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PubMed1995

Dentate gyrus destruction and spatial learning impairment after corticosteroid removal in young and middle-aged rats.

We investigated the functional and behavioral implications of chronic corticosteroid removal in young and middle-aged rats. Prepubertal and 13-month-old rats were adrenalectomized (ADX) or sham operated (SHAM). The young ADX rats were divided further into three groups: ADX with no hormone replacement, ADX given corticosterone chronically, (chCORT), and ADX given corticosterone acutely at the time of Morris water maze testing (acCORT). All rats were run on the Morris water maze 12 weeks after surgery. They were then sacrificed and the brains were removed for histological analysis. The results showed that prolonged corticosteroid absence caused major damage to the dentate gyrus and learning impairment on the Morris water maze. The chCORT rats had little dentate gyrus cell loss and were as efficient as the controls in Morris water maze performance, whereas the acCORT rats had dentate gyrus cell loss and were impaired in the spatial acquisition task. Furthermore, exogenously administered corticosterone had an interactive effect on ADX rats. Water maze performance was improved in dentate gyrus damaged rats (acCORT) compared to ADX rats not given corticosterone, whereas ADX rats with very little dentate gyrus damage (chCORT) did not exhibit better water maze performance relative to controls. Middle-aged ADX rats lost cells only in the dorsal blade of the dentate gyrus but they did not show a learning impairment in the Morris water maze relative to the middle-aged controls. These results indicate that corticosteroids are trophic for the dentate gyrus, that mature granule cells are less affected by adrenalectomy, that corticosteroid absence is responsible for some water maze impairment in ADX rats, but that in addition to corticosteroid absence, a substantial amount of dentate gyrus damage is necessary to impair spatial learning.

Adrenal Cortex Hormones↗
PubMedDate not supplied

Effect of sex and age on brain monoamines and spatial learning in rats.

The concentrations of noradrenaline (NA), dopamine (DA), serotonin (5-HT), and their metabolites were measured in the prefrontal cortex, caudate-putamen, and hippocampus in young (3 months) and aged (27-31 months) Wistar rats of both sexes. Age-related changes were found in prefrontal NA and HVA/DA ratio, striatal DA and DOPAC/DA ratio, and striatal and hippocampal 5-HT and 5-HIAA/5-HT ratio. Age and sex dependent changes were found in striatal DA and DOPAC/DA ratio, and hippocampal MHPG-SO4/NA ratio. The aged rats were tested in spatial discrimination and reversal tasks in a T maze. The effects of alpha 2-agonist medetomidine (3 micrograms/kg) on the task performance were assessed in relation to individual variation in monoamine metabolism. Medetomidine impaired spatial discrimination learning of the aged rats by interacting with the hippocampal 5-HT turnover. Medetomidine improved reversal learning through an interaction with the striatal DA turnover and reduced the number of perseverative errors after reversal, mainly due to its interaction with the prefrontal NA turnover. It is concluded that the memory enhancing effect of drugs acting through the brain monoamine systems is highly dependent on the stage of degeneration of these systems that show considerable individual variation in aged animals.

Adrenergic alpha-Agonists↗
PubMed1990

The effect of early experience on water maze spatial learning and memory in rats.

In the first of two experiments on spatial competence, groups of light-reared (LR) and dark-reared (DR) rats were compared using a "latent learning" variation of the Morris Water Maze task. On their initial test, the LR rats benefited more than DR rats did from viewing the room/pool from a platform in the correct location. Further, visually experienced rats remember the location of the platform more than DR rats when retested one month later. In a second experiment, in which a proximal cue as well as location was varied from trial to trial. LR rats again proved to be more competent than their DR counterparts. This second task also revealed significant benefits related to stimulation history in the case of a third group of animals raised in enriched or complex environment (CR) conditions. The results are discussed in terms of the nature of the impact of early experience on the ability to acquire and remember spatial concepts.

Animals↗
PubMed1996

Spatial learning in deer mice: sex differences and the effects of endogenous opioids and 60 Hz magnetic fields.

We examined the effects of brief exposure to weak 60 Hz extremely low frequency (ELF) magnetic fields and opioid systems on spatial behavior and learning in reproductive adult male and female deer mice, Peromyscus maniculatus. Sex differences were evident in spatial performance, with male deer mice displaying significantly better performance than female mice in the Morris water maze, whereby animals had to acquire and retain the location of a submerged hidden platform. Brief (maximum 5 min) exposure to weak (100 microT) 60 Hz magnetic fields during task acquisition significantly improved female performance, eliminating the sex differences in acquisition. The opiate antagonist, naltrexone, also improved female acquisition, though significantly less than the magnetic fields. These facilitatory effects involved alterations of "non-spatial" (task familiarization and reduction of related anxiety/aversive related behaviors) and possibly "spatial" aspects of the task. Enhancement of enkephalin activity with the enkephalinase inhibitor, SCH 34826, significantly reduced task performance by male deer mice. Both naltrexone and the 60 Hz magnetic fields attenuated the enkephalin mediated reductions of spatial performance. These findings indicate that brief exposure to 60 Hz magnetic fields can enhance water maze task acquisition by deer mice and suggest that these facilitatory effects on spatial performance involve alterations in opioid activity.

Analgesics↗
PubMed1991

Spatial learning of adult rats with fetal alcohol exposure: deficits are sex-dependent.

The effects of prenatal alcohol exposure on learning in adult offspring were studied in a spatial task in a T-maze. Male and female Long-Evans rats were selected from litters whose dams had received one of three treatments: alcohol in a liquid diet (35% ethanol-derived calories, 35% EDC), pair-fed nutritional control (0% ethanol-derived calories, 0% EDC) or standard control (lab chow, LC). The task included trial-independent (reference memory) and trial-dependent (working memory) components: subjects were required to make a fixed left-right discrimination, and then to alternate left and right choices to escape water. Prenatal alcohol exposure was associated with a greater number of reference errors for both sexes; only males from the alcohol prenatal treatment group, however, were impaired on the working memory component. These results suggest that prenatal exposure to alcohol can cause behavioral dysfunctions that persist into adulthood. Secondly, the pattern of memory impairments suggests that both sexes may be equivalently damaged in neural areas subserving reference memory, but that males are selectively more vulnerable in neural areas subserving working memory.

Animals↗
PubMed1995

The effects of AMPA-induced lesions of the medial septum and vertical limb nucleus of the diagonal band of Broca on spatial delayed non-matching to sample and spatial learning in the water maze.

These experiments investigated in the rat the impact on spatial delayed non-matching to sample and on acquisition of the Morris water maze of (i) AMPA-induced lesions of the medial septal nucleus, which produced a marked reduction of hippocampal choline acetyltransferase activity and acetylcholine levels (measured using in vivo dialysis) together with lesser reductions in cholinergic markers in the cingulate cortex and (ii) similar AMPA-induced lesions of the vertical limb nucleus of the diagonal band of Broca (vDB), which produced more marked reductions in cholinergic markers in the cingulate cortex than in the hippocampus. Medial septal lesions produced a delay-dependent deficit in spatial working memory, while lesions of the vDB resulted in a delay-independent performance deficit. In addition, rats with vDB lesions adopted biased response strategies during the imposition of long delays. Neither lesion significantly affected the acquisition of a spatial reference memory task, the Morris water maze. The results are discussed in terms of cholinergic- and GABAergic-dependent functions of the hippocampal formation and cingulate cortex in spatial short-term and reference memory.

Acetylcholine↗
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↗
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↗
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↗