Selective lesions of the dentate gyrus produce disruptions in place learning for adjacent spatial locations

The hippocampus (HPP) plays a known role in learning novel spatial information. More specifically, the dentate gyrus (DG) hippocampal subregion is thought to support pattern separation, a mechanism for encoding and separating spatially similar events into distinct representations. Several studies have shown that lesions of the dorsal DG (dDG) in rodents result in inefficient spatial pattern separation for working memory; however, it is unclear whether selective dDG lesions disrupt spatial pattern separation for reference memory. Therefore, the current study investigated the role of the dDG in pattern separation using a spatial reference memory paradigm to determine whether the dDG is necessary for acquiring spatial discriminations for adjacent locations. Male Long-Evans rats were randomly assigned to receive bilateral intracranial infusions of colchicine or saline (control) into the dDG. Following recovery from surgery, each rat was pseudo-randomly assigned to an adjacent arm or separate arm condition and subsequently tested on a place-learning task using an eight-arm radial maze. Rats were trained to discriminate between a rewarded arm and a nonrewarded arm that were either adjacent to one another or separated by a distance of two arm positions. Each rat received 10 trials per day and was tested until the animal reached a criterion of nine correct choices out of 10 consecutive trials across 2 consecutive days of testing. Both groups acquired spatial discriminations for the separate condition at similar rates. However, in the adjacent condition, dDG lesioned animals required significantly more trials to reach the learning criterion than controls. The results suggest that dDG lesions decrease efficiency in pattern separation resulting in impairments in the adjacent condition involving greater overlap among the distal cues. Conversely, in the separate condition, there was less overlap among distal cues during encoding and less need for pattern separation. These findings provide further support for a critical role for the dDG in spatial pattern separation by demonstrating the importance of a processing mechanism that is capable of reducing interference among overlapping spatial inputs across a variety of memory demands.     

Cadre et confidentialité de l’entretien clinique en psychologie scolaire : quelles représentations chez les professionnels ? Une recherche qualitative exploratoire

Despite the fact that the issue of the framework reveals many ethico-clinical considerations in the literature, confidentiality is rarely mentioned. How do professionals working in schools (psychologists, speech therapists, psychomotricians) see the rules of confidentiality? When faced with a fictitious dilemma, do they apply rules that are related only to the clinical framework? This qualitative study explores the representations of 20 professionals recorded during the discussions of two focus groups. Discourse analysis of thematic markers reveals that, in terms of frequency, two thirds of the rules invoked by the subjects are ethico-clinical rules, while the rest are legal or institutional, or appeal to another indeterminate reference.     

The effects of varied retrieval cues on reminiscence in eyewitness memory

Eyewitnesses sometimes recall things at later interviews that they did not recall at previous interviews (reminiscence). When these cases are argued in the courtroom, attorneys may claim (and judges may warn jurors) that eyewitnesses who provide reminiscences are necessarily inaccurate witnesses. Consequently, their testimony may be prematurely discredited or dismissed. We examined here the role of varying the retrieval cues across interviews to account for reminiscence. Participants watched a videotaped mock crime and were tested for recall on two occasions using the same or different cues. Results supported the hypothesis that varying retrieval cues increases the amount of reminiscence. Furthermore, nearly all participants exhibited some reminiscence. Finally, reminiscence was not significantly correlated with overall accuracy of testimony. These findings suggest that many of the assumptions underlying legal tactics and judges' instructions regarding reminiscent inconsistencies are erroneous. Copyright © 2006 John Wiley & Sons, Ltd.