Conditioning of gray crows (Corvus cornix L.) in a "giant" eight-arm radial maze

Twelve adult hooded crows (Corvus cornix) were trained to perform a standard radial-maze task in a giant eight-arm outdoor radial maze constructed at the "Chistyi les" Biological Station (Tver oblast) for comparative investigations of spatial memory in birds and mammals. The maze consists of a central part of 250 cm diameter, and has arms of 650 cm length, 170 cm height and 80 cm width. The examined hooded crows showed good task performance. Errors (repeated visits to empty arms) were few in number and were predominantly connected with the tendency to avoid arms close to an observer.     

Effects of the NMDA antagonist MK-801 on radial maze performance in histidine-deficient rats

We examined the effects of a histidine-deficient diet on brain histamine contents as well as on learning and memory using the eight-arm radial maze in rats. A significant decrease in histamine content in the hippocampus was observed after long-term feeding of rats with a histidine-deficient diet. At the same time, significant enhancement of the acquisition process in radial maze performance was also observed. Pyrilamine did not show a significant effect on radial maze performance in histidine-deficient rats. On the other hand, pyrilamine caused a significant spatial memory deficit in control rats. Scopolamine was effective in inhibiting spatial memory in both histidine-deficient and control rats. MK-801 caused spatial memory deficits more potently in histidine-deficient rats than in controls. Brain glycine contents showed a significant increase in the hippocampus in histidine-deficient rats. These results indicated that the spatial memory deficits induced by MK-801 in histidine-deficient rats are closely related to increased glycine levels and activation of NMDA receptors.     

Tool Use Specific Adult Neurogenesis and Synaptogenesis in Rodent (Octodon degus) Hippocampus

We previously demonstrated that degus (Octodon degus), which are a species of small caviomorph rodents, could be trained to use a T-shaped rake as a hand tool to expand accessible spaces. To elucidate the neurobiological underpinnings of this higher brain function, we compared this tool use learning task with a simple spatial (radial maze) memory task and investigated the changes that were induced in the hippocampal neural circuits known to subserve spatial perception and learning. With the exposure to an enriched environment in home cage, adult neurogenesis in the dentate gyrus of the hippocampus was augmented by tool use learning, but not radial maze learning, when compared to control conditions. Furthermore, the proportion of new synapses formed in the CA3 region of the hippocampus, the target area for projections of mossy fiber axons emanating from newborn neurons, was specifically increased by tool use learning. Thus, active tool use behavior by rodents, learned through multiple training sessions, requires the hippocampus to generate more novel neurons and synapses than spatial information processing in radial maze learning.     

Effects of testosterone on spatial learning and memory in adult male rats

A male advantage over females for spatial tasks has been well documented in both humans and rodents, but it remains unclear how the activational effects of testosterone influence spatial ability in males. In a series of experiments, we tested how injections of testosterone influenced the spatial working and reference memory of castrated male rats. In the eight-arm radial maze, testosterone injections (0.500 mg/rat) reduced the number of working memory errors during the early blocks of testing but had no effect on the number of reference memory errors relative to the castrated control group. In a reference memory version of the Morris water maze, injections of a wide range of testosterone doses (0.0625-1.000 mg/rat) reduced path lengths to the hidden platform, indicative of improved spatial learning. This improved learning was independent of testosterone dose, with all treatment groups showing better performance than the castrated control males. Furthermore, this effect was only observed when rats were given testosterone injections starting 7 days prior to water maze testing and not when injections were given only on the testing days. We also observed that certain doses of testosterone (0.250 and 1.000 mg/rat) increased perseverative behavior in a reversal-learning task. Finally, testosterone did not have a clear effect on spatial working memory in the Morris water maze, although intermediate doses seemed to optimize performance. Overall, the results indicate that testosterone can have positive activational effects on spatial learning and memory, but the duration of testosterone replacement and the nature of the spatial task modify these effects.     

Spatial learning deficit in the rat after exposure to a 60 Hz magnetic field

Rats were trained in ten daily sessions to perform in a 12-arm radial maze, which is a behavioral test for spatial memory functions. Exposure to a 60 Hz magnetic field (45 min, 0.75 mT) immediately before each training session retarded learning significantly. Pretreatment with the cholinergic agonist physostigmine before magnetic field exposure reversed the field's effect on spatial learning. Data from this experiment indicate that magnetic field-induced spatial learning deficit is caused by the effect of the field on cholinergic systems. © 1996 Wiley-Liss, Inc.     

Development of a maze test and its application to assess spatial learning and memory in Merino sheep

A maze test was developed to assess spatial memory and learning in Merino sheep. Total time to traverse the maze and times spent in cul de sacs (errors) were used to assess performance. Both total time and errors decreased when the performance of sheep was assessed on three consecutive days, indicating that sheep learnt to traverse the maze. Scopolamine hydrobromide, a drug known to impair memory, was administered to sheep to validate whether the maze could be used to assess deficits in learning and spatial memory. Sheep receiving scopolamine hydrobromide 30 min before maze testing on each of three successive days were significantly slower to complete the maze on day 3 compared to control sheep receiving saline. The results suggested that the maze was measuring spatial memory and therefore might be useful to assess neurological deficits related to spatial memory and learning in sheep in neurological conditions such as Annual Ryegrass Toxicity. Tunicamycins are chemically and toxicologically analogous to the corynetoxins that cause the often fatal neurological disease Annual Ryegrass Toxicity. Exposure to tunicamycins did not affect total time to complete the maze, the number of errors committed or the ability to retain the memory of the maze configuration when tested 6 weeks later. These results, in addition to showing no adverse effect of the tunicamycins, also indicate that sheep have the ability to learn and retain the spatial memory of a relatively complex maze.     

Preventive action of Ginkgo biloba in stress- and corticosterone-induced impairment of spatial memory in rats

In this study, we tested preventive effects of a natural medicine the extract of Ginkgo biloba (EGB 761) on post-stress cognitive dysfunction. Exposure to chronic restraint stress in rats and psychosocial stress in humans has been shown to alter cognitive functions such as learning and memory and have been linked to the pathophysiology of mood and anxiety disorders.Our findings indicate that chronic restraint stress impaired egocentric spatial memory as observed in the eight-arm radial maze but it did not alter the allocentric spatial memory in the Morris water maze. In control rats EGB 761 (100 mg/kg, orally) improved spatial memory in these two tests. Also, EGB 761 normalized cognitive deficits seen in rats chronically stressed or treated with an ‘equivalent’ dose of exogenous corticosterone (5 mg/kg, subcutaneously).We conclude that, in rats, repeated administration of EGB 761 prevents stress- and corticosterone-induced impairments of spatial memory.     

Does Seed‐Caching Experience Affect Spatial Memory Performance by Pinyon Jays?

Food‐storing birds use spatial memory to find previously cached food items. Throughout winter, pinyon jays (Gymnorhinus cyanocephalus) rely heavily on cached pinyon pine (Pinus edulis) seeds. Because of a recent severe drought, pinyon pine trees had not produced a significant seed crop for several years. Therefore, 1‐ and 2‐yr‐old birds never had the opportunity to cache and recover seeds and birds 4 or more years of age had not recovered seeds in 3 yr. This study examined whether natural but extreme variability in experience might result in differences in abstract spatial memory ability during a non‐cache recovery test of spatial memory. Three groups of jays were tested for spatial memory ability in an open room analog of the radial arm maze. Two of the groups were 8 mo old: young/minimally experienced birds which had 2 mo of experience in the wild, while young/experienced birds had 5 mo of experience in their natural habitat. The third group, adult, consisted of birds more than 3 yr old, with at least 3 yr of experience in their natural habitat. This was the only group with experience caching pine seeds. All three groups performed equally and well above chance. This suggests that spatial memory is fully developed by 8 mo of age and is not affected by extensive experience in the wild.     

Does Chronic Unpredictable Stress during Adolescence Affect Spatial Cognition in Adulthood?

Spatial abilities allow animals to retain and cognitively manipulate information about their spatial environment and are dependent upon neural structures that mature during adolescence. Exposure to stress in adolescence is thought to disrupt neural maturation, possibly compromising cognitive processes later in life. We examined whether exposure to chronic unpredictable stress in adolescence affects spatial ability in late adulthood. We evaluated spatial learning, reference and working memory, as well as long-term retention of visuospatial cues using a radial arm water maze. We found that stress in adolescence decreased the rate of improvement in spatial learning in adulthood. However, we found no overall performance impairments in adult reference memory, working memory, or retention caused by adolescent-stress. Together, these findings suggest that adolescent-stress may alter the strategy used to solve spatial challenges, resulting in performance that is more consistent but is not refined by incorporating available spatial information. Interestingly, we also found that adolescent-stressed rats showed a shorter latency to begin the water maze task when re-exposed to the maze after an overnight delay compared with control rats. This suggests that adolescent exposure to reoccurring stressors may prepare animals for subsequent reoccurring challenges. Overall, our results show that stress in adolescence does not affect all cognitive processes, but may affect cognition in a context-dependent manner.

Highlights

• -Rats were reared with or without chronic unpredictable stress in adolescence.
• -In adulthood, spatial cognitive abilities were tested in a radial arm water maze.
• -Prior-stressed rats began searching faster in the maze after an overnight delay.
• -Prior stress may facilitate faster action in challenging situations.
• -Prior stress did not affect learning, reference or working memory, or retention.

     

Use of an Eight-arm Radial Water Maze to Assess Working and Reference Memory Following Neonatal Brain Injury

Working and reference memory are commonly assessed using the land based radial arm maze. However, this paradigm requires pretraining, food deprivation, and may introduce scent cue confounds. The eight-arm radial water maze is designed to evaluate reference and working memory performance simultaneously by requiring subjects to use extra-maze cues to locate escape platforms and remedies the limitations observed in land based radial arm maze designs. Specifically, subjects are required to avoid the arms previously used for escape during each testing day (working memory) as well as avoid the fixed arms, which never contain escape platforms (reference memory). Re-entries into arms that have already been used for escape during a testing session (and thus the escape platform has been removed) and re-entries into reference memory arms are indicative of working memory deficits. Alternatively, first entries into reference memory arms are indicative of reference memory deficits. We used this maze to compare performance of rats with neonatal brain injury and sham controls following induction of hypoxia-ischemia and show significant deficits in both working and reference memory after eleven days of testing. This protocol could be easily modified to examine many other models of learning impairment.     

Transgenic expression of androgen receptors improves spatial memory retention in both sham-irradiated and 137Cs gamma-irradiated female mice

Using a water maze, it has been shown that both wild-type and apoE4-expressing female mice are at greater risk of developing age-related hippocampal-dependent impairments in spatial learning and memory than age-matched male mice of the same genotype. In addition, apoE4-expressing female mice were more sensitive to 137Cs gamma-radiation-induced impairment in spatial learning and memory than age-matched male mice of the same genotype. These findings imply that androgen receptors (ARs) contribute to spatial learning and memory, posing the question as to whether transgenic expression of AR in female mice might modulate hippocampal-dependent learning and memory under baseline conditions and after local brain irradiation. Hippocampal-dependent novel location recognition was comparable in wild-type and AR-Tg female mice. This function was impaired after irradiation in AR-Tg but not wild-type mice. In contrast, sham-irradiated wild-type and AR-Tg female mice showed hippocampal-independent novel location recognition, and this was not affected by radiation. After the second day of hidden platform training, in a water maze probe trial, sham-irradiated and irradiated AR-Tg female mice showed spatial memory retention but irradiated wild-type mice did not. After the third day of hidden platform training, only irradiated wild-type female mice did not show spatial memory retention in the water maze probe trial. Both sham-irradiated and irradiated wild-type and AR-Tg female mice showed passive avoidance learning and memory. These data support an important role for AR in spatial memory retention in water maze probe trials in female mice under baseline conditions and after cranial irradiation.     

fMRI Hippocampal Activity During a VirtualRadial Arm Maze

Numerous studies have shown that the hippocampus is critical for spatial memory. Within nonhuman research, a task often used to assess spatial memory is the radial arm maze. Because of the spatial nature of this task, this maze is often used to assess the function of the hippocampus. Our goal was to extrapolate this task to humans and examine whether healthy undergraduates utilize their hippocampus while performing a virtual reality version of the radial arm maze task. Thirteen undergraduates performed a virtual radial arm maze during functional magnetic resonance imaging. The brain maps of activity reveal bilateral hippocampal BOLD signal changes during the performance of this task. However, paradoxically, this BOLD signal change decreases during the spatial memory component of the task. Additionally, we note frontal cortex activity reflective of working memory circuits. These data reveal that, as predicted by the rodent literature, the hippocampus is involved in performing the virtual radial arm maze in humans. Hence, this virtual reality version may be used to assess the integrity of hippocampus so as to predict risk or severity in a variety of psychiatric disorders.     

Spatial Learning Potentiates the Stimulation of Phosphoinositide Hydrolysis by Excitatory Amino Acids in Rat Hippocampal Slices

Stimulation of phosphoinositide (PI) hydrolysis by excitatory amino acids (glutamate and ibotenate) or norepinephrine was potentiated in hippocampal slices from rats trained in an eight-arm radial maze, used as a test of spatial learning. No difference in basal or carbamylcholine-stimulated PI hydrolysis was found between control and trained animals. An increased PI response to excitatory amino acids and norepinephrine was not found in hippocampal slices prepared from animals trained in a shock conditioning avoidance test. These results suggest a possible involvement of specific glutamate receptors coupled with PI hydrolysis in the synaptic mechanisms underlying formation and/or storage of spatial memory.     

Protective effects of methanol extract of Acori graminei rhizoma and Uncariae Ramulus et Uncus on ischemia-induced neuronal death and cognitive impairments in the rat

Acori graminei rhizoma (AGR) and Uncariae Ramulus et Uncus (URE) have been widely used as herbal medicine against ischemia. In order to investigate whether AGR and URE influenced cerebral ischemia-induced neuronal and cognitive impairments, we examined the effect of AGR and URE on ischemia-induced cell death in the striatum, cortex and hippocampus, and on the impaired learning and memory in the Morris water maze and radial eight-arm maze in rats. After middle cerebral artery occlusion (MCAO) for 2 h, rats were administered saline, AGR or URE (100 mg/kg, p.o.) daily for three weeks, followed by their training to the tasks. In the water maze test, the animals were trained to find a platform in a fixed position during 6 days and then received a 60-s probe trial in which the platform was removed from the pool on the 7th day. In the radial eight-arm maze, animals were tested six times per week for 1 week. Rats with ischemic insults showed impaired learning and memory on the tasks. Pretreatment with AGR and URE produced a significant improvement in escape latency to find the platform in the Morris water maze and in the number of choice errors in the radial arm maze test. Consistent with behavioral data, pretreatments with AGR and URE significantly reduced ischemia-induced cell death in the hippocampal CA1 area. These results demonstrated that AGR and URE have a protective effect against ischemia-induced neuronal loss and learning and memory damage. Our studies suggest that AGR and URE may be useful in the treatment of vascular dementia.     

The effect of alcoholization on the behavioral reactions of rats in an 8-arm radial maze

The influence of 20% alcohol consumption on training of low-active rats in 8-arm radial maze was studied. One group of animals was trained before and the other group after the alcoholization. All the animals acquired the conditioned reaction in the radial maze. However, the behavioral difference between the groups consisted in spatially-motor asymmetry. The rats trained before the alcohol consumption had less stereotyped behavior and more distinctly preferred to enter the maze arms at the angle of 45 degrees than the animals trained after the alcohol consumption. After the alcohol consumption, rats more frequently refused from behavioral task performance in comparison with the animals trained after the alcoholization. The influence of alcohol consumption of learning and memory in low-active rats is discussed.     

Small-scale spatial cognition in pigeons

Roberts and Van Veldhuizen's [Roberts, W.A., Van Veldhuizen, N., 1985. Spatial memory in pigeons on the radial maze. J. Exp. Psychol.: Anim. Behav. Proc. 11, 241-260] study on pigeons in the radial maze sparked research on landmark use by pigeons in lab-based tasks as well as variants of the radial-maze task. Pigeons perform well on open-field versions of the radial maze, with feeders scattered on the laboratory floor. Pigeons can also be trained to search precisely for buried food. The search can be based on multiple landmarks, but is sometimes controlled by just one or two landmarks, with the preferred landmarks varying across individuals. Findings are similar in landmark-based searching on a computer monitor and on a lab floor, despite many differences between the two kinds of tasks. A number of general learning principles are found in landmark-based searching, such as cue competition, generalization and peak shift, and selective attention. Pigeons also learn the geometry of the environment in which they are searching. Neurophysiological studies have implicated the hippocampal formation (HF) in avian spatial cognition, with the right hippocampus hypothesized to play a more important role in the spatial recognition of goal locations. Most recently, single-cell recording from the pigeon's hippocampal formation has revealed cells with different properties from the classic 'place' cells of rats, as well as differences in the two sides of the hippocampus.     

Effect of losartan and enalapril on cognitive deficit caused by Goldblatt induced hypertension

The present study was designed to evaluate the learning and memory, in an altered physiological state associated with increased blood pressure and activated renin angiotensin system in Wistar rats. The role of angiotensin in cognitive function was assessed by treatment with angiotensin converting enzyme (ACE) inhibitor enalapril (2 mg/kg), angiotensin 1 receptor (AT(1)) antagonist losartan (5 mg/kg) and their combination. The experimental renal hypertension was induced by the method of Goldblatt. Learning and memory was assessed using the radial arm maze test. Acetylcholine esterase (AChE) levels in the pons medulla, hippocampus, striatum and frontal cortex were measured as a cholinergic marker of learning and memory. Results indicate that in comparison to normotensive rats, renal hypertensive rats committed significantly higher number of errors and took more trials and days to learn the radial arm maze learning and exhibited memory deficit in the radial arm maze retrieval after two weeks of retention interval, indicating impaired acquisition and memory. Treatment with enalapril, losartan and their combination attenuated the observed memory deficits indicating a possible role of renin angiotensin system in cognitive function. AChE level was reduced in hippocampus and frontal cortex of renal hypertensive rats which could be attributed to the observed memory deficit in hypertensive rats. It can be concluded that, renal hypertensive rats had a poor acquisition, retrieval of the learned behavior, perhaps a possible disturbance in memory consolidation process and that this state was reversed with ACE inhibitor enalapril and AT 1 receptor antagonist losartan.     

Animal memory: episodic-like memory in rats

Recent experiments with rats on a radial maze indicate that they can remember what foods they encountered, and when and where they encountered them. These findings, and others with food-storing birds, challenge the idea that only humans have episodic memory.     

Involvement of reduced acetylcholine release in Delta9-tetrahydrocannabinol-induced impairment of spatial memory in the 8-arm radial maze

To clarify the mechanism by which Delta9-tetrahydrocannabinol, a major psychoactive component of marijuana, impairs spatial memory in the 8-arm radial maze in rats via the cholinergic system, we used two acetylcholinesterase inhibitors, physostigmine and tetrahydroaminoacridine. Moreover, we examined the effect of Delta9-tetrahydrocannabinol on acetylcholine release in the frontal cortex and dorsal and ventral hippocampus using in vivo microdialysis. Physostigmine (0.01-0.05 mg/kg, i.p.) and tetrahydroaminoacridine (1-5 mg/kg, p.o.) improved the impairment of spatial memory induced by Delta9-tetrahydrocannabinol (6 mg/kg, i.p.) in the 8-arm radial maze. Delta9-tetrahydrocannabinol (6 mg/kg, i.p.) produced a significant decrease in acetylcholine release in the dorsal hippocampus as assessed by microdialysis. Moreover, tetrahydroaminoacridine at a dose of 1 mg/kg, which improved the impairment of spatial memory, reversed the decrease in acetylcholine release induced by Delta9-tetrahydrocannabinol in the dorsal hippocampus during 60-120 min after the Delta9-tetrahydrocannabinol injection. These findings suggest that inhibition of the cholinergic pathway by reduced acetylcholine release is one of the means by which Delta9-tetrahydrocannabinol impairs spatial memory in the 8-arm radial maze.