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PubMed1991

Effect of exposure to high pressure on subsequent spatial learning and memory in rats.

The effects of high helium pressure on the subsequent acquisition of spatial memory were studied in male rats. Thirty-two rats were exposed to 65 ATA helium-oxygen pressure for 4.2 days, decompressed (total time in chamber 5 days), and then tested in an eight-arm radial maze. Thirty-two control rats were exposed in the chamber to 1 ATA air. Each rat had 20 sessions in the maze (2 sessions/day for 10 days), and the number of correct (visiting an arm not previously visited to obtain the reward pellet) and incorrect choices (visiting a previously visited arm) were recorded. Statistical analysis showed that the rats exposed to 65 ATA performed significantly better than 1-ATA controls during the first 8 of 20 sessions. This effect was most pronounced in sessions 5-8. Results for sessions 9-20 showed that the pressure-treated rats still made more correct choices but to an extent that did not always reach statistical significance. Possible explanations include the pressure-treated rats performing better because of hunger after a lower food consumption at pressure. Alternatively, pressure itself may enhance proposed mechanisms of spatial memory such as long-term potentiation.

Animals↗
PubMed1987

Exploration and spatial learning in staggerer mutant mice.

Staggerer mutant mice, that lose cerebellar Purkinje cells and granule cells and inferior olive neurons, were evaluated in tests of spontaneous alternation and maze learning. It was found that, contrary to normal mice, the staggerer mutants did not alternate spontaneously and had deficits in the acquisition of maze learning. It is hypothesized that the olivocerebellar system has a role in visuo-spatial organization.

Animals↗
PubMed1997

Spatial learning activates neural cell adhesion molecule polysialylation in a corticohippocampal pathway within the medial temporal lobe.

Transient and time-dependent modulations of neural cell adhesion molecule (NCAM) polysialylation in the dentate gyrus of the rodent hippocampus are a feature of spatial and nonspatial forms of learning. In the hippocampal formation, polysialic acid immunoreactivity was localized to granule-like cells and their mossy fibre axons. We now demonstrate the latter to extend to the CA3 region where apparent recurrent and Schaffer collaterals were labelled. The axons of the CA1 pyramidal cell layer were immunopositive, as was the subiculum that they innervate. Layers I and III of the entorhinal cortex stained intensely for polysialic acid; however, these were not visible in the more lateral aspect of this region and were replaced by a single band of immunopositive neurons that extended to include the perirhinal and piriform cortices. After Morris water maze training, the number of polysialylated neurons within the entorhinal cortex exhibited a two- to threefold increase at the 10-12-h posttraining time with respect to that observed immediately after training. This increase was task specific, as no change was observed in freely swimming animals or those required to locate a visible platform. These results suggest the presence of a corticohippocampal pathway involved in the eventual consolidation of memory.

Age Factors↗
PubMed1984

Effects of gender and alcoholism on verbal and visual-spatial learning.

Sex differences in cognitive abilities of chronic alcoholics were investigated using a paired-associates learning test with separate but similarly structured verbal and visual-spatial components. Four groups of 35 subjects each, equated for age and education, were tested: male and female alcoholics, and male and female community control subjects. As expected, sex differences were found on the component tasks: overall, nonalcoholic women performed significantly better than nonalcoholic men on the verbal measure, and nonalcoholic men performed better than nonalcoholic women on the visual-spatial measure. Nonalcoholic men had a larger discrepancy between component scores than nonalcoholic women, suggesting greater lateralization of cognitive functions; however, this difference did not reach significance. The effects of alcoholism were different for the sexes. Alcoholic women were not impaired on either the verbal or visual-spatial measure, but the alcoholic men demonstrated deficits in visual-spatial performance. In addition, they showed less difference between verbal and visual-spatial component scores than the other groups, suggesting that alcoholism attenuated the effects of hemispheric specialization for cognitive abilities normally found in men.

Adult↗
PubMed1993

Severity of spatial learning impairment in aging: development of a learning index for performance in the Morris water maze.

The Morris water maze task was originally designed to assess the rat's ability to learn to navigate to a specific location in a relatively large spatial environment. This article describes new measures that provide information about the spatial distribution of the rat's search during both training and probe trial performance. The basic new measure optimizes the use of computer tracking to identify the rat's position with respect to the target location. This proximity measure was found to be highly sensitive to age-related impairment in an assessment of young and aged male Long-Evans rats. Also described is the development of a learning index that provides a continuous, graded measure of the severity of age-related impairment in the task. An index of this type should be useful in correlational analyses with other neurobiological or behavioral measures for the study of individual differences in functional/biological decline in aging.

Aging↗
PubMed1996

Basolateral amygdala lesions block glucocorticoid-induced modulation of memory for spatial learning.

This study examined the role of the amygdala in mediating the effects of glucocorticoids on spatial memory in rats. Adrenalectomy (ADX) induced 4-5 days prior to training impaired memory in a water-maze spatial task. This effect was reversed by a posttraining injection of dexamethasone (0.3 mg/kg sc) but not by corticosterone (0.3 mg/kg). Lesions of the basolateral (BLA), but not the central (CEA) or the medial (MEA), amygdala blocked the effects of ADX and dexamethasone. ADX also impaired acquisition. CEA, MEA, and BLA lesions blocked the ADX effect on acquisition. In adrenally intact rats, intracerebroventricular posttraining injections of a specific glucocorticoid receptor (GR or Type-II) antagonist impaired retention, and BLA lesions blocked the effect of the GR antagonist. These findings provide evidence that the BLA is involved in mediating glucocorticoid influences on learning and memory.

Adrenalectomy↗
PubMed1994

Reversible inactivation of the lateral dorsal thalamus disrupts hippocampal place representation and impairs spatial learning.

Place-specific discharge of hippocampal cells was monitored while rats performed daily 15 trials of a spatial memory task. During the intertrial interval between trials 5 and 6, the lateral dorsal nucleus of the thalamus (LDN) was reversibly inactivated. Choice accuracy on the maze became impaired, and many hippocampal place fields became disrupted. These data support the proposition that the LDN passes onto hippocampus important (spatial) information that is used for accurate maze navigation.

Animals↗
PubMed1985

Spatial learning disabilities and underachievement among university anatomy students.

In this study the relationship between underachievement in anatomy and spatial ability (both geometrical and anatomical) is investigated. Subjects were second-year medical students at the University of Cape Town from 1980 to 1983. Geometrical spatial ability was measured using a battery of three-dimensional exercises involving the sectioning, joining, translation, rotation and visualization of simple solid objects. Anatomical spatial achievement was measured using university practical examination scores of April, June and October, as well as students' scores on those items in the April, June and November MCQ anatomy examinations which were classified as spatially three-dimensional by a panel of lecturers in anatomy. Non-spatial anatomical achievement was measured using the university essay examination scores of April, June and November, together with students' scores on the non-spatial items in the MCQ anatomy examinations. From 1980 to 1983 it was found that students who failed the battery of geometrical spatial exercises and/or recorded large, persistent deficits on spatial MCQs relative to non-spatial MCQs, scored significantly lower marks in practical anatomy examinations throughout the year than those students who scored well in the battery of geometrical spatial exercises. Spatially competent and spatially inept students performed equally well on the non-spatial MCQs and the non-spatial essay examinations. Borderline and failing students recorded the greatest deficits in anatomical spatial scores (for whom losses of approximately 18% occurred in practical examinations in anatomy). Since potential failures with persistent spatial handicaps can be readily identified by mid-year, a programme of differentiated teaching methods is recommended for these students.

Achievement↗
PubMed1984

Learning spatial dimensions with a visual sensory aid: Molyneux revisited.

The relationship between sensory aid research and several areas of perceptual learning has been explored with five experiments on learning the use of the Binaural Sensory Aid, an electronic sensor in which pitch specifies distance and interaural amplitude difference (IAD) specifies direction. The training task required reaching to objects in near space, with tactile error feedback. Perceptual learning for both dimensions was demonstrated within 72 trials, giving a level of performance comparable to the use of a natural sound source, although performance with the direction cue did not reach asymptote until a second training session. Training was unaffected by various kinds of regularity in the spatial target sequences, or by a reduction in the number of spatial target locations until only two locations were used; at this point directional accuracy declines. Training only one dimension at a time did not produce additional improvement of performance on that dimension, but did impair generalization of the direction cue. Learning of the pitch-distance dimension was generally better than that of the IAD dimension, possibly because of its greater discriminability with this device. Generally, the pattern of results indicates that in learning to use such devices subjects readily determine the sensory dimensions of the codes and have considerable ability to generalize to new locations.

Distance Perception↗
PubMed1994

The effect of electroconvulsive shock and nifedipine on spatial learning and memory in rats.

Several traumatic events including brain contusion, electroconvulsive shock therapy, epileptic seizures and others, may cause short-term retrograde amnesia. In spite of much recent attention, pharmacological treatment of memory impairment has not been fully successful. In the present paper we report on the possible antiamnesic action of the L-type calcium channel blocker, nifedipine. Rats trained in the spatial memory task showed gradual improvement in the escape latency to find the submerged platform. After completion of the learning, they also showed a strong spatial bias toward the place that previously contained the target platform. Prolonged post-trial electroconvulsive shock induced memory impairment. The calcium channel blocker, previously reported as a "cognitive enhancer," given either before or after the learning trial revealed no antiamnesic effect. Nifedipine also does not exert any action when given alone. These results suggest that the drug may not have antiamnesic action on human memory disturbed by electroconvulsive therapy.

Animals↗
PubMed1997

Learning spatial sequences in unilateral neglect.

Brain-damaged patients with unilateral spatial neglect ignore aspects of the world located on the side opposite their lesion. In the present study we examined the performance of unilateral neglect patients (UN) on an SRT task in which a hybrid repeating sequence (21313) was used. We analyzed the patients' performance for each location separately as a function of the target's location in the trial preceding the response. The UN patients were severely limited in their learning of the sequence when compared to normal controls. In particular, they appeared to learn unique associations (21 and 13) but not ambiguous ones (31 and 32). We discuss two possible explanations for this phenomenon. The first is that UN patients show a deficit similar to that of normal subjects in dual task situations. The second is that the learning deficit is unique to spatial processing impairments of UN patients and is not directly related to research with normal population. We outline future research that may distinguish between these two explanations.

Attention↗
PubMed1994

Naloxone facilitates spatial learning in a water-maze task in female, but not male, adult nonbreeding meadow voles.

The present study examined the effects of the opiate antagonist naloxone on spatial acquisition and retention in a water-maze task by adult, nonbreeding, male and female meadow voles (Microtus pennsylvanicus). Voles were required to learn the position of a hidden, submerged platform using distal visual cues. There were four trials per day for 6 days. Daily pretraining (15 min before first trial) systemic administrations of naloxone (1.0 mg/kg, IP) significantly facilitated spatial acquisition in female, but not in male, voles in a water-maze task on days 2, 3, and 4. There were two probe tasks given 1 day and 1 week after the last training trial. All groups acquired the spatial task by the end of the fifth day with no significant effects of naloxone on retention of the spatial task. There were also no significant sex differences in acquisition of the spatial task and task retention in control, nonbreeding adult voles. It is suggested that the lack of sex differences in basal spatial performance may be related to the low levels of testosterone in male nonbreeding voles. The obtained sex differences in the effects of naloxone on spatial acquisition are considered in relation to sex differences in stress, opiate responses, and gonadal steroid levels.

Animals↗
PubMed1988

Rotational stimulation disrupts spatial learning in fornix-lesioned rats.

Normal and fornix-lesioned rats were trained to find water in a version of a spatial discrimination task involving the use of a cross maze modified for interspersing rotational stimulation before the start of each trial. The central (cross) portion of the maze rested on a turntable and consisted of a covered start box opening into the intersection of the cross, allowing choice among three covered alleys, each of which led through a black curtain onto a stationary goal arm. The animal could be started in one of three positions (0 degree, 90 degrees, 270 degrees) in relation to the rewarded goal arm. Room cues were not available until after the animal made the choice in the covered tunnel area. A 20-day testing period in which one to ten full revolutions were interspersed before the start of each trial revealed marked differences between normal and fornix-lesioned animals. The overall performance of normal animals improved from 40% correct choices to 85% correct during the testing period. Fornix-lesioned rats showed no significant improvement during the same period. Performance on probe trials in which room cues were made available to the animals during interspersed rotations improved rapidly and was not significantly different between the two groups. The results suggest that adaptation to vestibular system stimulation was required to solve the covered tunnel task in normal rats and that such processes were disrupted in fornix-lesioned rats.

Animals↗
PubMed1989

Enhanced detection of nucleus basalis magnocellularis lesion-induced spatial learning deficit in rats by modification of training regimen.

Bilateral excitotoxic lesions of the nucleus basalis magnocellularis (NBM) in the rat cause deficits in the water maze, a spatial memory paradigm. Previous investigations aimed at reversing the water maze performance deficit with anticholinesterase treatments have been unable to demonstrate a consistent drug effect due to the relatively good acquisition of the task seen following NBM lesions. The present investigation tested three different water maze training regimens designed to separate the learning curves. F-344 rats received bilateral NBM injections of ibotenic acid; sham-operated rats served as controls. The animals were tested in three groups in the water maze as follows: (1) four trials per day with no intertrial interval (standard paradigm), (2) four trials per day with a 10-minute intertrial interval, and (3) two trials per day with no intertrial interval. Each group was tested in the water maze for five consecutive days, followed by two days of rest, and then tested for an additional five days. The two-trial per day paradigm was more difficult than the standard paradigm for both lesions and controls and yielded the most difference between lesions and controls as compared to the other two testing regimens. The 10-min intertrial interval schedule was more difficult than the standard paradigm for lesioned animals but acquisition was not affected in control rats. These data demonstrate that the nucleus basalis lesions cause a deficit in the water maze task regardless of training parameters. Further, while all rats showed some acquisition of the water maze task, training schedule affected the level of learning of both lesioned and control rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1997

Object-recognition and spatial learning and memory in rats prenatally exposed to ethanol.

Prenatal ethanol exposure can produce cognitive and behavioral impairments. In the present study, rats from prenatal ethanol (E), pair-fed (PF), and ad libitum-fed control (C) treatment conditions were tested on the object-recognition delayed-nonmatching-to-sample (DNMS) task with nonrecurring items and on the spatial-navigation Morris water maze task. In Experiment 1, there were no significant differences among groups in object-recognition learning and memory, distractibility, or response perseveration on the DNMS task. In Experiment 2, the same rats were tested in the water maze; E rats took significantly longer to learn the task than did the PF or C rats. These data suggest that the mechanisms underlying spatial cognitive abilities are more vulnerable to the teratogenic effects of prenatal ethanol exposure than those underlying object-recognition abilities.

Animals↗
PubMed1989

The effects of undernutrition during early life on spatial learning.

Recent research has shown that a lengthy period of undernutrition during early postnatal life can cause alterations in the morphological structure of the dentate gyrus. As this region is involved in the control of spatial memory, we decided to investigate whether undernourished rats also showed any deficits in this aspect of behaviour. Rats were undernourished from about birth until either 30 or 60 days of age and then nutritionally rehabilitated for a lengthy period before testing. There were significant differences in the body weight of control and undernourished rats in each experiment. The testing procedure involved rats being placed in a large pool of opaque water. They were required to swim to find a hidden platform located just below the water surface onto which they could escape. Each rat had to perform this test 20 times over a period of 3 days. The time taken and the total distance swum by each rat during each trial was measured. In Experiment 1, rats were familiarised with the water before testing took place, whereas in Experiment 2 they were not. There were no significant differences in the latency to find the platform or the distance swum between well-fed control and previously undernourished rats in either experiment. In conclusion, in our experiments we could not demonstrate that undernutrition during early life caused any deficits in spatial memory performance.

Animals↗
PubMed1995

Phencyclidine injections into the dorsal hippocampus disrupt long- but not short-term memory within a spatial learning task.

Since the hippocampus is likely to be a major site of phencyclidine (PCP) action, the effects of various doses of PCP (1.8, 18 or 36 nM) as well as 3.6 nM MK-801 or saline injected directly into the dentate gyrus of the hippocampus was tested for acquisition of a spatial navigation task (dry land version of a water maze) using a paradigm that assesses short term memory based on learning within a day and long term memory based on learning between days. Results indicated that relative to saline or 1.8 nM PCP injected rats, rats with 18 or 36 nM PCP or 3.6 nM MK-801 injections were impaired in acquisition of the task as measured by increased distances traveled to find the food location between days but not within days. In additional experiments 36 nM PCP or 3.6 nM MK-801 did not produce any deficits in the acquisition of an object discrimination task. It is suggested that PCP through its blocking action of the NMDA receptor in the dentate gyrus or CA1 region of the dorsal hippocampus mediates the consolidation of new spatial location information.

Animals↗