergic neurochemical activity to near-normal levels in rats with nbM lesions.

Animals↗
PubMed1989

Effects of captopril on locomotor activity, passive avoidance behaviour and spatial memory tasks in the trimethyltin-treated rat.

The potential neuroprotective/cognitive enhancing actions of captopril were investigated in the trimethyltin (TMT)-induced neurotoxicity rat model. Acute exposure to TMT produces alterations in locomotor activity, passive avoidance behaviour and spatial memory tasks. Captopril treatment given in combination with the single acute injection of TMT reversed the deficits in spatial memory tasks in 8 out of 25 trials. While post-treatment of TMT-treated rats with captopril brought about a significant improvement in 3 out of 25 trials, pre-treatment of rats for 3 weeks with captopril did not reverse the behavioural deficits produced by TMT in the Morris maze test. Captopril treatment did not block the characteristic hyperactivity or the deficits in passive avoidance behaviour of TMT-treated animals.

Animals↗
PubMed1986

Behavioral effects of exposure to nuclear magnetic resonance imaging: II. Spatial memory tests.

In order to determine possible effects of exposure to nuclear magnetic resonance imaging (MRI) on cognitive processes, the performance of imaged, sham exposed, and control rats on a spatial memory task was examined. This particular task was chosen because, under some conditions, animals use the magnetic field as a compass when navigating. The rats were required to collect food from eight different locations before returning to an already chosen location. All three groups of rats achieved a high level of performance, and there were no differences between groups in any of the performance measures examined. These results indicate that the MRI procedure has no significant effect on spatial memory processes in rats.

Animals↗
PubMedDate not supplied

The effects of life-long food restriction on spatial memory in young and aged Fischer 344 rats measured in the eight-arm radial and the Morris water mazes.

The effect of life-long 60% ad lib food restriction on performance in two tasks involving spatial memory, the eight-arm radial maze and the Morris water maze, was studied in young and aged Fischer 344 rats. Restricted (R) and ad lib (AL) feeding groups were compared at 8, 16, and 24 months of age on both tasks. A 30-month-old R group was also tested in the Morris water maze. In the eight-arm maze, although 24-month-old animals performed more poorly than 8- and 16-month-old animals during the first week of testing, overall accuracy of performance did not vary significantly as a function of age. Twenty-four-month-old animals took longer to make 10 choices than did younger animals, and there was a significant interaction between feeding regimen and age, reflecting the fact that at the two younger ages, R groups performed more quickly than the AL groups. In the Morris water maze, both distance swum and time to find the platform increased with age. Life-long food restriction led to small but significant improvements in performance in the water maze in aged rats. R groups showed evidence for better retention over 24-hour intervals than did AL groups. By 30 months of age, however, R animals showed impaired performance relative to younger R groups. These differential findings on the two tasks, as they were used here, suggest that there was greater impairment with age on the spatial memory task requiring retention of information over long intervals than there was on the task primarily involving working memory within a trial.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗