Effects of social facilitation for locating feeding sites by cattle in an eight-arm radial maze

A study was conducted in an eight-arm radial maze to determine if cattle with various foraging experiences could facilitate location of feeding sites by other cattle. Heifers assigned as "followers" (n=24) were initially trained to expect straw at the end of each arm. Initial training of heifers assigned as "leaders" (n=12) differed based on the three following treatments:(1) no-experience, (2) barley in the same two arms, and (3) barley in two arms but locations changed daily. During training, leaders with barley in fixed locations foraged more efficiently by traveling to fewer (P<0.05) arm ends to find barley than leaders in the variable treatment. After training, two followers were placed in the maze with a leader, and barley was available in two arms. Leaders facilitated the location of barley by followers. In 61% of the occasions that followers first found barley, leaders were at the feeding site. Eighty-one percent of followers later located barley without leaders in the maze. Followers with experienced leaders did not find barley consistently more often than heifers with inexperienced leaders. Cattle can apparently learn feeding site locations from other animals, but additional research is needed to evaluate the behavioral mechanisms that influence social facilitation during foraging.     

Behavioral tactics among rats in a radial maze

The experiments were carried out on rats of Wistar (W) and Krushinsky-Molodkina (KM) lines, differing in the level of task performance in conditions of multiple choice of food sources in a 12ray radial symmetrical maze. It is shown that in the radial maze, the rats of both lines use a number of behavioural tactics. To determine the influence of changes of environmental spatial characteristics while preserving the main experimental strategy--never revisit the places of reinforcement,--on the peculiarities of tactics manifestations maze modifications were elaborated. Besides the environmental procedure was changed. Under all conditions the rats of W line solved the task. According to the situation, they either preserved former tactics or developed some new ones. The rats of KM line could not solve the task in changed conditions. In most sessions, appearance or absence of given tactics was not adequate to new conditions. The presence of the necessary tactics not always facilitated the task solving. Thus, for the realization of adequate reactions, the presence of necessary tactics is not sufficient: their "tuning" is needed depending on situation. The possibility is supposed of genetic determination of rats ability to some tactics. However, it is emphasized, that tactics are not strongly fixed, as their realization depends on environmental conditions.     

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.     

Capacity of working memory in rats as determined by performance on a radial maze

Capacity of the working memory was tested in 12 rats highly overtrained in the 12- and 24-arm radial mazes. Asymptotic performance levels were characterized by 1.01 and 2.78 errors/trial in the 12- and 24-arm mazes, respectively. The incidence of errors increased from 31% on the last choice in the 12-arm maze to 51% on choices 23 and 24 in the 24-arm maze, but remained significantly below the expected error probability of about 85%. Linear extrapolation of the above trend to mazes with more arms suggests working memory capacity of 40 to 50 items. When two trials in a 12-arm maze were repeated in immediate succession, error incidence increased from 1.17 in the first trial to 2.13 in the second trial. The tendency to avoid choice repetition could be observed in any string of 12 continuous choices, but was weakest in segments divided by trial boundary (2.48 errors in choices 7 to 18). With a different trial separation (choices 1–6 and 19–24 in maze A, choices 7–18 in an adjacent maze B) errors dropped to 1.09 in B but increased to 2.30 in A. It is concluded that radial maze performance reflects avoidance of choice repetition which is improved by recognition of trial boundaries and is adversely influenced by forgetting and interference.     

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.     

Behavioral tactics of rats receiving unequally distributed reinforcement in a radial maze

Rats behaviour was studied in 12-arms radial maze with food reinforcement of different volumes presented only in 6 passages. Dynamics of changes is shown in the process of learning both in the preference of the passages with greater volume of reinforcement and in the number of errors, characterizing the working and referent memories. In the trained rats, their behaviour is determined by at least two behavioural tactics: visiting more remote passages and choice in the beginning of the test of more reinforced passages.     

Training of rats of the Wistar and Krushinskii-Molodkinaia lines in a radial maze

The experiments were conducted on rats of Wistar (W) and Krushinsky--Molodkina (KM) (with audiogenic epilepsy) lines in 12-rays radial-symmetrical labyrinth. The trained rats of W line made less erroneous (repeated) visits to the labyrinth corridors than the rats of KM line. The corridors repeatedly visited by the rats of W line were more frequently situated near the unvisited corridors. No definite sequence of corridors' visiting by the rats of both lines was observed; still there was a tendency to choose corridors the most remoted from each other. This tendency intensified in the process of training. This is considered as one of tactics of rats' behaviour, providing for adequate reactions in definite surrounding conditions.     

Neonatal exposure to intermittent hypoxia enhances mice performance in water maze and 8-arm radial maze tasks

Hypoxia has generally been reported to impair learning and memory. Here we established a hypoxia-enhanced model. Intermittent hypoxia (IH) was simulated at 2 km (16.0% O2) or 5 km (10.8% O2) in a hypobaric chamber for 4 h/day from birth to 1, 2, 3, or 4 week(s), respectively. Spatial learning and memory ability was tested in the Morris water maze (MWM) task at ages of postnatal day 36 (P36)-P40 and P85-89, respectively, and in the 8-arm maze task at P60-68. The long-term potentiation (LTP), synaptic density, and phosphorylated cAMP-responsive element-binding protein (p-CREB) level in the hippocampus were measured in mice at P36 under the IH for 4 weeks (IH-4w). The results showed that IH for 3 weeks (IH-3w) and IH-4w at 2 km significantly reduced the escape latencies of mice at P36-40 in the MWM task with significantly enhanced retention, and this spatial enhancement was further confirmed by the 8-arm maze test in mice at P60-68. The improvement in MWM induced by IH-4w at 2 km was still maintained in mice at P85-89. IH-4w at 2 or 5 km significantly increased amplitude of LTP, the number of synapse, and the p-CREB level in the hippocampus of P36 mice. These results indicated that IH (4 h/day) exposure to neonatal mice at 2 km for 3 or 4 weeks enhanced mice spatial learning and memory, which was related to the increased p-CREB, LTP, and synapses of hippocampus in this model.     

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.     

Contextual control of rats' foraging behaviour in a radial maze

This study demonstrated that with experience rats were able to discriminate the background contextual cues in order to foraging correctly in an eight-arm radial maze if the background contexts signaled to the rats which of two bait patterns was in effect in that context. Four of the eight arms were context-dependent: two arms were baited in the "night" context, while the other two were baited in the "daytime" context. The remaining four arms were context-independent: three of them were never baited, while the remaining one was baited in both contexts. The rats gradually began to avoid the arms that were uniquely baited in the other context, suggesting a contextual or conditional control of arm selection. Interestingly, these rats also showed better performance in avoiding the never-baited arms, compared with control rats. Namely, disambiguating the incentive values of the four arms by contextual cues collaterally facilitated the context-independent arm performance. Another interesting finding of the present study is that the rats did not visit the always-baited arm earlier than the arms uniquely baited in that context.     

Tetrachlorodibenzo-p-dioxin exposure alters radial arm maze performance and hippocampal morphology in female AhR mice

Perinatal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been reported to alter spatial learning in rats tested on a radial arm maze (RAM). TCDD is believed to exert most of its effects through binding to the aryl hydrocarbon receptor (AhR). To determine whether the AhR mediates TCDD-induced alterations in spatial learning, we tested male and female AhR-knockout (AhR-/-), heterozygous (AhR+/-) and wild-type (AhR+/+) mice on the RAM. AhR+/- male and female mice were time mated, and treated dams were dosed with 5 microg TCDD/kg body weight on day 13 of gestation. When offspring reached adulthood, male and female AhR+/+, AhR+/- and AhR-/- mice from TCDD-exposed and unexposed litters were tested on the eight-arm RAM. After testing, we examined hippocampal morphology as visualized by the Timm's silver sulfide stain. TCDD-exposed female AhR+/- mice made more errors than their respective controls on the RAM and exhibited a decrease in the size of the intra- and infrapyramidal mossy fiber (IIP-MF) field of the hippocampus. None of the other TCDD-exposed groups differed from their respective control groups with regard to maze performance or hippocampal morphology. The reduction of IIP-MF field indicates a possible morphological basis for the learning deficit that was observed in the female AhR+/- mice. It is hypothesized that the effect of TCDD exposure is AhR dependent and that TCDD may alter GABAergic activity in the hippocampus of female mice during development.     

Participation of the nucleus accumbens in acquisition of spatial choice behavior in rats performing in a radial plus maze

The role of medial shell of the nucleus accumbens in acquisition of spatial behavior was studied in rats performing choice task in radial maze with asymmetrical water reinforcement. It has been found that the nucleus accumbens lesioned rats failed in finding larger rewards but preserve their reward-seeking behavior guided by visual discriminative stimuli. The results obtained are in good agreement with suggestion that the nucleus accumbens is a site of convergence of spatial information (from hippocampus) with reward information (from amygdala and VTA), providing bridge for effective limbic-motor interface underlying motivated goal-directed behavior in animals.     

Analysis of kinetics of consecutive metabolic cerebral activations induced by spatial discrimination testing, using (14C)-glucose, in an eight-arm radial maze in mice

Regional mapping of relative (14C)-glucose (GLU) uptake was analyzed in Balb/c mice at 3 time intervals (5 min., 1 hr., 3 hrs.) after either the first (Day 1) or the last (Day 9) daily sessions of a spatial discrimination testing procedure in an eight-arm radial maze. On Day 1, increased labelling was found 5 min. post-training in subcortical, hippocampal and cortical regions. Decreased GLU uptake was observed 1 hr. later in the same regions, followed at 3 hrs. post-training by a retarded activation in the above areas and particularly in thalamic and cortical structures. On Day 9, there was only an early (5 min.) post-training increase in metabolic activity followed by a subsequent monotonic decrease over 3 hrs. post-training period.     

The olfactory orientation traits of white rats in a maze]

Some characteristics of olfactory behaviour of albino rats in three-arm maze have been studied. It was found that the olfactory discrimination of different food reinforcements may be elaborated in passages as long as 90 cm. Choice reactions were determined by olfactory, not visual, stimuli on their simultaneous presentation.     

Effects of amyloid beta peptide (25-35) on the behavior of rats in a radial maze

Impairment of cognitive functions, particularly long-term (episodic) and working memory, is one of the earliest prognostic symptoms of Alzheimer's disease, both cognitive impairment and neurodegeneration being mediated by amyloid-beta neurotoxicity. Effects of intracerebroventricular administration of amyloid-beta peptide (25-35) [A beta(25-35)] to rats on the retention of previously learned task in an 8-armed radial maze was studied. A beta(25-35) was injected bilaterally, at doses of 15 or 30 nmol/rat, 7 days after the preliminary learning. The performance in the maze was tested 60 days after the surgery. A beta(25-35) impaired the short-term memory, with no significant effect on the long-term memory. No dose dependence could be demonstrated.     

The cholinesterase inhibitor, phenserine, improves Morris water maze performance of scopolamine-treated rats

Male Fischer-344 rats (n = 38) at 5 months old were tested in a Morris water maze to determine if treatment with the cholinesterase inhibitor, phenserine (PHEN), would overcome a learning impairment induced by scopolamine (SCOP), a muscarinic cholinergic receptor antagonist. Each rat was randomly assigned to one of five groups to receive two intraperitoneal injections 60 and 30 min, prior to testing, respectively, as follows: (1) saline-saline (SAL); (2) saline-1.0 mg/kg (SCOP); (3) 2 mg/kg PHEN- SCOP (PHEN2); (4) 4 mg/kg PHEN-SCOP (PHEN4); and (5) 1 mg/kg PHEN-SAL (PHEN1). Maze testing occurred across 5 days with 4 days of acquisition trials (4 trials per day) and a fifth day consisting of a single 120 sec probe trial. PHEN1 and SAL were combined into one control (CON) group for purposes of statistical analysis for both acquisition and probe trials as comparison of the two groups revealed that they did not significantly differ on any measure. SCOP-treated rats were significantly impaired compared to CON in learning the location of the submerged platform as measured by latency to locate the platform and the distance traversed to find the platform across days of testing. The PHEN4 group had significantly lower latencies and traveled a shorter distance to reach the submerged platform when compared to SCOP on the fourth day of trials while the PHEN2 group traveled more directly to the submerged platform but did not have shorter latencies than the SCOP group. For probe trials, CON rats swam closer to the target area (a measure of proximity to the removed platform) than did all other groups, and the PHEN4 group swam in an area more proximate to the target area than did the SCOP-treated group. These findings demonstrate the ability of this drug to improve learning when cholinergic function has been impaired in a spatial memory task.