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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

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

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

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

Sex differences in spatial learning and prefrontal and parietal cortical dendritic morphology in the meadow vole, Microtus pennsylvanicus.

The prefrontal and parietal cortex has been implicated in the mediation of spatially related behaviors in male and female laboratory rats. Meadow voles, Microtus pennsylvanicus, are diurnally-crepuscularly active microtine rodents that exhibit a variety of sexually dimorphic spatially associated behaviors in both the laboratory and wild. In the present study we examined both the spatial Morris water maze performance and dendritic architecture and branching of neuronal cells in the prefrontal and parietal cortex of reproductive male and female meadow voles. Males learned the location of the hidden platform in the water task faster than estrous females and on probe trials they spent more time in the previously correct quadrant than females. Dendritic analysis with Golgi-Cox stained sections showed that male voles had significantly more dendritic arborization in the medial prefrontal and parietal cortex than females. These sex differences in both spatial navigation ability and in neural structures related to spatial navigation in meadow voles suggest that the size of neural areas might be shaped by ecological pressures associated with sexually dimorphic spatial behaviors.

Animals

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

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

Acute blockade of hippocampal glucocorticoid receptors facilitates spatial learning in rats.

Corticosteroids can facilitate or impair learning and memory processes. We found that the glucocorticoid receptor antagonist RU38486 injected locally into the dorsal hippocampus dose-dependently improved the performance of male Wistar rats in the water maze 24 h after treatment. This observation suggests a discrete specificity of hippocampal glucocorticoid receptors in facilitation of memory.

Animals

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

Stimulation of 5-HT1A receptors in the dorsal raphe reverses the impairment of spatial learning caused by intrahippocampal scopolamine in rats.

This study investigated the effect of stimulating 5-HT1A receptors in the dorsal raphe on the impairment of learning caused by 4 microg/microL scopolamine injected in the CA1 region of the dorsal hippocampus in rats performing a two-platform spatial discrimination task. At 1 (but not 0.2) microg/0.5 microL administered in the dorsal raphe on each acquisition training day 5 min before bilateral intrahippocampal injection of 4 microg/microL scopolamine, 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT), a 5-HT1A receptor agonist, had no effect on choice accuracy and latency or errors of omission but completely antagonized the impairment of choice accuracy by intrahippocampal scopolamine. Administered into the dorsal raphe at 0.2 and 1 microg/0.5 microL, WAY 100635, a 5-HT1A receptor antagonist, had no effect on rats' performance or on the impairment caused by intrahippocampal scopolamine but dose-dependently antagonized the effect of 1 microg/0.5 microL 8-OH-DPAT on the scopolamine-induced deficit. The results show that stimulation of presynaptic 5-HT1A receptors in the dorsal raphe reverses the deficit caused by intrahippocampal scopolamine, probably by facilitating the transfer of facilitatory information from the entorhinal cortex to the hippocampus. Together with a previous study showing that blockade of postsynaptic hippocampal 5-HT1A receptors antagonized the effect of intrahippocampal scopolamine in the two-platform spatial discrimination task (Carli et al., 1995b), the results suggest that drugs with presynaptic stimulatory and postsynaptic blocking actions on 5-HT1A receptors, such as partial agonists at these receptors, may be useful in the symptomatic treatment of human memory disturbances associated with loss of cholinergic innervation to the hippocampus.

8-Hydroxy-2-(di-n-propylamino)tetralin

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

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

Assessing cognitive functions in tree shrews: visuo-spatial and spatial learning in the home cage.

We developed a holeboard paradigm to investigate the cognitive abilities of tree shrews (Tupaia belangeri). The design allows animals to be tested in their homecages, which reduces possible confounding and stress factors, such as transfer to a special testing arena, food deprivation or other restraints. Nine male tree shrews performed four visuo-spatial and one spatial trial per day in two blocks of 5 consecutive days. Tree shrews needed only 1 day, that is five trials, to learn the complex holeboard paradigm. From the second day onwards the learning scores remained almost stable. To demonstrate the applicability of this paradigm in studies on the influence of stress on cognitive functions, three animals were subjected to and tested under psychosocial stress conditions on 2 consecutive days. Since the experimental animals also performed the task under stressful conditions the home cage holeboard paradigm is a valid tool to study the development of stress induced cognitive impairments.

Animals

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

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

Protein kinase C activity in the hippocampus following spatial learning tasks in mice.

Protein kinase C (PKC) is highly concentrated in the hippocampus and is thus a possible neural substrate of learning and memory. This study was designed to determine whether partial acquisition (i.e., the minimal amount of training leading to above-chance performance) of a spatial discrimination in an eight-arm radial maze alters hippocampal PKC activity. Mice were sacrificed at different times (5 minutes, 1 hour, 24 hours) after the second learning session, and PKC activity was measured in both cytosolic and membrane fractions of the hippocampus. In order to determine which component of the task was involved in the alterations in enzymatic activity, hippocampal PKC activity was also measured in a group of mice that was allowed to explore the maze freely. Significantly less PKC activity was found in the cytosolic fraction from the trained animals than from the quiet or active control groups. No differences were observed between the quiet and active controls. In contrast, there were no significant between-groups differences in membrane-bound PKC activity, although a negative correlation between the membrane-bound PKC activity and learning scores (accuracy) was noted. These results suggest that hippocampal PKC activity is involved essentially in the associative component of the task. The lack of learning-induced alterations in membrane-bound PKC activity and the negative correlation between this enzymatic activity and learning accuracy are discussed.

Animals

Enhanced disruptive spatial learning effect after sufentanil in renal hypertensive rats versus normotensive rats.

The effects of the peripherally administered sufentanil citrate (S), a potent opioid agonist with high affinity for mu receptors on the spatial navigation task, were tested in normotensive Wistar (NR) and renal hypertensive rats (RHR). Rats were injected subcutaneously once daily in doses of 0.25 or 1 microgram/kg S before the water maze training. In NR rats, weak effects of 0.25 micrograms/kg S and impairments after 1 microgram/kg S were seen, whereas in RHR 0.25 and 1 microgram/kg S showed clearcut impairments. These data from the Morris water maze task support previous reports that RHR have an increased sensitivity for opioid agonists.

Animals