Cognitive performances and locomotor activity following dentate granule cell damage in rats: role of lesion extent and type of memory tested

Intradentate injection of colchicine is one of the techniques used to destroy granule cells. This study compared the behavioral effects of various amounts of colchicine (1.0, 3.0, and 6.0 microg; Col 1, Col 3, and Col 6, respectively) injected into the dentate gyrus of adult Long-Evans male rats. Starting 10 days after lesion surgery, behavioral testing assessed home-cage and open-field locomotion, alternation in a T-maze, water-maze, and radial-maze learning according to protocols placing emphasis on reference, and working memory. All of these tasks are sensitive to hippocampal disruption. Histological verifications showed that the extent of the lesions depends on the dose of colchicine (index of dentate gyrus shrinkage: -33% in Col 1, -54% in Col 3, and -67% in Col 6 rats). Colchicine dose-dependently increased nocturnal home cage activity (an effect found 10 days but not 5 months after surgery), but had no significant effect on open-field locomotion or T-maze alternation. A dose-dependent reference memory impairment was found during the acquisition of spatial navigation in the water maze; Col 3 and Col 6 rats were more impaired than Col 1 rats. During the probe trial (platform removed), control rats spent a longer distance swimming over the platform area than all rats with colchicine lesions. In the working memory version of the test, all rats with colchicine lesions showed significant deficits. The deficits were larger in Col 3 and Col 6 rats compared to Col 1 rats. The lesions had no effect on swimming speed. In the radial-maze test, there was also a dose-dependent working memory impairment. However, reference memory was disrupted in a manner that did not differ among the three groups of lesioned rats. Our data are in line with the view that the dentate gyrus plays an important role in the acquisition of new information and is an integral neural substrate for spatial reference and spatial working memory. They also suggest that damage to granule cells might have more pronounced effects on reference than on working memory in the radial maze. Finally, they demonstrate that part of the variability in the conclusions from previous experiments concerning the role of granule cells in cognitive processes, particularly in spatial learning and memory, may be due to the type of tests used and/or the extent of the damage produced.     

Victimization and delinquency among Canadian youth.

This study examined the extent of victimization and delinquency in the past year among 962 junior and senior high school students in a large Canadian city. The incidence of having a weapon at school was also investigated. Further, relationships between victimization, delinquency, and weapon possession were explored. The prevalence of self-reported victimization was found to be high, both while the youths were at school and while not at school. Except for victimization of a sexual nature, males reported higher rates of victimization, in and out of school, than did females. In general, younger students reported higher rates of victimization at school than did older students. In addition, over half of the students reported engaging in some form of delinquent behavior within the past year. Males, as compared with females, were more likely to report engaging in a variety of delinquent behaviors. Interestingly, students in grade 9 were more likely to report delinquent behaviors than were students in other grades. Students who reported moderate/high levels of delinquency were more likely to report moderate/high levels of victimization, and students who reported no delinquency were more likely to report no victimization.     

Elaboration et validation de tests de jugement situationnel comme outil de sélection professionnelle : guide méthodologique

Current views in personnel selection recognize the necessity for situational judgements tests (SJT) which are closed to the real work context of companies. The SJTs have also become a popular selection tool across Europe. SJTs are attractive because they show good validity, positive applicants reactions and can be cost effective to test large group of applicants at once. The aim of this paper is to describe a structured methodology for the elaboration of such test. Each stage is illustrated by examples and psychometrics validation issues are discussed.     

Short-term memory performances during sustained wakefulness in patients with obstructive sleep apnea-hypopnea syndrome

Both working and immediate memories were assessed every 4h by specific short-term memory tasks over sustained wakefulness in 12 patients with obstructive sleep apnea and hypopnea syndrome (OSAHS) and 10 healthy controls. Results indicated that OSAHS patients exhibited lower working memory performances than controls on both backward digit span and complex Sternberg tasks. Speed and accuracy on Sternberg tasks were affected by memory load in both groups. However, immediate memory was not impaired in OSAHS patients. Diurnal and nocturnal SaO(2) were correlated with speed and accuracy high-speed memory scanning performance on Sternberg tasks in patients. These results suggest specific working memory deficits associated with OSAHS over sustained wakefulness with a possible deficiency in the central executive responsible for the higher information processing, in addition to a potentially insufficient storage capacity. Among OSAHS patients, working memory ability involved in high-speed memory scanning may be impaired by chronic hypoxemia.     

Visual discrimination by heifers (Bos taurus) of their own species

Species discrimination has been described in several taxa but rarely in domestic animals. In contrast to wild species, domestic species present a great phenotypic variety. This study investigated whether 10 Prim'Holstein heifers (Bos taurus) could discriminate images of cows from images of other domestic animals. The experiment was based on simultaneous discrimination. Responses were obtained through instrumental conditioning using a food reward. In Experiment 1, the reward was associated with a cow face and, in the reversal learning task, with faces of other domestic species. The results showed that in both tasks, cows were able to reach the criterion in few sessions. Therefore, despite great phenotypic variety (a cognitive challenge) cows were able to visually discriminate their own species from other domestic species.     

The inhibitory avoidance test optimized for discovery of cognitive enhancers

In the present article, we describe a new protocol for the inhibitory avoidance test, with a dual purpose: (1) to provide a leß variable and more reliable aßeßment of the efficacy of potential cognitive enhancers in antagonizing scopolamine-induced long-term-memory deficits, and (2) to secure a high throughput for pharmacological screening of cognitive enhancers. The new protocol consists of two acquisition trials that are followed 24 h later by a single retention trial. In the present study, this protocol clearly dißociated the frequency distributions of retention latencies between scopolamine- and vehicle-treated groups and allowed validation by means of two acetylcholinesterase inhibitors—tacrine and donepezil—that proved to be active in counteracting the scopolamine-induced memory deficit. This protocol also produced stability of the behavioral response to pharmacological agents over a 3-year period. A statistical power analysis indicated that, depending on the efficacy of the drug/dose, a sample size of 5–12 mice was required in order to show a reversal of the scopolamineinduced memory deficit. The double-trial acquisition protocol is suitable for testing cognitive enhancers, while also providing a clearly enhanced throughput.