Spatial-motor asymmetry in rat behavior

The experiments were carried out on rats in three different mazes: U-shape, complicated linear and 12-beam radial. Series of tests differed by succession of rats learning in the mazes and the character of reinforcement. Most of the rats manifested a spatial-motor asymmetry (SMA) in all used situations. Under all conditions SMA increased in the process of learning parallel to a decrease of the errors number or the time of the task performing. In the group of rats sequently learning in different mazes, the direction of moving changed with changes in spatial characteristics of the medium. Preliminary training of rats in conditions creating SMA, promoted its acceleration in new conditions. The conclusion is made that the rats have no physiological mechanism which rigidly fixes a single (in all conditions) direction of runs. SMA is considered as a behavioural tactics which is corrected in the process of training and which provides for an adequate behaviour.     

Neural substrates of sensory-guided locomotor decisions in the rat superior colliculus

Deciding in which direction to move is a ubiquitous feature of animal behavior, but the neural substrates of locomotor choices are not well understood. The superior colliculus (SC) is a midbrain structure known to be important for controlling the direction of gaze, particularly when guided by visual or auditory cues, but which may play a more general role in behavior involving spatial orienting. To test this idea, we recorded and manipulated activity in the SC of freely moving rats performing an odor-guided spatial choice task. In this context, not only did a substantial majority of SC neurons encode choice direction during goal-directed locomotion, but many also predicted the upcoming choice and maintained selectivity for it after movement completion. Unilateral inactivation of SC activity profoundly altered spatial choices. These results indicate that the SC processes information necessary for spatial locomotion, suggesting a broad role for this structure in sensory-guided orienting and navigation.     

Effects of testosterone and estradiol on serum somatomedin A and growth rate of rats

The mode of involvement of sex steroids in the growth spurt during adolescence was studied in Wistar rats with a special reference to the level of serum somatomedin A (SMA) determined by radioreceptor assay. Intramuscular administration of testosterone propionate (T; 1 mg/day, alternately for 10 days) to female or gonadectomized male rats provoked a small but significant increase in their body weight or body length without affecting the serum SMA level. In contrast, in hypophysectomized (hypox) male rats T caused a considerable increase in body weight and the serum SMA level only when administered concurrently with bovine growth hormone (bGH; 0.2 U/day, ip). T did not affect the sulfation activity in vitro. These results suggest that androgen participates in the growth spurt during adolescence by enhancing the SMA effect and/or potentiating the SMA production by GH. Estradiol benzoate (E2; 100 micrograms/day, alternately for 10 days) caused a decrease in the serum SMA level and the growth rate in normal male rats. However, E2 produced an increase in the SMA level when administered to hypox male rats, although the growth was retarded and sulfation potency of the serum was sharply reduced. These results indicate that E2 may suppress the growth by lowering SMA generation in normal rats and cause a production of biologically inactive SMA in hypox male rats.     

Speed/accuracy trade-off between the habitual and the goal-directed processes

Instrumental responses are hypothesized to be of two kinds: habitual and goal-directed, mediated by the sensorimotor and the associative cortico-basal ganglia circuits, respectively. The existence of the two heterogeneous associative learning mechanisms can be hypothesized to arise from the comparative advantages that they have at different stages of learning. In this paper, we assume that the goal-directed system is behaviourally flexible, but slow in choice selection. The habitual system, in contrast, is fast in responding, but inflexible in adapting its behavioural strategy to new conditions. Based on these assumptions and using the computational theory of reinforcement learning, we propose a normative model for arbitration between the two processes that makes an approximately optimal balance between search-time and accuracy in decision making. Behaviourally, the model can explain experimental evidence on behavioural sensitivity to outcome at the early stages of learning, but insensitivity at the later stages. It also explains that when two choices with equal incentive values are available concurrently, the behaviour remains outcome-sensitive, even after extensive training. Moreover, the model can explain choice reaction time variations during the course of learning, as well as the experimental observation that as the number of choices increases, the reaction time also increases. Neurobiologically, by assuming that phasic and tonic activities of midbrain dopamine neurons carry the reward prediction error and the average reward signals used by the model, respectively, the model predicts that whereas phasic dopamine indirectly affects behaviour through reinforcing stimulus-response associations, tonic dopamine can directly affect behaviour through manipulating the competition between the habitual and the goal-directed systems and thus, affect reaction time.     

Bursts and Heavy Tails in Temporal and Sequential Dynamics of Foraging Decisions

A fundamental understanding of behavior requires predicting when and what an individual will choose. However, the actual temporal and sequential dynamics of successive choices made among multiple alternatives remain unclear. In the current study, we tested the hypothesis that there is a general bursting property in both the timing and sequential patterns of foraging decisions. We conducted a foraging experiment in which rats chose among four different foods over a continuous two-week time period. Regarding when choices were made, we found bursts of rapidly occurring actions, separated by time-varying inactive periods, partially based on a circadian rhythm. Regarding what was chosen, we found sequential dynamics in affective choices characterized by two key features: (a) a highly biased choice distribution; and (b) preferential attachment, in which the animals were more likely to choose what they had previously chosen. To capture the temporal dynamics, we propose a dual-state model consisting of active and inactive states. We also introduce a satiation-attainment process for bursty activity, and a non-homogeneous Poisson process for longer inactivity between bursts. For the sequential dynamics, we propose a dual-control model consisting of goal-directed and habit systems, based on outcome valuation and choice history, respectively. This study provides insights into how the bursty nature of behavior emerges from the interaction of different underlying systems, leading to heavy tails in the distribution of behavior over time and choices.     

Infection of male rats with Toxoplasma gondii results in enhanced delay aversion and neural changes in the nucleus accumbens core

Rats infected with the protozoan parasite Toxoplasma gondii exhibit reduced avoidance of predator odours. This behavioural change is likely to increase transmission of the parasite from rats to cats. Here, we show that infection with T. gondii increases the propensity of the infected rats to make more impulsive choices, manifested as delay aversion in an intertemporal choice task. Concomitantly, T. gondii infection causes reduction in dopamine content and neuronal spine density of the nucleus accumbens core, but not of the nucleus accumbens shell. These results are consistent with a role of the nucleus accumbens dopaminergic system in mediation of choice impulsivity and goal-directed behaviours. Our observations suggest that T. gondii infection in rats causes a syndromic shift in related behavioural constructs of innate aversion and making foraging decisions.     

Acute effect of induced asymmetrical running technique on foot skin temperature

The aim of the study was to evaluate skin temperature of the soles of the feet before and after a provoked asymmetrical running. Seventeen recreational male runners performed two 15 min running tests in the same session. In the first test, participants performed running without modifying their running technique (control condition). In the second running test, they repeated the same protocol using an ankle weight of 1.5 kg in the non-dominant ankle (asymmetrical condition). Rate of perceive exertion, heart rate and spatio-temporal parameters were measured during the running tests. Skin temperature was measured with an infrared camera before and after each condition. Generally, comparing both lower limbs, non-preferred limb (with the ankle weight) had lower contact time (p < 0.001 and ES > 0.8), higher stride length (p < 0.05 and ES > 0.3) and higher stride frequency in asymmetrical condition (p < 0.01 and ES > 0.4). However, no differences were observed on skin temperature between both feet in the two conditions in any of the regions of interest assessed (p > 0.05). Although the asymmetry generation model used provoked technical asymmetries in spatio-temporal parameters during running, no thermal asymmetries were observed between preferred and non-preferred sole of the foot. These results suggested the lower importance of mechanical than physiological mechanisms on skin temperature during running.     

Avoidance reaction and defensive reflex in the rabbit based on hypothalamic stimulation inducing strokes of the paws

In experiments on rabbits electrical stimulation of the medial hypothalamic area elicited a biphasic reaction: running during the current action and species-specific reaction of kicking the floor with the hind limbs in poststimulous period. Conditioning with acoustic stimulus led in the half of rabbits to elaboration of a habit of jumping on a safe platform in experimental model of active avoidance and to a weak conditioned reaction of kicking without running in the model of classical defensive reflex. The number of conditioned limb kicks was 7-10 times less than that of analogous responses to the reinforcing stimulus. With the increase of the number of combinations, the conditioned habit of kicking became deteriorated: the response became weaker and its latency more prolonged. The results of experiments are discussed in the light of Anokhin's theory of functional system of goal-directed behavioural act.     

The role of kinaesthetic feedback in goal-directed movements

The purpose of this study was to investigate the role of kinaesthetic feedback in the control of goal-directed movements. The subjects were qualified basketball and handball players compared to weightlifters as controls. The body measures and the general motor tests verified fit physical condition of the subjects, and detected no sign that would disturb the execution of special motor tests. The special motor tests were free-throw shootings with basketball to the basket, free shootings with handball to a rectangular frame, zigzag dribbling with basketball to 14 m among traffic cones 2 m apart, and stopping at a mark after running to 10 m. These tests were performed both with open eyes and closed eyes. The results of all special motor tests decreased significantly in the lack of visual information. Furthermore, in contrast to the significantly different results obtained from the three different groups with open eyes, these groups produced equally minor results with closed eyes. It is concluded that the practice of goal-directed movement, learned under visual guidance, does not make the kinaesthetic feedback able to compensate the lack of visual input.     

Behavioral interactions in cocaine-treated rats

Effects of a single dose of cocaine (10 mg/kg,i.p.) were studied on spontaneous motor activity (SMA), stereotypy. self-stimulation of the posterior hypothalamus or area ventralis tegmentum (A10 area) and nonreinforced bar-pressing in rats. Interactions among these behaviors were investigated under different experimental designs. Cocaine caused an initial increase of SMA, which was later decreased significantly, as stereotypy became more prominent. Cocaine also caused facilitation of self-stimulation responding that further increased SMA. In both groups of self-stimulating rats, stereotypy disappeared completely during self-stimulation. Following cessation of self-stimulation, SMA and bar-pressing (that became nonreinforced) decreased, and stereotypy reappeared in both groups of rats.     

Measurement of spontaneous motor activity by using the vibrator response method in rats

To investigate the usefulness of spontaneous motor activity (SMA) measurement using the vibrator response method, the acute effects of drugs on SMA were observed in Sprague-Dawley male rats. There were no significant differences between four devices. Methamphetamine (0.3-1 mg/kg, i.p.) and 1-2 mg/kg (s.c.) of apomorphine increased the SMA, but 0.05-0.2 mg/kg (s.c.) of apomorphine decreased the SMA. Apomorphine at 1-2 mg/kg (s.c.) significantly increased the SMA when the vibrator response method was used as compared with the Animex method. These results suggest that the vibrator response apparatus is useful for the measurement of SMA in rats.     

Effects of endurance moderate physical training on basal metabolism of young adult rats

In order to clarify the conclusion that the change of basal metabolism affected by physical training, effect of endurance training for 8 weeks on basal metabolism of young adult rats were investigated. Results are as follows. Endurance training increased significantly running ability of rats, for instance the running time at a speed of 25 m/min on the control and training groups were 53.7 +/- 18.8 min, 232.8 +/- 32.8 min, respectively. The ratio of soleus's weight to the body weight in trained rats was high significantly (p less than 0.05). The glycogen contents of trained rats under the condition of feeding have higher than the control rats. Especially, glycogen contents of the soleus and red-gastrocnemius significant increased (p less than 0.05), and liver glycogen content under the same condition increased significantly (p less than 0.02). The oxygen consumption in trained rats increased significantly compared with control rats (p less than 0.03). The basal metabolism of trained rats showed 1.24-fold increase compared with those of control (p less than 0.02). Oxygen consumption of sliced ventricle in trained rats increased significantly (p less than 0.03), it's rate was 118% of control. However those of other tissues did not change significantly.     

Gait asymmetry: composite scores for mechanical analyses of sprint running

Gait asymmetry analyses are beneficial from clinical, coaching and technology perspectives. Quantifying overall athlete asymmetry would be useful in allowing comparisons between participants, or between asymmetry and other factors, such as sprint running performance. The aim of this study was to develop composite kinematic and kinetic asymmetry scores to quantify athlete asymmetry during maximal speed sprint running. Eight male sprint trained athletes (age 22±5 years, mass 74.0±8.7 kg and stature 1.79±0.07 m) participated in this study. Synchronised sagittal plane kinematic and kinetic data were collected via a CODA motion analysis system, synchronised to two Kistler force plates. Bilateral, lower limb data were collected during the maximal velocity phase of sprint running (velocity=9.05±0.37 ms(-1)). Kinematic and kinetic composite asymmetry scores were developed using the previously established symmetry angle for discrete variables associated with successful sprint performance and comparisons of continuous joint power data. Unlike previous studies quantifying gait asymmetry, the scores incorporated intra-limb variability by excluding variables from the composite scores that did not display significantly larger (p<0.05) asymmetry than intra-limb variability. The variables that contributed to the composite scores and the magnitude of asymmetry observed for each measure varied on an individual participant basis. The new composite scores indicated the inter-participant differences that exist in asymmetry during sprint running and may serve to allow comparisons between overall athlete asymmetry with other important factors such as performance.     

Influence of acute physical exercise on glutathione and lipid peroxides in blood of rat and man

In rats physical exercise (30 min running on a treadmill) lowered total glutathione, oxidized glutathione and lipid peroxide concentration in blood. In man (young healthy male volunteers, moderate to excellent physical condition) running (30 min) did not influence these parameters. It is concluded that by normal life and psychophysical vigilance the moderate oxidative stress could be compensated.     

Renal epithelial proliferation and its clinical expression in Brown Norway (BN) rats

Renal epithelial proliferation has previously been found to be a common condition in a colony of Lewis x Brown Norway (BN) F2 hybrid rats. The aim of this study was to investigate the prevalence and clinical consequences of this condition in pure inbred BN and Lewis rats. Renal epithelial proliferation was found in 29 of 49 BN rats (59%) examined and in four of 50 Lewis rats (8%) examined. Serum creatinine and serum corticosterone was not influenced by the condition. Haematuria was more common in BN rats with (74%) than without renal papillary proliferation (35%, P < 0.05), but it may not be used to diagnose renal epithelial proliferation, as we found rats having renal epithelial proliferation without showing haematuria and rats showing haematuria without having renal epithelial proliferation. Haematuria was also common in Lewis rats (16-56% dependent of age and gender), in which renal epithelial proliferation were found in only 8%. Fluctuating asymmetry, which was used as a measure of developmental instability, was found to be increased in rats with renal epithelial proliferation (P < 0.05). Haematuria was also found to be related to the degree of fluctuating asymmetry (P < 0.01). Although the prevalence of renal epithelial proliferation is clearly higher in BN rats than in Lewis rats (P < 0.01), and although in previous reports the condition was found in F2 BN x Lewis hybrids and not in F1 BN x Lewis hybrids it cannot clearly be defined as having been caused by a single Mendelian gene, as we found it in both inbred strains. Futhermore, we found that morphologically the proliferations could be placed on the papillary as well as the medullary wall of the renal pelvis, while previously it has only been described on the papillary wall.     

Asymmetry of movement direction as a tactic in the feeding behavior of rats

The sign and degree of spatial-motor asymmetry in rats were studied in conditions both of spontaneous or signalled choice in an U-maze and spontaneous multiple choice in a radial labyrinth. It was shown that during investigation of a new environment, motor asymmetry in rats was feebly expressed in all conditions of experiments, irrespective of the labyrinth scheme and experimental procedures. In the process of training, adequate behaviour was formed and in some conditions a distinctly expressed spatial asymmetry appeared, while in other cases it was absent. Apparently, while investigating an "unknown" situation (where rats can move rightwards and leftwards), the strategy of "displacement" is characteristic of them. Later the rate of asymmetry manifestation depends on concrete spatial and temporal characteristics of already "familiar" surroundings.     

Hemispheric asymmetry of the nigrostriatal system of the brain in rats genetically predisposed to catalepsy]

Hemispheric asymmetry of nigro-striate system in a strain of rats GC bred from Wistar for a predisposition to cataleptic reaction was studied by means of biochemical and morphological methods. Hemispheric asymmetry was found in GC and Wistar rats with respect to aminopeptidase activity in neurons of caudate nucleus, with a more pronounced left-side increase in GC rats, the asymmetry index being 13.7%. Acetylcholine esterase activity in subcellular particles of caudate nucleus showed an inversion of asymmetry with higher activity in the left hemisphere of Wistar and right hemisphere of GC rats, and asymmetry index of 15.5%. With respect to the number of astroglia cells in S. nigra, and astroglia and oligodendroglia in N. accumbens there was also an inversion of asymmetry in GC rats who had more cells in the structures of the left hemisphere, whereas Wistar rats had more in the right hemisphere. The asymmetry index was high and equal to 29.8% for astroglia in S. nigra, and 17% for astroglia and 21.4% for oligodendroglia in N. accumbens. However, in S. nigra the number of neurons and oligodendroglia cells was equally increased in the right hemisphere in GC and Wistar rats. The data suggest that the mechanism of hereditary pathology of brain nigro-striate system involves both enhancement and inversion of the hemispheric asymmetry.     

Actions,Action Sequences and Habits: Evidence That Goal-Directed and Habitual Action Control Are Hierarchically Organized

Behavioral evidence suggests that instrumental conditioning is governed by two forms of action control: a goal-directed and a habit learning process. Model-based reinforcement learning (RL) has been argued to underlie the goal-directed process; however, the way in which it interacts with habits and the structure of the habitual process has remained unclear. According to a flat architecture, the habitual process corresponds to model-free RL, and its interaction with the goal-directed process is coordinated by an external arbitration mechanism. Alternatively, the interaction between these systems has recently been argued to be hierarchical, such that the formation of action sequences underlies habit learning and a goal-directed process selects between goal-directed actions and habitual sequences of actions to reach the goal. Here we used a two-stage decision-making task to test predictions from these accounts. The hierarchical account predicts that, because they are tied to each other as an action sequence, selecting a habitual action in the first stage will be followed by a habitual action in the second stage, whereas the flat account predicts that the statuses of the first and second stage actions are independent of each other. We found, based on subjects'' choices and reaction times, that human subjects combined single actions to build action sequences and that the formation of such action sequences was sufficient to explain habitual actions. Furthermore, based on Bayesian model comparison, a family of hierarchical RL models, assuming a hierarchical interaction between habit and goal-directed processes, provided a better fit of the subjects'' behavior than a family of flat models. Although these findings do not rule out all possible model-free accounts of instrumental conditioning, they do show such accounts are not necessary to explain habitual actions and provide a new basis for understanding how goal-directed and habitual action control interact.     

A comparative analysis of learning and exploratory behavior in rats with different resistances to stress exposures and to the brain monoamine level]

Wistar rats stable (S) to sound stimulus differed from the unstable (NS) ones by a heightened investigatory activity in condition of moderate stress in the open field test, by heightened reactivity to sensory stimuli of various modalities (somatosensory, visual and olfactory), lowered level of investigatory behaviour in the test of burrow chamber. S-rats differed from NS-animals by a higher ability to learning of goal-directed reaction and a lower ability to discrimination of different emotional influences. The results of biochemical analysis of the content of biogenic amines in various brain structures revealed in stable rats an increase of noradrenaline level and in non-stable ones--a higher level of dopamine and serotonin.     

Food-procuring skill in rats: prolongations of the extension phase in final movements of right-handed rats

In Wistar rats with different forepaw preference trained to get food spheres from a narrow horizontal tube feeder, the duration of the paw extension phase was studied in both preliminary and final (successful) food-procuring movements. In left-handed rats, the paw extension was fastly in both preliminary and final movements than in right-handed animals. In right-handed animals, the extension phase of the final successful movements was much slower than that of preliminary movements, whereas in left-handed rats the slowing of the final extension was poorly expressed. The prolongation of the extension phase suggests a possibility of correction of the extension phase of the goal-directed movements