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PubMed2004

Encoding versus retrieval of spatial memory: double dissociation between the dentate gyrus and the perforant path inputs into CA3 in the dorsal hippocampus.

The hippocampus is an essential neural structure for spatial memory. Computational models suggest that the CA3 subregion of the hippocampus plays an essential role in encoding and retrieval of spatial memory. The perforant path (PPCA3) and dentate gyrus (DG)-mediated mossy fibers (MFs) compose major afferent inputs into CA3. A possible functional dissociation between these afferent inputs was attempted using a simple navigation test (i.e., the modified Hebb-Williams maze). Behavioral testing was combined with electrolytic lesions of PPCA3 or neurotoxic lesions of the DG, to eliminate each afferent input into CA3. Lesions in either afferent input into CA3 affected learning of an effective navigational path on the maze. The contributions of the two CA3 afferent inputs, however, were different regarding encoding and retrieval of memory measured based on indices operationally defined for the behavioral paradigm (i.e., encoding, the number of errors reduced within a day; retrieval, the number of errors reduced between days). The DG-lesioned animals exhibited deficits regarding the encoding index, but not the retrieval index, whereas the PPCA3-lesioned rats displayed deficits regarding the retrieval index, but not the encoding index. The results suggest that the two major afferent inputs of CA3 may contribute differentially to encoding and retrieval of spatial memory.

Animals↗

PubMed1996

Restraint stress reversibly enhances spatial memory performance.

The effects of restraint stress on performance of a spatial memory task, the eight arm radial maze, was examined in rats. When stress was given for 6 h/day for 7 days and performance evaluated days 10-13 post stress, no effect on performance was noted; however, daily restraint stress for 13 days caused a small, but significant, enhancement of performance days 10-13 post stress. Stressed rats performed better than controls: their number of correct choices in the first 8 visits was higher than the controls, and stressed rats took fewer total choices to finish the maze than controls. Stress-dependent, enhanced performance does not appear permanent since further maze testing on days 14 and 15 post stress showed no differences between the groups. Performance of the stressed rats significantly correlated with their stress-induced, serum corticosterone levels measured after 6 h of restraint on the last day of restraint, day 13 (r = -0.63, P < 0.05); rats with higher levels of CORT took fewer choices to finish the task. Examination of hippocampal CA3c pyramidal neurons with Golgi techniques showed no effect of stress on the basal or apical dendritic arbors. Since our previous study showed that 21 days of restraint stress is associated with impaired spatial memory performance (10), these results suggest that the duration of stress may differentially affect learning/memory with shorter periods of stress serving an adaptive function while longer durations causing maladaptive changes.

Animals↗

PubMed2006

[The functional cooperation of the hippocampus and anterior thalamus via the fimbria-fornix in spatial memory in rats].

This study examined whether the cooperation of the hippocampus, and anterior thalamus via the fimbria-fornix is involved in the spatial memory. We compared the effect of contralateral lesions (Contra) with ipsilateral lesions (Ipsi) of the fimbria-fornix and anterior thalamus on the performance of an object exploration task and the Morris water maze task. If the hippocampus and anterior thalamus take part in a same functional system via fornix, the performance of Contra group will be more disruptive than that of Ipsi group. In the object exploration task, Contra and Ipsi groups did not differ from Control group in the performance of object recognition test. However, the performance of Contra group was significantly impaired in the spatial recognition test, compared with two other groups. In the Morris water maze task, only Contra group showed deficits in spatial learning but not the Ipsi group. These results indicate that contralateral, but not ipsilateral lesion caused deficits in spatial memory, supporting the notion that the functional cooperation of hippocampus and anterior thalamus via fornix is vital for spatial memory.

Animals↗

PubMed2004

Norleucine1-Angiotensin IV alleviates mecamylamine-induced spatial memory deficits.

The brain angiotensin AT4 receptor subtype has been implicated in cognitive processing. We initially established that intracerebroventricular administration of the nAChR-antagonist mecamylamine (mec) interfered with spatial memory performance in male Sprague-Dawley rats. Next we demonstrated that mec-induced deficits in spatial memory were overcome by the AT4 receptor-agonist Norleucine1-Angiotensin IV (Nle1-Ang IV). Nle1-Ang IV could not, however, compensate for spatial learning impairments precipitated by both mec and the mAChR-antagonist scopolamine. These findings support the importance of the AT4 receptor in cognitive processing and suggest that the ability of Nle1-Ang IV to improve spatial memory deficiencies may be dependant upon the brain cholinergic system.

Angiotensin II↗

PubMed1986

Pilocarpine and physostigmine attenuate spatial memory impairments produced by lesions of the nucleus basalis magnocellularis.

The effects of bilateral ibotenic acid-induced lesions of the nucleus basalis magnocellularis (nBM) on the acquisition and retention of several spatial memory tasks were studied in the rat. Maintenance of spatial memory in a food search task was impaired following nBM lesions. Acquisition of spontaneous alternation and reinforced alternation in a T-maze was also significantly impaired in animals with these lesions. In contrast, the animals with nBM lesions were not impaired in the acquisition of a position habit in a T-maze. In several of the tasks there was evidence of some learning in the lesion animals after substantial training, although they were significantly deficient when compared with the controls. Administration of the cholinergic agonists physostigmine sulfate or pilocarpine nitrate prior to behavioral testing resulted in a rapid and significant improvement in the performance of the lesion animals. The ibotenate-induced lesions significantly reduced the activity of choline acetyltransferase (CAT) in the anterior and the posterior neocortex. Hippocampal CAT activity was not changed. The results indicate that the cholinergic projections originating in the nBM are involved in the learning and memory of spatial tasks.

Animals↗

PubMed1994

Gorillas' (Gorilla gorilla gorilla) spatial memory in a foraging task.

The spatial memory of 2 gorillas (Gorilla gorilla gorilla) was explored in a simulated foraging task. Trials consisted of 2 parts separated by a delay. In the 1st part, half of the total number of food sites were baited with a highly preferred food, and the subject was allowed to search, find, and consume these items (search phase). During the delay the same locations were again baited. After the delay the animal was reintroduced to the test enclosure and allowed to search through the sites again (re-search phase). In Experiment 1, an adult gorilla was very accurate in remembering locations that had previously contained food at delay intervals of 24 hr or more. In Experiment 2, a juvenile gorilla was also accurate in remembering locations that had previously contained food at delays up to 10 min. The adult gorilla appeared to use a counting strategy during the search phase to minimize the number of sites visited.

Animals↗

PubMed1993

Variable-interval probe test as a tool for repeated measurements of spatial memory in the water maze.

Probe tests provide an important additional converging operation to identify the characteristics of cognitive processes being assessed by other behavioral measures. We introduce a new procedure using a variable-interval (VI) probe test to assess spatial memory in the water maze. Three groups of rats were trained in spatial discrimination with traditional platform trials. For the probe trials, 2 groups had no-platform (NP) probe trials in which the escape platform was unavailable for the entire trial. The 3rd group had variable interval (VI) probe trials, in which the escape platform was available only after a VI. The VI probe trial was a more sensitive measure of spatial memory than was the NP probe trial and was useful for repeated measurements of spatial memory, a characteristic not readily attainable with the NP probe trial.

Animals↗

PubMed2003

Does the radial arm maze necessarily test spatial memory?

Since its design 25 years ago (Olton & Samuelson, 1976), the eight-arm radial maze has become very popular and is now widely used to assess spatial memory in rodents. Two versions of the full-baited maze protocol are present in the literature: with or without confinement between the visit of each arm. The confinement was introduced by Olton himself as early as 1977 (Olton, Collison, & Werz, 1977) to eliminate stereotypic behaviors that he had previously observed. It is widely regarded that the confinement prevents rodents from developing these response patterns, and as such it is considered an improved procedure to test spatial memory. Surprisingly, to the best of our knowledge, no study has been especially designed to demonstrate the efficacy of the confinement in blocking the stereotypic behaviors of the animals. The present study compares the strategies of rats trained with or without a confinement procedure. The results show that, after nine days of training, rats submitted to a 5- or a 10-s confinement reach the same level of performance as rats without confinement. The confinement totally prevents stereotypic behaviors like clockwise serial searching strategies which are often observed without confinement. Even a 0-s confinement is sufficient to prevent clockwise strategies, but rats seem to develop other stratagems which do not imply spatial memory. Furthermore, rats previously trained without confinement are unable to perform the task when confinement is introduced on a test day. In contrast, rats previously trained with confinement perform the task correctly when the confinement is no longer present. Thus, without confinement, good levels of performance can be achieved without precise spatial representations.

Animals↗

PubMed2004

Allocentric spatial memory in humans with hippocampal lesions.

An immersive virtual reality (IVR) system was used to investigate allocentric spatial memory in a patient (PR) who had selective hippocampal damage, and also in patients who had undergone unilateral temporal lobectomies (17 right TL and 19 left TL), their performance compared against normal control groups. A human analogue of the Olton [Olton (1979). Hippocampus, space, and memory. Behavioural Brain Science, 2, 315] spatial maze was developed, consisting of a virtual room, a central virtual circular table and an array of radially arranged up-turned 'shells.' The participant had to search these shells in turn in order to find a blue 'cube' that would then 'move' to another location and so on, until all the shells had been target locations. Within-search errors could be made when the participants returned to a previously visited location during a search, and between-search errors when they revisited previously successful, but now incorrect locations. PR made significantly more between-search errors than his control group, but showed no increase in within-search errors. The right TL group showed a similar pattern of impairment, but the left TL group showed no impairment. This finding implicates the right hippocampal formation in spatial memory functioning in a scenario in which the visual environment was controlled so as to eliminate extraneous visual cues.

Adult↗

PubMed1992

Spatial memory and adaptive specialization of the hippocampus.

The hippocampus plays an important role in spatial memory and spatial cognition in birds and mammals. Natural selection, sexual selection and artificial selection have resulted in an increase in the size of the hippocampus in a remarkably diverse group of animals that rely on spatial abilities to solve ecologically important problems. Food-storing birds remember the locations of large numbers of scattered caches. Polygynous male voles traverse large home ranges in search of mates. Kangaroo rats both cache food and exhibit a sex difference in home range size. In all of these species, an increase in the size of the hippocampus is associated with superior spatial ability. Artificial selection for homing ability has produced a comparable increase in the size of the hippocampus in homing pigeons, compared with other strains of domestic pigeon. Despite differences among these animals in their histories of selection and the genetic backgrounds on which selection has acted, there is a common relationship between relative hippocampal size and spatial ability.

Adaptation, Physiological↗

PubMed1983

Characteristics of spatial memory in pigeons.

Pigeons learned a delayed-alteration (DA) task in a T-maze. Very few trials were needed prior to accurate performance. Similarly, after little training the birds performed accurately with delays of 8-16 min. End-of-delay cues, possibly provided by the experimenter, response-based cues, and intramaze cues were all experimentally examined and rejected as bases for the birds' performances; pigeons appear to rely on spatial (extramaze) cues. Long-delay performances were undisturbed by changes in delay-interval stimuli (illumination shifts and transportation around the laboratory). Finally, birds were shown to acquire DA so quickly because of a potent tendency to avoid recently visited locations (i.e., a preexisting "win-shift" tendency). Characteristics of pigeon spatial memory thus include temporal persistence, resistance to retroactive interference, and a win-shift bias. In these respects spatial memory of pigeons parallels spatial memory of rats.

Animals↗

PubMed1992

Vasopressin administration via microdialysis into the septum interferes with the acquisition of spatial memory in rats.

The role of vasopressin (AVP) in the septohippocampal system in spatial memory was studied in 27 male hooded rats of the Long-Evans strain. The rats were implanted with a septal microdialysis probe and assigned to 3 groups. Two days later, they were trained on 3 consecutive days (12 daily trials) to locate the hidden underwater platform in the Morris water maze (MWM) while the probes were perfused with either artificial cerebrospinal fluid (aCSF) or aCSF containing vasopressin or the V1 antagonist d(CH2)5Tyr(Me)AVP (AAVP). Another group of rats (n = 8) remained untreated. Groups receiving microdialysis of aCSF or AAVP acquired the MWM task at the same rate as untreated animals. On the other hand, place navigation learning was significantly impaired by microdialysis of AVP during all sessions. The results indicate that endogenous AVP (at least that affecting the V1 receptor subtype) is not indispensable for the acquisition of spatial memories in the MWM, whereas excessive presence of synthetic AVP interferes with spatial learning.

Animals↗

PubMed1983

Opiate antagonists, morphine and spatial memory in rats.

To assess the possible role of endogenous opioids on spatial memory, rats were administered morphine (1-15 mg/kg), naloxone (1-10 mg/kg), or naltrexone (0.1-10 mg/kg) at varying times after or prior to completing the first 4 choices in an 8 arm radial maze. None of these agents consistently affected retention, suggesting that endogenous opioid systems do not play a major role in modulating neural mechanisms that maintain accurate spatial memory.

Animals↗

PubMed1998

Reduced dorsal hippocampal glutamate release significantly correlates with the spatial memory deficits produced by benzodiazepines and ethanol.

Memory deficits frequently occur after taking benzodiazepines and ethanol. We studied in vivo hippocampal presynaptic glutamate transmission in conjunction with memory deficits induced by benzodiazepines and ethanol in rats as an animal model of amnesia. These drugs potently impaired spatial memory formation as evaluated by the Morris water maze task, the rank order among tested treatments being the combination of triazolam (20 micrograms/kg) with ethanol (2 g/kg) > or = triazolam (100 micrograms/kg) > ethanol (2 g/kg) > or = triazolam (20 micrograms/kg) > rilmazafone (20 micrograms/kg). On the other hand, these drug treatments also reduced glutamate release in the dorsal hippocampus but not in the cerebellum measured by microdialysis: the combined administration of triazolam with ethanol potently inhibited glutamate release to 60% of basal output in the dorsal hippocampus. These decreases in hippocampal glutamate transmission closely correlated with the extent of impairment of spatial memory performance (r = 0.990). Thus, the present results strongly indicated that presynaptic dysfunction in dorsal hippocampal glutamatergic neurons would be critical for spatial memory deficits induced by benzodiazepines and ethanol.

Animals↗

PubMed2002

Impairment of spatial memory in kaolin-induced hydrocephalic rats is associated with changes in the hippocampal cholinergic and noradrenergic contents.

We investigated the relationship between the degree of spatial memory impairment in an 8-arm radial maze and the changes in the contents of acetylcholine (ACh) and noradrenaline (NA) in the dorsal and ventral hippocampus and the frontal cortex, along with histological changes in kaolin-induced hydrocephalic rats. Kaolin-induced hydrocephalic rats were divided into three groups (non-impaired, impaired and severely impaired) according to the degree of impairment in a radial maze. Thirty percent of the hydrocephalic rats could not solve a radial maze (severely impaired group), while the remaining hydrocephalic rats could (non-impaired rats in the standard task). Forty percent of the non-impaired rats in the standard task failed to solve the delayed-response task (impaired group), whereas the remaining rats were able to solve it (non-impaired group). A positive correlation was observed between the impairment of spatial memory and ventricular dilatation. The ACh content in the dorsal and ventral hippocampus, and the NA content in the ventral hippocampus were decreased in the severely impaired group. Moreover, the NA content in the ventral hippocampus was decreased in the impaired group. These results suggest that the impairment of spatial memory in kaolin-induced hydrocephalic rats is associated with dysfunction of the hippocampal cholinergic and noradrenergic systems.

Acetylcholine↗

PubMed1985

Preservation of accurate spatial memory in aged rats.

Male rats were tested in an 8 arm radial maze from 6-26 months of age with 5 hr delay imposed between choices 4 and 5. At 26 months their spatial memory was more accurate than when they were first tested at 6 months and also more accurate than that exhibited by another 5 month old group tested concurrently. However, these old rats acquired a noval spatial habit more slowly than the younger animals. In a subsequent study, we compared the acquisition of accurate spatial memory by rats that were 3 or 21.5 months old at the start of training. Older rats adapted to the maze more slowly and required more sessions to achieve criterion with no delay imposed during the test. There was no reliable difference in acquisition when a 1 hr delay was imposed between choices 4 and 5, but the old rats learned more slowly with a 5 hr delay. On memory tests after criterion performance had been achieved, the older rats performed as well as the younger animals at all delay intervals. Aged rats are deficient in acquiring the skills required for accurate spatial memory, but once acquired these skills do not deteriorate. The possibility that other "memory" deficits associated with aging might be alleviated by overtraining is discussed.

Adaptation, Psychological↗

PubMedDate not supplied

Short-term fluctuations in elderly people's sensorimotor functioning predict text and spatial memory performance: The Macarthur Successful Aging Studies.

BACKGROUND: While age-related increases of between-person variability in a variety of cognitive measures are commonly reported in cross-sectional studies, the nature of short-term intraindividual fluctuation in elderly people's performance is relatively unexplored. OBJECTIVE: The goal of the present study is to examine short-term fluctuations in elderly people's sensorimotor functioning and their relations to individual differences in verbal and spatial memory. METHODS: Fluctuations in old adults' (mean = 75.71 years, SD = 6.93 years) sensorimotor performance were investigated by biweekly measurements spanning approximately 7 months. Sensorimotor performance was measured by three walking tasks, including the duration and the number of steps taken to walk a 360-degree circle and to walk 10 feet both at normal and fast pace. Performances of verbal and spatial memory were assessed by weekly measurements of digit memory span, memory for short text and spatial recognition. RESULTS: The magnitude of intraindividual fluctuation in most sensorimotor and memory tasks examined was at least half as great as the level of individual differences across persons. In addition, intraindividual fluctuation in sensorimotor performance is a relatively stable individual attribute, which correlates positively with age and negatively with the levels of sensorimotor, text and spatial memory performance. Although a substantial amount of individual differences in intraindividual fluctuation was shared with mean performance level, variance component and hierarchical regression analyses showed that intraindividual fluctuation in walking steps added significant independent contribution over and above that given by level of performance in predicting text and spatial memory. CONCLUSION: Taking these results together, we suggest that intraindividual fluctuations in elderly people's performance should not be ignored or simply treated as measurement error; rather, they are potentially important empirical variables for understanding sensory and cognitive aging and the nature of intraindividual response variations in general.

Aged↗

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↗