Operant conditioning of rat navigation using electrical stimulation for directional cues and rewards

Operant conditioning is often used to train a desired behavior in an animal. The contingency between a specific behavior and a reward is required for successful training. Here, we compared the effectiveness of two different mazes for training turning behaviors in response to directional cues in Sprague-Dawley rats. Forty-three rats were implanted with electrodes into the medial forebrain bundle and the left and right somatosensory cortices for reward and cues. Among them, thirteen rats discriminated between the left and right somatosensory stimulations to obtain rewards. They were trained to learn ipsilateral turning response to the stimulation of the left or right somatosensory cortex in either the T-maze (Group T) or the maze (Group W). Performance was measured by the navigation speed in the mazes. Performances of rats in Group T were enhanced faster than those in Group W. A significant correlation between performances during training and performance in final testing was observed in Group T starting with the fifth training session while such a correlation was not observed in Group W until the tenth training session. The training mazes did not however affect the performances in the final test. These results suggest that a simple maze is better than a complicated maze for training animals to learn directions and direct cortical stimulation can be used as a cue for direction training.     

Learning large-scale spatial relationships in a maze and effects of MK-801 on retrieval in the rhesus monkey

Monkeys have strong abilities to remember the visual properties of potential food sources for survival in the nature. The present study demonstrated the first observations of rhesus monkeys learning to solve complex spatial mazes in which routes were guided by visual cues. Three monkeys were trained in a maze (6 m x 6 m) included of four different mazes. We recorded the cue and cup errors, latencies, and pathway for each trial. The data showed that monkeys learned the target place after three days in the first maze and spent a shorter time in learning the following mazes. The maze was an efficient method to measure the ability and proceeding of spatial memory in monkeys. Moreover, working memory can also be tested by using the maze. MK-801 at 0.02 mg/kg but not at 0.005 mg/kg impaired monkeys' retrieval of spatial memory after they learned all four mazes. The present maze may provide an efficient method to help bridging the gap in cognition between nonhuman primates and humans, and in particular to gain insight into human cognitive function and dysfunction.     

Changes in the learning ability of epiphysectomized rats

The experiments on rats have shown changes in the learning ability of animals. The learning of locomotor reactions of escape and avoidance conditioned reflex was accelerated in animals after pinealectomy. Training of rats in U-shaped and 16-door mazes was significantly affected after pinealectomy. The index of reflex retention (1 and 7 days later) was not changed in the operated animals. Epithalamin (0.5 mg/kg for 5 days) selectively facilitated learning of visual and space discrimination.     

Barnes Maze Testing Strategies with Small and Large Rodent Models

Spatial learning and memory of laboratory rodents is often assessed via navigational ability in mazes, most popular of which are the water and dry-land (Barnes) mazes. Improved performance over sessions or trials is thought to reflect learning and memory of the escape cage/platform location. Considered less stressful than water mazes, the Barnes maze is a relatively simple design of a circular platform top with several holes equally spaced around the perimeter edge. All but one of the holes are false-bottomed or blind-ending, while one leads to an escape cage. Mildly aversive stimuli (e.g. bright overhead lights) provide motivation to locate the escape cage. Latency to locate the escape cage can be measured during the session; however, additional endpoints typically require video recording. From those video recordings, use of automated tracking software can generate a variety of endpoints that are similar to those produced in water mazes (e.g. distance traveled, velocity/speed, time spent in the correct quadrant, time spent moving/resting, and confirmation of latency). Type of search strategy (i.e. random, serial, or direct) can be categorized as well. Barnes maze construction and testing methodologies can differ for small rodents, such as mice, and large rodents, such as rats. For example, while extra-maze cues are effective for rats, smaller wild rodents may require intra-maze cues with a visual barrier around the maze. Appropriate stimuli must be identified which motivate the rodent to locate the escape cage. Both Barnes and water mazes can be time consuming as 4-7 test trials are typically required to detect improved learning and memory performance (e.g. shorter latencies or path lengths to locate the escape platform or cage) and/or differences between experimental groups. Even so, the Barnes maze is a widely employed behavioral assessment measuring spatial navigational abilities and their potential disruption by genetic, neurobehavioral manipulations, or drug/ toxicant exposure.     

Conflict as a determinant of rat behavior in three types of elevated plus-maze

Three groups of rats were tested in different types of elevated plus-mazes, a normal one (two closed and two open arms), a totally closed one (four closed arms) and a totally open (four open arms). Closed arms were surrounded by 40-cm high wooden walls and open arms were surrounded by 0.5-cm high transparent Plexiglas ledges. As expected, in the closed maze rats explored equally all the arms, both in terms of time and frequency of entries, as well as in exploration of the extremities. Rats in the totally open maze also presented a similar pattern of exploration, that is, no significant differences were found between the results obtained with the closed and the open mazes in terms of central and extremities exploration. It is suggested that the typical behavior of rats in the conventional elevated plus-maze is caused by the contrasting characteristics of open and closed arms rather than by the physical aversive characteristics of the open arms per se. Results also confirm a prediction made by a computer model simulating rat exploratory behavior in virtual mazes, normal, totally open and totally closed.     

Motor learning in man: A review of functional and clinical studies

This chapter reviews results of clinical and functional imaging studies which investigated the time-course of cortical and subcortical activation during the acquisition of motor a skill. During the early phases of learning by trial and error, activation in prefrontal areas, especially in the dorsolateral prefrontal cortex, is has been reported. The role of these areas is presumably related to explicit working memory and the establishment of a novel association between visual cues and motor commands. Furthermore, motor associated areas of the right hemisphere and distributed cerebellar areas reveal strong activation during the early motor learning. Activation in superior-posterior parietal cortex presumably arises from visuospatial processes, while sensory feedback is coded in the anterior-inferior parietal cortex and the neocerebellar structures. With practice, motor associated areas of the left-hemisphere reveal increased activity. This shift to the left hemisphere has been observed regardless of the hand used during training, indicating a left-hemispheric dominance in the storage of visuomotor skills. Concerning frontal areas, learned actions of sequential character are represented in the caudal part of the supplementary motor area (SMA proper), whereas the lateral premotor cortex appears to be responsible for the coding of the association between visuo-spatial information and motor commands. Functional imaging studies which investigated the activation patterns of motor learning under implicit conditions identified for the first, a motor circuit which includes lateral premotor cortex and SMA proper of the left hemisphere and primary motor cortex, for the second, a cognitive loop which consists of basal ganglia structures of the right hemisphere. Finally, activity patterns of intermanual transfer are discussed. After right-handed training, activity in motor associated areas maintains during performance of the mirror version, but is increased during the performance of the original-oriented version with the left hand. In contrary, increased activity during the mirror reversed action, but not during the original-oriented performance of the untrained right hand is observed after left-handed training. These results indicate the transfer of acquired right-handed information which reflects the mirror symmetry of the body, whereas spatial information is mainly transferred after left-handed training. Taken together, a combined approach of clinical lesion studies and functional imaging is a promising tool for identifying the cerebral regions involved in the process of motor learning and provides insight into the mechanisms underlying the generalisation of actions.     

Influence of acoustic signal with ultrasonic components on the development of defensive conditioned reflex in Wistar rats

Short-term (90 s) effects of the complex acoustic signal (CAS) with ultrasonic components on the development of defensive conditioned reflex of two-way active avoidance in a shuttle-box were studied in female Wistar rats. The learning ability of rats was measured on a scale designed in our laboratory. It was shown that CAS stimulation triggered an audiogenic seizure of different strength in 59% of animals. The CAS was extremely stressful for Wistar rats: it prevented the active avoidance learning in early terms after its application (the first training session in 4 or 6 days). This effect did not depend on the presence or intensity of audiogenic seizures during CAS. In the second training session in 9 days (the first session was in 4 days), learning was impaired as compared to control without CAS. However, during repeated training procedure 1.5 months after the CAS (the first session in 6 days), rats rapidly reached the criterion of learning (10 consecutive avoidance reactions). On the other hand, if the CAS was presented with different time lags (immediately, in 3 or in 45 days) after the first training session, the ability of animals to learn during the second session was not impaired both in early and late terms after exposure to the stressor. The results suggest that exposure to CAS prevents development of short-term memory but does not affect consolidation process and long-term memory.     

Female guppies Poecilia reticulata prefer males that can learn fast

The role of learning ability as a potentially desirable male trait in sexual selection was investigated in the guppy Poecilia reticulata . Mate preference tests and the rate at which a male learnt two mazes were used to determine whether female preference was related to male learning ability. In addition, male body size and saturation of the orange patches were measured. Female preference was found to be related to rate of learning, such that males that learnt the mazes faster were found to be more attractive to females, but was not found to be related to body size or saturation.     

Le comportement du Chevrotain africain,Hyemoschus aquaticus Ogilby (Artiodactyla,Ruminantia)

The purpose of this study was to test the influence of social isolation during infancy on learning behavior in rats. Rats, reared isolated (n = 55) or paired (n = 60) for a period of 50 days following weaning, were tested on different learning tasks in an operant conditioning chamber. Isolation rearing produced significantly better learning when the training period directly followed the different housing conditions. After a 28 day period of social isolation for the subjects raised paired during infancy no differences in learning between isolated and paired reared animals could be observed. The differences are discussed in relation to the effects of stimulus deprivation.     

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.     

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.     

Developmental Lead Exposure and Two-Way Active Avoidance Training Alter the Distribution of Protein Kinase C Activity in the Rat Hippocampus

Long-term exposure to a low level of lead is associated with learning deficits. Several types of learning have been correlated to hippocampal protein kinase C (PKC) activation. This study was designed to determine if there is a correlation between the effects of lead on hippocampal PKC activation and those on learning performance. Rats were exposed to 0.2% (w/v) lead acetate at different developmental stages including a maternally exposed group, a postweaning exposed group, and a continuously exposed group. The continuously lead exposed rats tended to avoid less frequently and not respond more frequently in two-way active avoidance training than did controls. This training process was associated with translocation of hippocampal PKC activity from cytosol to membrane. Two-way analysis of variance of data indicates that there is a significant training and lead treatment interaction in the ratio of membrane to cytosolic PKC activity (F_3,32 = 3.013; p = 0.044). The interaction is attributable to the absence of the training-induced PKC translocation in the continuously lead exposed rats. In addition, no significant changes were observed in learning performance and training-induced hippocampal PKC activation after maternal and postweaning lead exposure. Continuous and longer duration of lead exposure appears to affect the learning performance and hippocampal PKC activation. These data suggest that a change in the activation of hippocampal PKC may be involved in the lead-induced deficit in learning.     

Comparative characteristics of psychoemotional patterns in Albino and Wistar rats

Analysis of psychoemotional behavioral component in Albino and Wistar rats during solving a cognitive task showed that intra-population differences were determined by the relationship between passive and active forms of unconditioned reactions. Quick-learning rats from both populations were characterized by the dominance of active forms of psychoemotional reactions over the course of training. The learning process in slow-learning rats was accompanied mainly by passive emotional manifestations, whereas active reactions dominated at the stage of habit realization. Passive forms of manifestations prevailed over active forms over the course of training in both Albino and Wistar rats which failed to solve the task. The interpopulational psychoemotional differences were quantitative and depended only on the learning styles. Wistar strain was characterized by a decreased percent of animals which were able to solve a cognitive task (40% versus 80% in Albino rats), affective flatness and decreased tolerance to information loadings.     

Optimizing action of synthetic peptide Selank on active avoidance conditioning test in rats

The action of a synthetic peptide Selank on learning and memory in active avoidance conditioning test was studied in rats with initially low learning ability and normal animals. The peptide was administered repeatedly 15 min prior the training session (4 days). The effect of Selank (300 micrograms/kg) was compared to that of Pyracetam (400 mg/kg). Selank was found to significantly improve learning in rats with low level ability even after a single administration on the first day of training session. The effect progressively increased with repeated Selank treatment: the total numbers of reactions and correct reactions increased, and the number of errors decreased (p < 0.05). In normal rats, the effect was maximal on the third day of treatment and training, i.e., after the completed initial consolidation. Some distinguishing features were revealed in the dynamics of activatory effects of Selank and Pyracetam. These data together with the evidence for ansiolytic effect of Selank show that this drug is promising for optimization of mnestic functions under conditions of high emotional stress.     

Study of the role of different types of glutamate receptors in spatial memory in rats]

A comparative study was performed to assess effects of different antagonists of glutamate receptors on spatial discrimination of rats in 8-arm radial and water mazes. Noncompetitive NMDA receptor blocker MK-801 in the dose 0.10 mg/kg and higher impaired the accuracy of performance in radial maze, whereas in the doses 0.05--0.30 mg/kg in water maze. Quisqualate IAMPA- and 2-amino-4-phosphonobutyrate (2-APB) I antagonists glutamate diethyl ester (250--500 mg/kg) and 2-APB (50--100 mg/kg), respectively, only increased time to complete radial maze performance and failed to alter choice accuracy. Both antagonists at the same doses did not affect performance of water maze task. The involvement of each type of glutamate receptors in different stages of spatial discrimination process in rats was discussed.     

The effect of altered selenium and vitamin E nutritional status on learning and memory of third-generation rats

It has been proposed that selenium (Se) and Vitamin E (Vit E) are involved synergistically in protection of cell membrane lipids from peroxidation. However, little is known about the effect of both deficiencies of Se and Vit E and toxic status of those antioxidants on the peroxidation potentiality of the brain. We aimed to study the effects of both Se and Vit E inadequate diet and Se rich diet on the learning and memory processes of third-generation young rats. Their ancestors were also fed by the same diets starting from their births. To test the learning and memory, the rats aged 60 days were trained by using automated two ways active avoidance shuttle box. The acquisition tests were terminated with training the rat from each group to be 25 trials per day during three days. Ten days after the last acquisition test, the retention test was performed and the acquisition of the conditioned avoidance responses (CAR) of the rats were evaluated. It is demonstrated that the CAR of all rats from three groups showed a significant increase in three consecutive days while the differences observed in CAR of same sessions was not significantly different among three groups. The memory process of these young rats also was not affected significantly by two types of diets. Under the light of our results one can suggest that, in the case of alterations in antioxidant defense status, the learning and the memory mechanisms seems to be not affected. Further researches are needed to be able to explain the possible role of oxidative stress on the mechanisms of learning and memory.     

A robust deep attention dense convolutional neural network for plant leaf disease identification and classification from smart phone captured real world images

Plant diseases cause significant food loss and hence economic loss around the globe. Therefore, automatic plant disease identification is a primary task to take proper medications for controlling the spread of the diseases. Large variety of plants species and their dissimilar phytopathological symptoms call for the implementation of supervised machine learning techniques for efficient and reliable disease identification and classification. With the development of deep learning strategies, convolutional neural network (CNN) has paved its way for classification of multiple plant diseases by extracting rich features. However, several characteristics of the input images especially captured in real world environment, viz. complex or indistinguishable background, presence of multiple leaves with the diseased leaf, small lesion area, solemnly affect the robustness and accuracy of the CNN modules. Available strategies usually applied standard CNN architectures on the images captured in the laboratory environment and very few have considered practical in-field leaf images for their studies. However, those studies are limited with very limited number of plant species. Therefore, there is need of a robust CNN module which can successfully recognize and classify the dissimilar leaf health conditions of non-identical plants from the in-field RGB images. To achieve the above goal, an attention dense learning (ADL) mechanism is proposed in this article by merging mixed sigmoid attention learning with the basic dense learning process of deep CNN. The basic dense learning process derives new features at higher layer considering all lower layer features and that provides fast and efficient training process. Further, the attention learning process amplifies the learning ability of the dense block by discriminating the meaningful lesion portions of the images from the background areas. Other than adding an extra layer for attention learning, in the proposed ADL block the output features from higher layer dense learning are used as an attention mask to the lower layers. For an effective and fast classification process, five ADL blocks are stacked to build a new CNN architecture named DADCNN-5 for obtaining classification robustness and higher testing accuracy. Initially, the proposed DADCNN-5 module is applied on publicly available extended PlantVillage dataset to classify 38 different health conditions of 14 plant species from 54,305 images. Classification accuracy of 99.93% proves that the proposed CNN module can be used for successful leaf disease identification. Further, the efficacy of the DADCNN-5 model is checked after performing stringent experiments on a new real world plant leaf database, created by the authors. The new leaf database contains 10,851 real-world RGB leaf images of 17 plant species for classifying their 44 distinguished health conditions. Experimental outcomes reveal that the proposed DADCNN-5 outperforms the existing machine learning and standard CNN architectures, and achieved 97.33% accuracy. The obtained sensitivity, specificity and false positive rate values are 96.57%, 99.94% and 0.063% respectively. The module takes approximately 3235 min for training process and achieves 99.86% of training accuracy. Visualization of Class activation mapping (CAM) depicts that DADCNN-5 is able to learn distinguishable features from semantically important regions (i.e. lesion regions) on the leaves. Further, the robustness of the DADCNN-5 is established after experimenting with augmented and noise contaminated images of the practical database.     

Stages of motor skill learning

Successful learning of a motor skill requires repetitive training. Once the skill is mastered, it can be remembered for a long period of time. The durable memory makes motor skill learning an interesting paradigm for the study of learning and memory mechanisms. To gain better understanding, one scientific approach is to dissect the process into stages and to study these as well as their interactions. This article covers the growing evidence that motor skill learning advances through stages, in which different storage mechanisms predominate. The acquisition phase is characterized by fast (within session) and slow learning (between sessions). For a short period following the initial training sessions, the skill is labile to interference by other skills and by protein synthesis inhibition, indicating that consolidation processes occur during rest periods between training sessions. During training as well as rest periods, activation in different brain regions changes dynamically. Evidence for stages in motor skill learning is provided by experiments using behavioral, electrophysiological, functional imaging, and cellular/molecular methods.     

The hippocampus and flexible spatial knowledge in rats

Lesions to the hippocampal system in rats result in a profound impairment of place or locale spatial learning although other learning strategies remain unaltered. The main objective of the present study was to investigate whether the spatial knowledge preserved in the hippocampal animals can be expressed flexibly under conditions different from those of the acquisition period. Rats with neurotoxic lesions to the dorsal hippocampus and sham-operated subjects were trained to reach the goal arm in a four-arm plus-shaped maze using a constant starting arm. During the training a transparent plexiglas barrier divided the maze in two equal halves in such a way that the animals could only travel from the starting arm to the goal arm, not having access to the remaining 50% of the maze. After seven days of training, a transfer test was used in which the starting arms were the two arms from which the animals had not started during the training phase. Results indicated that the lesioned rats made significantly more errors than the control subjects. But the most interesting results revealed that the kind of error made by the lesioned animals was congruent with the turn that they had to make during the acquisition phase in order to access the goal arm (reinforced). These results suggest that when the hippocampus is damaged a preserved highly inflexible egocentric strategy is employed to solve the spatial problem.