A comparative analysis of spatial orientation in a changing environment in rats with differing preliminary experience]

Comparison of rats behaviour with different preliminary experience in elaboration of the strategy of return to place of reinforcement was conducted. Significant differences in the number of selective replacements to the place of reinforcement in previous tests in experienced, inexperienced and naive rats were found. It was proved that decisive role in the appearance of the found differences played gained experience and the process of engram extraction from memory. Inhibition of search in naive rats and ability to selective use of strategies corresponding to situation in the experienced ones in condition of stress of permanent changes were shown.     

The singling out of the dominant in white rats during the acquisition of a win-stay strategy in a 3-arm maze]

Correlation of shift and stay reactions was studied in rats in the process of singling out of the win-stay dominant. It was found that in rat which had no previous experience in receiving reinforcement in multi-arm maze, both the shifts and stay reactions were observed with the dominance of the shifts. In experienced rats formation of the win-stay strategy using a new direction required learning and had three stages: the stage of initial dominant, of displacements and of singling out a new dominant. Formation of a new protracted dominant of win-stay could be gradual (through formation of short-term dominants) or uneven. At repeated changes of the reinforcement place both the tendency to uneven transfer and delayed periods in formation of the protracted dominant were observed.     

Plasticity of the behavior of Myrmica rubra ants during learning in a multi-alternative symmetric labyrinth

The ability was studied of Myrmica rubra ants to change the habit of passing through a multialternative symmetric labyrinth at motivation of the care for posterity. In exams the location of reinforcement was changed: in the first exam the progeny was carried from both aim places to those symmetric to them relatively to labyrinth cross axis; in the second exam the reinforcement was left on one aim place non-preferred during learning. The first exam was passed by 62.5% of ants, the second--by 87.5%. In the first exam such parameters were worse as the first correct decision, the mean number of movements in the cycle, the total number of correct cycles. At elaboration of new motor habits and increase and inversion were observed of the initial spatial-motor asymmetry. Individual variations in ants behaviour increased. The ants who failed to solve the task, showed pronounced signs of preneurotic state. The obtained results testify to a high plasticity of ants behaviour and their ability to modify their activity according to changes of experimental situation.     

The reinforcing property and the rewarding aftereffect of wheel running in rats: a combination of two paradigms

Wheel running reinforces the behavior that generates it and produces a preference for the context that follows it. The goal of the present study was to demonstrate both of these effects in the same animals. Twelve male Wistar rats were first exposed to a fixed-interval 30 s schedule of wheel-running reinforcement. The operant was lever-pressing and the reinforcer was the opportunity to run for 45 s. Following this phase, the method of place conditioning was used to test for a rewarding aftereffect following operant sessions. On alternating days, half the rats responded for wheel-running reinforcement while the other half remained in their home cage. Upon completion of the wheel-running reinforcement sessions, rats that ran and rats that remained in their home cages were placed into a chamber of a conditioned place preference (CPP) apparatus for 30 min. Each animal received six pairings of a distinctive context with wheel running and six pairings of a different context with their home cage. On the test day, animals were free to move between the chambers for 10 min. Results showed a conditioned place preference for the context associated with wheel running; however, time spent in the context associated with running was not related to wheel-running rate, lever-pressing rate, or post-reinforcement pause duration.     

Preference and aversion for brain stimulations estimated by the conditioned place preference

Rats implanted with chronic electrode into the medial forebrain bundle at the level of the hypothalamus (which elicited self-stimulation behaviour) display conditioned place preference after repeated stimulations of this area; conversely rats implanted into the mesencephalic dorso-medial tegmentum (which elicited switch-off behaviour) present conditioned place aversion after such repeated stimulations. Furthermore rats implanted in these two area without exhibiting self-stimulation or switch-off behaviours also display preference or aversion for the location paired with the brain stimulations. It was thus hypothesized that the conditioned place preference procedure seemed to present a higher sensitivity than the bar pressing procedures to detect preference or aversion for brain stimulation. Moreover the activation of the medial forebrain bundle which was associated with positive affect is more effective for a long term retention of the preferred location than midbrain periventricular reticular activation which induces a negative affect.     

Changes in the emotionally conditioned behavior of rats under the influence of the hexapeptide fragment GLLDLK of the protein inhibitor of diazepam binding]

It is shown that suboccipital injection of 100 micrograms of the gexapeptide GLLDLK (the fragment of endogenous peptide--the inhibitor of diazepam binding) modified (for 1-3 days) the emotionally conditioned behaviour of the rats (the test of "emotional resonance"). This modification was realized in some reinforcement of different behavioural patterns and had signs of anxiety and depression. In the test "social hierarchy" the injection of GLLDLK didn't change significantly the hierarchy in the whole rat society, but in the recipient behaviour the exploratory activity has been changed, the time of grooming increased and the quantity of social contacts decreased.     

Effect of acute and chronic deprivation of catecholaminergic system activity induced by 6-hydroxydopamine on the behavior of the rat

On 202 male rats of Wistar line, a study was carried out of the effect of chronic and acute deprivations of the brain CA-systems activity resulting from administration of 6-OHDA on investigating behaviour and learning. Chronic deprivation of CA-systems activity by neonatal administration of 6-OHDA (100 mg/kg subcutaneously) and their acute deprivation by intracerebral administration of 6-OHDA to adult rats (150 mkg in each lateral ventriculus) was accompanied by similar deep changes of behaviour. Both forms of deprivation reduced the investigating activity of the animals in the open field. In both cases, the above 6-OHDA dozes sharply impeded the learning of animals with emotionally negative reinforcement, with no significant influence on learning with emotionally positive reinforcement. Both forms of deprivation of CA-systems activity weakened the reaction of frustration elicited by a sharp reduction of food reinforcement.     

The volume of reinforcement and the structure of rat behavior in a radial labyrinth

In rats choice reaction was elaborated in 12 passages radial labyrinth with different volumes of food only in six of twelve passages. Then the conditions were modified: the first group of rats in the beginning of the experiment was placed to another labyrinth sector, and in the second group the food volume was changed in passages. In new situations in animals of both groups the reaction efficiency temporarily decreased, simultaneously the correction of behaviour structure took place. The character of behavioural tactics (tendencies to visit passages with larger food volume at the beginning of the experiment, spatial-motor asymmetry etc.) is described in dynamics of adaptation to new conditions. Factors determining the rats behaviour structure are discussed.     

Disruptive effects of lateral hypothalamic stimulation on the lick-interrupt cycle in rats

Consummatory licking at a water spout was compared with licking at a dry spout maintained by electrical hypothalamic stimulation in the same rats. Both forms of licking, recorded photoelectrically, were maintained on a fixed ratio 8 schedule. Duration of reinforcement delivery was equated [300 ms]. A computer analysis of the temporal distribution of licks in each 1024 ms period from onset of reinforcement revealed that lateral hypothalamic stimulation decreased the occurrence of licking and disrupted the normally synchronous pattern of this behaviour. An analysis of the effects of delivering lateral hypothalamic stimulation contingent on water-maintained licking revealed that this effect of stimulation was clearly current-dependent. It is proposed that differences in licking rates maintained by water and by electrical hypothalamic stimulation, respectively, are due to response interference in the latter case. This interference effect is also proposed to be a major factor underlying higher reward thresholds for self-stimulation when licking is the operant response.     

The action of tropic adenohypophyseal hormones when administered intraventricularly on rat behavioral reactions

In experiments on rats the influence was studied of tropic hormones of adenohypophysis--somatotropin, thyrotropin and adrenocorticotropin (STH, ThTN and ACTH respectively) on the elaboration and extinction of conditioned reaction of active avoidance (CRAA) in Y-maze and behaviour in the open field under microinjections of hormones into the brain lateral ventricle (0.001-0.002 ME). It has been shown that all studied hormones improve animals learning at negative pain reinforcement; ThTH and ACTH retard it in contrast to STH, which accelerates the extinction of the elaborated CRAA; tropic hormones exert differentiated influence on rats behaviour in the open field. No distinct correlation was found between behavioural manifestation and the level of catecholamines in the rats hypothalamus.     

Probability analysis of elements of rat behavior after sudden and signalled interruption of food reinforcement

Probability analysis was carried out of the appearance of single elements of rats behaviour in the process of extinction of a conditioned alimentary motor reflex. The dynamics of effector behavioural components at a sudden cessation of reinforcement (usual schedule of extinction) was compared with cessation of reinforcement signalled by a previously differentiated signal and with reinforcement cessation preceded by a stimulus initially unknown to the animal. If the reinforcement cessation is signalled by a previously differentiated (negative) stimulus, in response to its action the animals "loose the aim", what is revealed in a rapid complete reduction of all elements of the goal-directed alimentary behaviour. Obviously differentiation signal actualises the memory trace of "nonreinforcement" which was formed in the previous negative experience of the animal; this is revealed in accelerated inhibition of the alimentary motor reflex under extinction.     

Effect of previous experience in reacting to a danger signal on "open field" behavior in the rat

Modification of rats behaviour in an "hopen field" test was investigated, induced by an acoustic stimulus, previously subjected to conditioning in a shuttle chamber in experiments with possibility and impossibility of avoidance from electrical shock. It has been established that presentation of a stimulus having the meaning of a danger signal, in a new situation, significantly suppresses investigating behaviour of rats, whereas the stimulus which had not been subjected to conditioning exerts no marked effect on behaviour. The greatest suppression was observed in rats with "learned helplessness". This fact suggests that the degree of suppression of the behaviour in an open field in response to a danger signal, depends on the animal's previous experience in reacting to this signal.     

Effect of tuftsin and its analog on learning, memory and exploratory behavior in rats

On Wistar male rats the influence of tetrapeptide tuftsin and its analogue TP-1 (300 mkg/kg, i/p) on animals behaviour was studied. It is shown that administration of peptides increases the rat's exploratory activity. Activating influence of TP-1 was continued for 6 h. Daily multiple administration of tuftsin or TP-1, 15 min prior to the beginning of experiments facilitates the learning and stability of conditioned reaction with food reinforcement. Experimental animals react significantly weaker than the control ones to emotionally negative influence, produced by a sharp reduction of the amount of alimentary reinforcement control.     

Open-field behavior of rats with different levels of nervous system excitability

The dependence was studied of characteristics of organization of orienting-investigating behaviour in the open field test on the level of nervous system excitability in rats selected by the threshold of excitability of the peripheral nervous system. It is established that the studied rats lines can be divided into groups according to entropy level of their behaviour. Rats of highly excitable line build their behaviour in highly probable stereotypes as compared with the animals of low-excitable line, which organize their behaviour with more plasticity, diversity. Differences in the nervous system excitability influence first of all the organization of animals behaviour.     

Effect of 8-Br-cAMP on the formation of conditioned reflex behavior in the white rat

The influence of cAMP analogue 8-Br-cAMP on conditioning was studied in white rats. Two models of learning were used with different kinds of reinforcement, i. e. conditioned active avoidance and instrumental alimentary reactions in a complex maze. Intraventricular 8-Br-cAMP injection 4 or 24 hours before the beginning of learning improved the process of defensive as well as alimentary conditioning. Characteristics of formation of complex behaviour of experimental rats in a maze showed that under the influence of 8-Br-cAMP, not only conditioning was accelerated, but the process of optimal decision making itself was changed. The data obtained permit to suppose that 8-Br-cAMP first of all affects initially poorly learning rats.     

The effect of binocular and monocular viewing conditions on performance of rats in the Morris water maze

The visually guided behaviour in the Morris water maze (using distal extramaze cues for navigation to a small invisible platform in a large pool of opaque water) was analyzed by comparing monocular and binocular performance of hooded rats in various versions of this task. A dish-shaped metal foil occluder connected to a carrier fixed to the frontal bones was used to restrict vision to one eye. Acquisition of the water maze task with one eye occluded proceeded at the same rate as with both eyes open. There was no difference in the transfer from binocular to monocular and from monocular to binocular viewing. Retrieval of the monocularly acquired habit was equally efficient with the same as with the contralateral eye. Similar results were obtained in naive and overtrained rats. In the working memory version of the task, rats received a single acquisition trial with a new position of the escape platform followed after a delay of 2, 5, 20 or 40 min by a single retrieval trial. Performance deteriorated with increasing delay faster under interocular transfer conditions then when the same eye was used in both trials. No signs of ocular dominance were found in this task. It is concluded that successful place learning is little affected by monocular or binocular viewing conditions, but that monocular impairment becomes apparent when the difficulty of the task is increased.     

Orbital sinus blood sampling in rats: effects upon selected behavioural variables

The question addressed was whether the behaviour of rats is changed after orbital sinus blood sampling while they are under diethyl-ether anaesthesia. Twelve rats were subjected to sham anaesthesia, diethyl-ether anaesthesia and anaesthesia plus orbital puncture according to a Latin square. After each treatment, the behaviour of the rats was automatically monitored using the so-called LABORAS method, which discriminates between grooming, locomotion and inactivity. Treatment ended, and behaviour monitoring began, when the light period changed over to the dark period. The various behaviours were quantified as relative duration and frequency. Anaesthesia versus sham anaesthesia reduced the relative duration of grooming during the first 5 h after treatment. Anaesthesia plus orbital puncture versus anaesthesia alone did not significantly influence grooming, but orbital puncture did reduce the relative duration and the frequency of locomotion during the entire 20 h period, which was mainly due to a decrease in the dark period. After orbital puncture, the animals were also less frequently inactive. It is concluded that orbital puncture has an effect on behaviour superimposed on that of diethyl-ether anaesthesia. This observation may contribute new arguments to the debate on the acceptability of the orbital puncture technique.     

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.     

Effects of prenatal stress on lever-press acquisition with delayed reinforcement in male and female rats

The prenatally stressed (PS) rat shows enhanced conditioned fear and increased behavioral inhibition in response to footshock compared to control (CON) rats. It is unclear whether this facilitated learning will occur only with aversive stimulation, or if it will also be observed in the context of positive reinforcement. There are limited and inconsistent data regarding sex differences and the impact of prenatal stress on learning. The present study was designed to examine lever-press acquisition with a 10-s delay to food reinforcement in male and female PS and CON rats. Overall, twice as many PS male rats acquired the lever-press response than the PS female rats, CON male rats, and CON female rats. PS male rats also earned significantly more reinforcers and responded on the operative lever at a significantly greater rate than the other three rat groups. These findings suggest that PS rats exhibit altered learning with a task involving positive reinforcement, and this effect of PS is sex specific for male rats.     

Differences in behavior of impulsive and self-controlled rats in the open-field and light-dark tests

The aim of the study was to reveal the relationship between impulsive behavior in rats, on the one hand, and locomotor activity and emotionality on the other hand. Rats were divided into groups according to their preference for reinforcements of different values. Animals that preferred valuable but delayed reinforcement in more than 60% of cases formed a self-controlled group, whereas rats that selected poor but immediate reinforcements in more than 60% of the cases were considered as impulsive. The two groups of animals were subjected to the "open field" and "light-dark" tests. The impulsive animals more quickly adapted to new surroundings and displayed more pronounced research activity as compared to the self-controlled animals. The level of anxiety was higher in the self-controlled group.