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At least 127 records · Page 7Linked to original sources
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↗
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↗
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↗
PubMed1982

Cortical noradrenaline depletion eliminates sparing of spatial learning after neonatal frontal cortex damage in the rat.

The possibility that cortical noradrenaline (NA) is necessary for the sparing of function that occurs after neonatal frontal cortex damage was examined. Spatial localization by rats with frontal cortex damage sustained neonatally was better than by rats with similar damage sustained as adults. The sparing was abolished in rats depleted of cortical noradrenaline by means of neonatal 6-hydroxydopamine (6-OHDA) administration. NA depletion alone did not affect spatial localization. These data are consistent with the notion that NA has some general function in maintaining some forms of plasticity in posterior cortex.

Animals↗
PubMed1992

D-cycloserine reverses the working memory impairment of hippocampal-lesioned rats in a spatial learning task.

It is shown that D-cycloserine has cognition-enhancing properties in quinolinic acid hippocampal-lesioned rats. Lesioned rats had a severe impairment of working memory in an allocentric spatial reversal paradigm in the 8-arm maze, and performance could be restored with 12 mg/kg i.p. D-cycloserine, given 30 min before testing. The present findings favour the testing of D-cycloserine for clinical efficacy in patients with Alzheimer's disease with loss of pyramidal neurons and disconnected glycine-NMDA receptor activation.

Analysis of Variance↗
PubMed1992

8-Hydroxy-2-(di-n-propylamino)tetralin impairs spatial learning in a water maze: role of postsynaptic 5-HT1A receptors.

1. The effects of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), a 5-HT1A receptor agonist, on place navigation was studied by use of two spatial tasks in a water maze. 2. In the first experiment, rats treated subcutaneously with 100 and 300 (but not 30) micrograms kg-1 8-OH-DPAT were impaired in their ability to locate a hidden platform. The probe test confirmed the impairment of spatial navigation but the effect (time spent in the training quadrant) was quantitatively different, depending on whether 8-OH-DPAT was administered only before each training session, only before the probe test or in both conditions. 3. In the second experiment, rats received 150 micrograms 5,7-dihydroxytryptamine (5,7-DHT) intracerebroventricularly to destroy 5-hydroxytryptamine (5-HT)-containing neurones and 24 days later were examined for choice accuracy in a two-platform spatial discrimination task. 4. At 100 (but not 30) micrograms kg-1 8-OH-DPAT impaired rats' accuracy with no effect on latency and no errors of omission. In 5,7-DHT-treated rats, this dose had a greater effect, including errors of omission. Sham-operated rats injected with 300 micrograms kg-1 8-OH-DPAT were markedly impaired in accuracy but they had longer latencies and made more errors than controls. All the effects were increased in 5,7-DHT treated rats. 5. The results suggest that, at doses causing no apparent changes in motor behaviour or motivation, 8-OH-DPAT impairs spatial navigation by stimulating postsynaptic 5-HT1A receptors in the rat brain.

5,7-Dihydroxytryptamine↗
PubMed1994

Perinatal undernutrition impairs spatial learning in recovered adult rats.

Learning ability of adult rats undernourished at perinatal age and nutritionally recovered (D-rats) was assayed in the Morris water maze test as compared with controls (C-rats). D-rats showed longer escape latencies to locate a hidden platform in absence of proximal cues during the acquisition period. Swimming pre-training experience did not improve this shortcoming. Retention scores obtained 1, 3, 10 and 30 days after training showed that spatial information was efficiently consolidated after acquisition since D-rats performed as well as C-rats on retention tests. A cue learning task revealed no significant differences between both groups. These results suggest that perinatal undernutrition induces, even after a long period of nutritional recovery, a deficit in efficient place navigation in adult rats.

Analysis of Variance↗
PubMed1992

Competitive and non-competitive NMDA receptor antagonists in spatial learning tasks.

The effects of the competitive N-methyl-D-aspartate (NMDA) receptor antagonists, CGP37849 (3 or 6 mg/kg i.p.) and its ethyl ester CGP39551 (5 or 15 mg/kg i.p.) and of the non-competitive NMDA receptor antagonist, dizocilpine (0.16 mg/kg; i.p.) on acquisition by rats of different spatial orientation tasks in an 8-arm radial maze were evaluated. Neither of the CGP compounds influenced locomotor activity during spontaneous alternation, only dizocilpine increased the number of arm entries (locomotion). Preferred angles between consecutive arm entries were changed by the high doses of CGP37849 (6 mg/kg), CGP39551 (15 mg/kg) and dizocilpine (0.16 mg/kg). The high doses of both CGP compounds as well as dizocilpine produced impairments in the acquisition of an egocentric orientation task and an allocentric reversal task indicated by an increased number of arm entries and re-entries. Such amnesic effects did not occur after administration of low doses of CGP37849 (3 mg/kg) and CGP39551 (5 mg/kg), doses which are sufficient to produce anticonvulsant and anticataleptic effects. In contrast, the non-competitive NMDA receptor antagonist, dizocilpine, produced amnesic effects over the entire behaviourally effective dose range.

2-Amino-5-phosphonovalerate↗
PubMed1985

Spatial learning and memory, maze running strategies and cholinergic mechanisms in two inbred strains of mice.

The acquisition process of the radial maze task was studied in two inbred strains of mice, C57BL/6 and DBA/2. A quantitative and qualitative evaluation of performance was performed and the pretest level of activity was measured. The results showed a significant correlation between activity and performance since the highly active C57BL/6 mice exhibited better performance of the radial maze task than the less active DBA/2 mice. Moreover, for correct trials, strain-dependent maze-running strategies were observed: while both strains displayed about the same percentage of clockwise and spatial strategies, it was observed that among the spatial strategies C57BL/6 used a larger number of different correct solutions. Subsequently, the effect of scopolamine administration on working memory processes was assessed in sequential and discrete trials. A different reactivity of each strain to anti-cholinergic treatment was found in discrete trials since only DBA/2 mice were impaired. The effect of scopolamine is discussed in relation to the different models of information processing involved in learning and memorizing the experimental rule.

Animals↗
PubMed1995

Glucocorticoids, hippocampal corticosteroid receptor gene expression and antidepressant treatment: relationship with spatial learning in young and aged rats.

The emergence of cognitive deficits in a subgroup of aged rats is associated with increased hypothalamic-pituitary-adrenal axis activity, decreased hippocampal mineralocorticoid and/or glucocorticoid receptor gene expression and neuronal loss. Short-term treatment with antidepressant drugs in young rats increases hippocampal corticosteroid receptor gene expression. In this study, the effects of chronic antidepressant administration on hippocampal mineralocorticoid and glucocorticoid receptor gene expression and spatial memory in young and aged rats were investigated. Young (eight months) and old (22 +/- 1 months) Lister-hooded rats were ranked according to watermaze performance. Matched pairs of rats were treated with amitriptyline (10 mg/kg) or saline daily for nine weeks, then reassessed in the watermaze. Amitriptyline significantly improved spatial memory in the young rats (33% increase in transfer test time) and increased hippocampal mineralocorticoid, but not glucocorticoid receptor messenger RNA expression. By contrast, in aged rats, amitriptyline had no effect on spatial memory or hippocampal corticosteroid receptor gene expression, either in cognitively unimpaired or cognitively-impaired animals. In aged rats, basal plasma corticosterone levels, which were significantly higher than in young animals, correlated negatively with spatial memory, while hippocampal glucocorticoid receptor mRNA expression correlated negatively with plasma corticosterone levels and positively with spatial memory. Amitriptyline had no significant effect on basal morning plasma corticosterone levels in either young or aged rats, but significantly decreased evening corticosterone levels in aged rats. Our data support the notion that corticosterone exerts a concentration-dependent biphasic influence, via selective activation of hippocampal mineralocorticoid and glucocorticoid receptor, on spatial memory. Amitriptyline improves spatial memory in young rats and increases hippocampal mineralocorticoid receptor gene expression. The lack of amitriptyline effect on spatial memory in aged rats may reflect decreased plasticity of both the synaptic processes underlying spatial memory and the regulation of hippocampal mineralocorticoid/glucocorticoid receptor expression, with mineralocorticoid receptors fully occupied due to elevated basal plasma corticosterone levels (in part a consequence of inadequate glucocorticoid receptor function).

Aging↗
PubMed1989

Transplantation of septal cholinergic neurons to the hippocampus improves memory impairments of spatial learning in rats treated with AF64A.

Embryonic septal neurons were transplanted into damaged hippocampus in adult rats which had received lateral ventricular administration of AF64A, a cholinergic neurotoxin. About 3 months after transplantation, the rats with bilateral septal grafts showed significant improvement in the radial maze and T-maze tasks. Many ingrowths of acetylcholinesterase (AChE)-positive fibers originating from the grafts were observed in the hippocampus of the rats which showed good performance in these learning tasks. These results indicate that transplantation of septal cholinergic neurons into the AF64A-treated hippocampus may induce at least partial recovery in learning tasks believed to involve the hippocampus.

Animals↗
PubMed1990

Spatial learning is affected by transient occlusion of common carotid arteries (2VO): comparison of behavioural and histopathological changes after '2VO' and 'four-vessel-occlusion' in rats.

Place learning in the Morris water maze following transient (24 min) occlusion of the common carotid arteries (2VO), and following permanent occlusion of both vertebral arteries plus transient (20 min) clamping of the carotids (4VO) was investigated in rats 6-9 days after occlusion. Both 2VO and 4VO treatment increased the latency to find the hidden platform during escape trials; spatial bias, tested in a probe trial, was decreased. Histological analysis revealed neural necrosis in the CA1 sector of the hippocampus in 4VO rats but not in 2VO animals. The data suggest that an experimentally induced reduction in cerebral blood flow of 50% (after 2VO) or 95% (after 4VO) produces persistent functional changes even in absence of actual neural damage.

Animals↗
PubMed1989

Spatial learning in rats: correlation with cortical choline acetyltransferase and improvement with NGF following NBM damage.

Rats display an acquisition deficit in a circular water maze following excitotoxic lesions of the nucleus basalis magnocellularis (NBM). Experiments were therefore performed to determine if acquisition behavior on this task could predict the degree of cortical cholinergic deafferentation and if the acquisition deficit could be pharmacologically reversed. Performance on acquisition was highly correlated with the lesion-induced reduction in cortical choline acetyltransferase (ChAT) activity. Accuracy of spatial behavior was highly correlated to percentage ChAT depletion (r = 0.75). Neither lesioned rats nor controls displayed a retention deficit after a 9-day interval, nor did either group display a passive-avoidance retention deficit. To test the causal relationship between cholinergic dysfunction and spatial behavior, the central nervous system cholinergic enhancer nerve growth factor (NGF) was intraventricularly infused for 4 weeks. NGF infusion resulted in improved acquisition of the water maze task compared to NBM-lesioned rats receiving vehicle infusion and untreated rats with NBM lesions. These studies indicate that the decrease in cortical ChAT activity is likely to be responsible for the observed acquisition deficit and that pharmacological manipulations can be successfully used to improve behavior following NBM lesions.

Animals↗
PubMed1985

Facilitation of spontaneous and learned spatial behaviours following 6-hydroxydopamine lesions of the lateral septum: a cholinergic hypothesis.

Mice received injections of 6-hydroxydopamine (6-OHDA) in the lateral septum; they were tested for spontaneous alternation, acquisition and reversal of a spatial discrimination in a T-maze. In each of these tasks, performance of 6-OHDA lesioned mice was improved relative to controls. Neurochemical analysis revealed that 6-OHDA lesioned mice exhibited a significant increase in the rate of sodium-dependent high affinity choline uptake in the hippocampus. These results are discussed in relation to current theories concerning the role of the septo-hippocampal complex and cholinergic system in the control of behaviour.

Animals↗
PubMed1992

Parenteral domoic acid impairs spatial learning in mice.

The present study is the first to examine the effect of a single intraperitoneal injection of the neuroexcitotoxin domoic acid on learning in mice. Compared to saline controls, animals exposed to domoic acid (2.0 mg/kg) showed significant impairment on the acquisition of the place task in the Morris water maze. Observation of swim paths taken by mice searching for the underwater platform revealed a failure on the part of the domoic acid-exposed mice to select the appropriate problem solving strategies. The results, along with neuroanatomic work done here and elsewhere, suggest that impairment of acquisition and retention of this spatial navigation task by domoic acid, involves a neuropathology that includes not only the hippocampus, but other limbic, and possibly extralimbic brain regions.

Animals↗