[The effect of a caudal hippocampus lesion on learning in a Morris water maze in bank voles (Clethrionomys glareolus)].

A bilateral cytotoxic lesion of the caudal hippocampus (about 1/3 of the whole hippocampus, which is insufficiently studied) influences learning of bank voles (Clethrionomys glareolus) in the Morris water maze. This effect has been estimated in this paper. A version of the test intended to measure long-term spatial memory was used. The lesion was shown to exert an influence on the learning dynamics by slowing it down, as well as to reduce the accuracy of platform location memorizing at early stages of training. The data obtained indicate the involvement of this area in control of spatial learning in rodents.

[C57BL/6 mice open field behaviour qualitatively depends on arena size].

Open field behavior is well known to depend on physical characteristics of the apparatus. However many of such effects are poorly described especially with using of modern methods of behavioral registration and analysis. The previous results of experiments on the effect of arena size on behavior are not numerous and contradictory. We compared the behavioral scores of four groups of C57BL/6 mice in round open field arenas of four different sizes (diameter 35, 75, 150 and 220 cm). The behavior was registered and analyzed using Noldus EthoVision, WinTrack and SegmentAnalyzer software. A significant effect of arena size was found. Traveled distance and velocity increased, but not in proportion to increase of arena size. Moreover a significant effect on segment characteristics of the trajectory was revealed. Detailed behavior analysis revealed drastic differences in trajectory structure and number of rears between smaller (35 and 75 cm) and bigger (150 and 220 cm) arenas. We conclude, that the character of exploration in smaller and bigger arenas depends on relative size of central open zone in arena. Apparently its extension increases the motivational heterogeneity of space, that requires another than in smaller arenas, strategy of exploration.

[Inhomogeneous hippocampal activation along the rostrocaudal axis in mice after exploration of novel environment].

Levels of the c-Fos protein expression in neurons were used as an index of neural activation in the hippocampus of C57BL/6 mice after their exploration of novel environments. C-Fos expression was measured at 8 levels along the rostrocaudal axis of the hippocampus. In Experiment 1, C57BL/6 mice were trained in a modified 8-arm radial maze to find the entry to a home cage through a target arm (1 day, 6 trials). Animals of control group were trained to enter the home cage through an isolated arm. In mice trained in 8-arm maze, functional rostrocaudal inhomogeneity of hippocampus was found. C-Fos expression was increased, mainly, in the caudal parts of CA1, CA3 and dentate gyrus as compared to the control group. In Experiment 2, C57BL/6 mice were tested (1 day, 6 trials) in a novel open-field arena. In this case, c-Fos activity was increased in CA1 (to a greater extent in the caudal than in rostral parts) and CA3 and dentate gyrus (equally in rostrocaudal direction). Significant positive correlations between the exploration activity and density of c-Fos positive cells were found in both experiments. The findings suggest that exploration in novel environment differentially affects the hippocampal subfields along the hippocampal rostrocaudal axis.

[Solving of Revesh-Krushinsky test by animals of different taxonomic groups].

There has been compared behavior of rats, corvid birds, and primates of different species at their performance of the Revesh-Krushinsky test (RKT) developed by L. V. Krushinsky to extimate the human capability for revealing rule of discrete translocation of hidden target object. RKT was introduced as an addition to the test for extrapolation of the movement direction of the bait seen only at the initial pathway fragment; this test is close to Piaget's tests (stage 6) evaluating the capability for mental representation and determination of location of the moving hidden object. During RKT, the bait, hidden from the animals, was placed, near where it was previous time: at the first test presentation--under the 1st cylinder, at the 2nd one--under the 2nd cylinder, etc. The animals were tested once. It was shown that they did not catch the necessary for successful solution rule of the bait translocation, direction and step of its translocation in each presentation. Only some of the animals solved RKT, found the bait 3 and more times in succession with no errors or with one error. Nevertheless, in all groups the number of errors was lower than that in the model situation of random search. Such optimization was a consequence of universal for all groups strategy of search in the places where the bait was found recently. With the similar number of errors, rats, birds, and monkeys performed the search differently. Rats were looking for bait mainly among the cylinders where they had found it previously, whereas monkeys and birds chosen the first the new cylinders located near the target one, which implies the existence, to the weak extent, of elements of prognosis. For all groups of animals, RKT turned out to be more difficult both of the test for extrapolation and the Piaget's test.

Behavior and spatial learning in radial mazes in birds.

This review addresses studies of spatial memory and learning in birds performed using the radial maze method. Descriptions of different versions of this test (standard and "giant" tunnel-type mazes, as well as unstructured "analogs") are described and the methodological problems of testing birds are discussed. Behavioral measures from birds and laboratory rats, as the "standard" system for radial maze studies, are compared. The characteristics of spatial learning in birds of different systematic groups (pigeons, tits, corvids, chickens, etc.) are compared. Particular attention is paid to studies addressing spatial memory in closely related bird species with different ecological features, in terms of the ability to hoard food and finding their hoards after prolonged time periods, as well as to the few reports of results from experiments with migrant birds and homing pigeons.

[Behavior and spatial learning in birds in radial maze].

Studies of spatial learning and memory of birds in radial maze are reviewed. The radial maze variants (standard, giant and open-field analog) are described; procedural problems of bird testing are discussed. Radial maze task performance of birds is compared with that of laboratory rats as a well-studied standard. Specific features of spatial learning in various taxonomic avian groups (pigeon, tits, corvids, chickens and others) are considered. The results of spatial memory studies in closely-related species with different ecology (food storing behavior, degree of caching specialization) and experiments with migrant birds and homing pigeons are discussed.

[Spatial memory in bank voles (Clethrionomys glareolus Schreb) assessed in the cue-controlled open field with the place of refuge].

The capacity of bank voles (Clethrionomys glareolus Schreb) for rapid spatial learning was assessed in cue-controlled open field using their species-specific habits (high fear). Animals were tested in open field after 3 days of pretraining. During testing, novel stimuli (black-and-white geometric figures arranged in symmetric or asymmetric modes for different vole groups) were attached to a curtain surrounding the open field, and a shelter (a familiar box from the home cage) was introduced into the field. Testing consisted of four 10-min trials, the last (probe) trial was performed without the shelter. Time spent in different fielld areas was recorded. The voles remembered previous location of the shelter and preferred to visit this area. It was possible only in the condition with asymmetric arrangement of visual stimuli when animals could use them for navigation. The findings conclude that bank vole have a good capacity for rapid spatial learning.

Features of the expression of the c-Fos gene along the rostrocaudal axis of the hippocampus in common voles after rapid training to solve a spatial task.

The level of expression of the c-Fos protein in neurons was used as a measure of the activation of transcription in the hippocampus of common voles (Microtus arvalis Pall.) after rapid spatial training. Stained Fos-positive cells were counted on 20 brain sections along the rostrocaudal axis of the hippocampus. Voles were trained to find the exit to their home cages through one of the arms of a modified eight-arm radial maze (using a 2-h series of six trials on one day). Animals were initially trained to leave the home cage via an arm not connected to the maze. Voles of the "active" control group were passed through the isolated arm into the home cage six times on the experimental day. Animals for the "passive" control for c-Fos levels were collected from their home cages. Significant increases in c-Fos expression in voles trained in the maze and the active control group, as compared with passive controls, were seen in all areas studied (hippocampal fields CA1 and CA3 and the dentate fascia). At the same time, a significant increase in the number of c-Fos-positive neurons in voles trained in the maze, as compared with the active controls, was noted only in the caudal hippocampus, no differences being seen in the rostral part. The greatest levels of activation were seen in the dentate fascia and field CA3. These results provide evidence for the heterogeneous functioning of the hippocampus along the rostrocaudal axis during training of voles to solve a spatial task.

[Features of the c-Fos gene expression along the hippocampal rostro-caudal axis in common voles after rapid spatial learning].

The levels of the Fos protein expression in neurons was used as an index of transcription activation in the hippocampus of common voles (Microtus arvalis Pall.) after their rapid spatial learning. Fos-positive cells were stained and calculated in 20 brain sections along hippocampal rostro-caudal axis. Voles (learning group) were trained in a modified 8-arm radial maze to find the entry to the home cage through a target arm (6 trials per session, 2-hour session). The animals were pretrained to enter the home cage through an arm isolated from the maze. Animals of active control group continued entering the home cage through the isolated arm, and animals of the passive control group were taken for the Fos immunohistochemistry from the home cage. Both in the learning group and active control group, a significant increase in c-Fos expression was shown in all the examined areas (CA1, CA3 and the dentate gyrus) as compared to the passive control. A significant increase in the number of c-Fos positive neurons was observed in the caudal hippocampus of the learning animals as compared to the active control, however, no differences were found in the rostral part. The maximum effects were observed in the dentate gyrus and the CA3 field. The results suggest a functional rostro-caudal inhomogeneity of the vole's hippocampus in the spatial learning task.

Role of a neuronal small non-messenger RNA: behavioural alterations in BC1 RNA-deleted mice.

BC1 RNA is a small non-messenger RNA common in dendritic microdomains of neurons in rodents. In order to investigate its possible role in learning and behaviour, we compared controls and knockout mice from three independent founder lines established from separate embryonic stem cells. Mutant mice were healthy with normal brain morphology and appeared to have no neurological deficits. A series of tests for exploration and spatial memory was carried out in three different laboratories. The tests were chosen as to ensure that different aspects of spatial memory and exploration could be separated and that possible effects of confounding variables could be minimised. Exploration was studied in a barrier test, in an open-field test, and in an elevated plus-maze test. Spatial memory was investigated in a Barnes maze and in a Morris water maze (memory for a single location), in a multiple T-maze and in a complex alley maze (route learning), and in a radial maze (working memory). In addition to these laboratory tasks, exploratory behaviour and spatial memory were assessed under semi-naturalistic conditions in a large outdoor pen. The combined results indicate that BC1 RNA-deficient animals show behavioural changes best interpreted in terms of reduced exploration and increased anxiety. In contrast, spatial memory was not affected. In the outdoor pen, the survival rates of BC1-depleted mice were lower than in controls. Thus, we conclude that the neuron-specific non-messenger BC1 RNA contributes to the aptive modulation of behaviour.

[Conditioning of gray crows (Corvus cornix L.) in a "giant" eight-arm radial maze]. / Obuchenie serykh voron (Corvus cornix L.) v "gigantskom" 8-rukavnom radial'nom labirinte.

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.

[Behavioral impairments in Morris water maze in rats selectively bred for audiogenic seizure susceptibility (Krushinsky-Molodkina strain)]. / Povedenie v vodnom teste Morrisa krys linii Krushinskogo-Molodkinoi, selektirovannykh na povyshennyiu sudorozhnuiu gotovnost'.

Krushinsky-Molodkina rats (KM strain) with genetically determined seizure susceptibility (clonic and tonic seizures in response to the sound of an electric bell, Krushinsky, 1960) were tested in two versions of Morris water maze and compared with normal albino rats (Sprague-Dawley and Wistar). The tests revealed a learning deficit in KM rats. They showed slow acquisition in both the spatial version of the test and the version with the platform, less efficient strategy of searching for target platform, and high scores of floating and thigmotaxis. However, males of KM rats (not females) did not differ significantly from Wistar strain in the probe trial in the spatial variant of the Morris test. No preference for searching for the platform at the place of its previous localization was observed in KM females. Together with our previous findings of the low scores in Revecz-Krushinsky test and data of other authors (Batuev et al., 1983) concerning a working memory deficit in the radial maze, the results suggest the of complex cognitive deficit combined with possible increased stress reactivity in KM rats.

[Structural abnormalities of hippocampus in 101/HY mice]. / Anomalii stroeniia gippokampa y myshei linii 101/HY.

We studied cytoarchitectonics of the hippocampus in 101/HY and CBA mice on brain sections stained after Nissl and Timm. In CBA mice, the structure of hippocampus was normal. In 10/HY mice, stratum pyramidale in field CA3 was "splitted" and the density of pyramidal neurons was decreased. Abnormalities were also found in the zone of suprapyramidal projections of mossy fibers (sp-ME), i.e., terminals of axons of the fascia dentata granular cells on the apical dendrites of pyramids. If in CBA mice the sp-MF zone was normal, i.e., looked like a vast compact formation or dense ordered bundle, in 101/HY mice, the sp-MF zone represented a group of scattered, diffuse, and interrupted bundles of varying length, some of which were incorporated in stratum pyramidale. Possible causes of the described morphological abnormalities are discussed, as well as their relation to specific features of biology, behavior, and neurological status of 101/HY mice.

A large outdoor radial maze for comparative studies in birds and mammals.

For a comparative neurobiological analysis of spatial learning and memory, a large outdoor eight-arm radial maze was constructed which permits behavioral assessment of many avian and mammalian species both from the laboratory or the wild, using the same metric space and session schedules. It consists of a central part of 250cm diameter, and has arms of 650cm length, 170cm height and 80cm width. In order to determine appropriate training schedules for comparison of different species, we tested four mammalian and two avian species during 9-15 sessions: 18 albino rats (Rattus norvegicus), nine outdoors and nine in a conventional small indoor maze; six guinea pigs (Cavia porcellus); six rabbits (Oryctolagus cuniculus); five hedgehogs (Erinaceus europaeus); seven hooded crows (Corvus corone cornix) and six chickens (Gallus domesticus). Rats learned fast in both mazes yet significantly better in the large one. Good-to-excellent learning was also observed in juvenile rabbits and wild-caught crows, although the latter tended to avoid arms in the vicinity of the observer. Hedgehogs and chickens did not show significant learning as a group, but some individuals appeared to learn the task. Guinea pigs remained continuously passive and could not be trained. Thus, in spite of species-specific demands for reward, adaptation and pre-training, this type of radial maze permits to directly compare a wide variety of species. Such comparability is essential for an analysis of underlying neurobiological mechanisms.

Hippocampal mossy fibers and swimming navigation learning in two vole species occupying different habitats.

We showed previously for mice that size differences of the infrapyramidal hippocampal mossy fiber projection (IIP-MF) correlate with spatial learning abilities. In order to clarify the role of the IIP-MF in a natural environment, we studied the bank vole (Clethrionomys glareolus), adapted to a wide range of different habitats, and the root vole (Microtus oeconomus), living in homogenous grassland habitats with small home ranges. Morphometry on Timm-stained horizontal brain sections of six C. glareolus and six M. oeconomus revealed that the size of the entire mossy fiber projection was 42% larger in C. glareolus than M. oeconomus. C. glareolus had also an IIP-MF projection about 230% larger than that of the root vole. A sample of captured animals was then transferred to the laboratory (C. glareolus, n = 23; M. oeconomus, n = 15) and underwent testing for swimming navigation according to a standardized protocol used to assess water maze learning in about 2,000 normal and transgenic mice. Both species learned faster than laboratory mice. Overall escape times showed no differences, but path length was significantly reduced in C. glareolus, which also showed superior performance in a variety of scores assessing spatial search patterns. On the other hand, M. oeconomus showed faster swimming speed, and strong thigmotaxis combined with circular swimming. M. oeconomus also scored at chance levels during the probe trial, about as poorly as mutant knockout mice considered to be deficient in spatial memory. These differences probably reflect differential styles of water maze learning rather than spatial memory deficits: C. glareolus appears to be superior in inhibiting behavior interfering with proper spatial search behavior, while M. oeconomus succeeds in escaping by using rapid circular swimming. We assume that size variations of the IIP-MF correspond to a mechanism stabilizing hippocampal processing during spatial learning or complex activities. This corresponds to the ecological lifestyle of the two species and is in line with previous observations on the role of the IIP-MF.

[The solving of the Revecz-Krushinskii test by rats of different genotypes]. / Reshenie testa Revesha-Krushinskogo krysami raznykh genotipov.

Brown Norway rats bred from the original wild stock, KM (Krushinskii-Molodkina) albino rats selectively bred for audiogenic seizure susceptibility, and Wistar albino rats were subjected to Revecz-Krushinskii reasoning test. It determines whether rats can anticipate regular yet invisible shifts of food bait positions. A bait was placed under one of 12 opaque cylinders (arranged in a line) to be tipped by a rat in order to obtain food. In the first trial the cylinder 1 was baited, in the second trial the cylinder 2 was and so on up to 12th one. The correct strategy of this problem solving is a choice "one cylinder ahead" of the previous bait location. Rats appeared to be unable to realize this algorithm accurately. However, in some cases their performance was significantly different from chance. They apparently realized another strategy: to choose recently baited cylinders with shifting a zone of search. It was typical for brown and Wistar rats but not for KM which preferred to choose the cylinders baited in the previous trials, but their preference was not specified by recently baited positions. In the second experiment (learning of an accurate choice of one target cylinder with a fixed position in the line) the worst performance was found also in KM rats. The strain differences in Revecz-Krushinskii test performance are supposed to be caused by the level of spatial working memory.

[The solving of the Revecz-Krushinskii test by Norway rats]. / Reshenie testa Revesha--Krushinskogo krysami pasiukami.

Reasoning abilities of Norway rats were studied in Revecz-Krushinskii test. In this test 12 opaque plastic cylinders were placed in a row. Rats obtained the bait (sunflower seeds) after tipping the goal cylinder (from the feeder situated under it) independently of the number of one tipped before. Positions of the baits were changed in the following order: the cylinder No 1 in the first trial, No 2--in the second and so on up to the twelfth one. Rats were tested 3 times (12 trials, once a week) in a rectangular box with a starting chamber and a working part with a special device which excluded the influence of olfactory stimuli. Solution scores demonstrated that rats chose cylinders in the nonrandom manner and their behaviour scores were similar to those of crows and monkeys. Analysis of errors and strategies of behaviour of rats showed that quick improvement of feeding was at least partly determined by easy acquisition of recent food positions (i.e., the algorithm of shifting).

[Nonspecific grooming in rats during the solution of an extrapolation task]. / Nespetsificheskii grumming u krys pri reshenii ékstrapoliatsionnoi zadachi.

Grooming behavior in laboratory brown rats was analysed in the course of extrapolation task solving. Cases of task solution (correct and incorrect) were compared with those when animal "refused" to turn round the screen during search of food bait. In latter cases grooming episodes were more numerous, their latency and duration being higher than during former cases. At the same time the latest stages of experiment (when 8-13 trials a day twice a week were presented) were characterized by more frequent grooming occurrence as well as by longer latencies and duration of grooming episodes. When rats were given I trial a day with one week intervals grooming incidence as well as "refusals" occurrence decreased. The possible participation of animal grooming in arranging the defense reactions against excessive and inadequate activity is discussed.

[Features of the dynamics of the forebrain EEG of Emys orbicularis during the solving of an extrapolation problem]. / Osobennosti dinamiki EEG perednego mozga bolotnykh cherepakh pri reshenii ékstrapoliatsionnoi zadachi.

Sharp EEG changes are recorded in bioelectrical activity of the dorsal cortex and dorsal ventricular edge in marsh tortoises in conditions of free movement during solving of an extrapolation task (a test of elementary reasoning ability). These changes of a pathological character, accompanied by neurotic states, were observed in some animals having correctly solved the task several times in succession (2-5), beginning with the first presentation. Such changes of EEG and behaviour were not found in tortoises that committed errors at first presentations of the task and only gradually learned correct solving. Formation of the adequate behaviour can proceed by two means: on the basis of elementary reasoning ability and learning. Disturbance of adequate behaviour in the experiment with characteristic changes of EEG testifies to a difficult state of the animal during solving of the extrapolation task.