Complete recovery of olfactory associative learning by activation of 5-HT4 receptors after dentate granule cell damage in rats

Bilateral intradentate injections of 3.0 μg of colchicine induced a substantial loss of granule cells and damage to the overlying pyramidal cell layer in region CA1 in adult male Long-Evans rats. All rats with such lesions showed a significant associative learning deficit in an olfactory discrimination task, while being unimpaired in the procedural component of this task. Injection of a partial selective 5-HT₄ agonist (SL65.0155; 0.01 mg/kg, i.p., vs. saline) before the third of six training sessions enabled complete recovery of associative learning performance in the lesioned rats. Activation of 5-HT₄ receptors by a selective agonist such as SL65.0155 might therefore provide an opportunity to reduce learning and memory deficits associated with temporal lobe damage, and could be useful for the symptomatic treatment of memory dysfunctions related to pathological aging such as Alzheimer’s disease.     

Inhibition of mGluR1 and IP3Rs impairs long-term memory formation in young chicks

Calcium (Ca²⁺) is involved in a myriad of cellular functions in the brain including synaptic plasticity. However, the role of intracellular Ca²⁺ stores in memory processing remains poorly defined. The current study explored a role for glutamate-dependent intracellular Ca²⁺ release in memory processing via blockade of metabotropic glutamate receptor subtype 1 (mGluR1) and inositol (1,4,5)-trisphosphate receptors (IP₃Rs). Using a single-trial discrimination avoidance task developed for the young chick, administration of the specific and potent mGluR1 antagonist JNJ16259685 (500 nM, immediately post-training, ic), or the IP₃R antagonist Xestospongin C (5 μM, immediately post-training, ic), impaired retention from 90 min post-training. These findings are consistent with mGluR1 activating IP₃Rs to release intracellular Ca²⁺ required for long-term memory formation and have been interpreted within an LTP2 model. The consequences of different patterns of retention loss following ryanodine receptor (RyR) and IP₃R inhibition are discussed.     

Progesterone to ovariectomized mice enhances cognitive performance in the spontaneous alternation, object recognition, but not placement, water maze, and contextual and cued conditioned fear tasks

Research on how steroid hormones mediate mnemonic processes have focused on effects of 17β-estradiol (E₂); yet, progesterone (P₄) co-varies with E₂ across endogenous hormonal milieu, and itself may influence cognitive processes. We investigated the hypothesis that acute P₄ treatment enhances cognitive performance compared to vehicle. Ovariectomized (OVX) c57/BL6J mice were randomly assigned to be subcutaneously injected with oil vehicle or P₄ (10 mg/kg). Mice were trained in the spontaneous alternation, object recognition, object placement, water maze, or fear conditioning tasks, and injected with vehicle or P₄ before training or immediately post-training, and then were tested 1, 4, or 24 h later. The data obtained from these experiments supported our hypothesis. P₄ increased the percentage of spontaneous alterations made in a T-maze more so than did vehicle. P₄, compared to vehicle, increased the percentage of time spent exploring the novel object in the object recognition task, but did not alter performance in the object placement task. P₄, compared to vehicle, decreased latencies to reach the location in the water maze where the platform had been during training in a probe trial, but did not alter performance in the control, cued trial. Compared to vehicle, P₄ treatment increased freezing in contextual and cued fear testing. Thus, acute P₄ treatment to OVX mice can improve cognitive performance across a variety of tasks.     

Intracranial self-stimulation improves memory consolidation in rats with little training

Post-training intracranial electrical self-stimulation can improve learning and memory consolidation in rats. However, the molecular mechanisms involved are not known yet. Since previous paradigms of this kind of facilitation are relatively unsuitable to try a molecular approach, here we develop a single and short model of learning and memory facilitation by post-training self-stimulation that could make easier the research of its neural and molecular basis. Thus, three consecutive experiments were carried out to ascertain whether post-training self-stimulation is able to facilitate memory when learning consists of only a brief (5 trials) two-way active avoidance conditioning session. The results of Experiment 1 showed that it is actually possible, and that 48 h after the acquisition session is a very good time to observe the memory improvement. As a way to probe the retroactive effect of self-stimulation, in Experiment 2 we observed that the same self-stimulation treatment given to the subjects not post-training but 48 h before a single two-way active avoidance session does not improve the acquisition of conditioning. In Experiment 3, we showed that the SS facilitative effect observed 48 h after the acquisition session in Experiment 1 was still maintained one week later. We concluded that post-training intracranial self-stimulation can consistently improve memory consolidation even when little acquisition training is given to the animals in a single training session.     

Decisions among time saving options: when intuition is strong and wrong

When people judge the time that can be saved by increasing the speed of an activity, they are often victims of a time saving bias. That is, they overestimate the time that can be saved by increasing the speed. Judgments of time savings following speed increase when driving follow the Proportion heuristic [Svenson, O. (1970). A functional measurement approach to intuitive estimation as exemplified by estimated time savings. Journal of Experimental Psychology, 86, 204-210]. In a choice between time saving options, this heuristic simplifies to the Ratio rule. The first study tested this rule and found that the Ratio rule predicted incorrect decisions when planning to save traveling time in road traffic. The second study showed that the time saving bias was also present in planning of health care; to specify, in decisions about which one of two clinics to reorganize to save more of the doctors' time for personal contacts with patients. To further test the Ratio rule, Study 3 used a matching procedure in which two decision alternatives were made equal by the participants. The results supported the Ratio rule. Practical implications of the results are discussed including the Planning fallacy. In conclusion, the present set of studies have illustrated a time saving bias and provided evidence explaining why people make systematic errors when judging and deciding about time saved following a speed increase.     

学习惰性研究综述

学习惰性是一种普遍存在的消极心理现象,它对学生和成人的学习造成负面影响.相关的研究国外已有而国内尚无.本研究为帮助学习者克服惰性、更好地学习和发展,在文献检索和典籍查阅的基础上,界定了惰性和学习惰性的概念;探讨了学习惰性的危害、成因及其影响因素;从认知、情绪、行为和易发人群等方面辨析了学习惰性与学习倦怠的异同;建议对学习惰性与学习倦怠采取不同的评估、教育和心理干预措施;最后对如何拓宽与深化学习惰性的研究进行了思考.     

Learning generalization in problem solving by a blue-fronted parrot (<Emphasis Type="Italic">Amazona aestiva</Emphasis>)

Pepperberg (The Alex studies: cognitive and communicative abilities of gray parrots. Harvard University Press, Cambridge;1999) showed that some of the complex cognitive capabilities found in primates are also present in psittacine birds. Through the replication of an experiment performed with cotton-top tamarins (Saguinus oedipus oedipus) by Hauser et al. (Anim Behav 57:565-582; 1999), we examined a blue-fronted parrot's (Amazona aestiva) ability to generalize the solution of a particular problem in new but similar cases. Our results show that, at least when it comes to solving this particular problem, our parrot subject exhibited learning generalization capabilities resembling the tamarins'.     

The application of the first order system transfer function for fitting the 3-arm radial maze learning curve

A mathematical model is described based on the first order system transfer function in the form Y=B3∗exp(−B2∗(X−1))+B4∗(1−exp(−B2∗(X−1))), where X is the learning session number; Y is the quantity of errors, B2 is the learning rate, B3 is resistance to learning and B4 is ability to learn. The model is tested in a light-dark discrimination learning task in a 3-arm radial maze using Wistar and albino rats. The model provided good fits of experimental data under acquisition and reacquisition, and was able to detect strain differences among Wistar and albino rats. The model was compared to Rescorla-Wagner, and was found to be mutually complementary. Comparisons with Tulving’s logarithmic function and Valentine’s hyperbola and the arc cotangent functions are also provided. Our model is valid for fitting averaged group data, if averaging is applied to a subgroup of subjects possessing individual learning curves of an exponential shape.