A study on the role of the dorsal striatum and the nucleus accumbens in allocentric and egocentric spatial memory consolidation

There is now accumulating evidence that the striatal complex in its two major components, the dorsal striatum and the nucleus accumbens, contributes to spatial memory. However, the possibility that different striatal subregions might modulate specific aspects of spatial navigation has not been completely elucidated. Therefore, in this study, two different learning procedures were used to determine whether the two striatal components could be distinguished on the basis of their involvement in spatial learning using different frames of reference: allocentric and egocentric. The task used involved the detection of a spatial change in the configuration of four objects placed in an arena, after the mice had had the opportunity to experience the objects in a constant position for three previous sessions. In the first part of the study we investigated whether changes in the place where the animals were introduced into the arena during habituation and testing could induce a preferential use of an egocentric or an allocentric frame of reference. In the second part of the study we performed focal injections of the N-methyl-d-aspartate (NMDA) receptors' antagonist, AP-5, within the two subregions immediately after training. The results indicate that using the two behavioral procedures, the animals rely on an egocentric and an allocentric spatial frame of reference. Furthermore, they demonstrate that AP-5 (37.5, 75, and 150 ng/side) injections into the dorsal striatum selectively impaired consolidation of spatial information in the egocentric but not in the allocentric procedure. Intra-accumbens AP-5 administration, instead, impaired animals trained using both procedures.     

Differential involvement of NMDA and AMPA receptors within the nucleus accumbens in consolidation of information necessary for place navigation and guidance strategy of mice

Recent evidence now points to a role of glutamate transmission within the nucleus accumbens (Nacc) in spatial learning and memory. Unfortunately, the role of the distinct classes of glutamate receptors within this structure in mediating the different steps of the memorization process is not clear. The aim of this study therefore was to further investigate this issue, trying to assess the involvement of the two classes of glutamate receptors within the Nacc in consolidation of spatial information using an associative spatial task, the water maze. For this purpose, focal injections of the NMDA antagonist, AP-5, and of the AMPA antagonist, DNQX, have been performed immediately after the training phase, and mice have been tested for retention 24 h later. Two different versions of the water-maze task have been used: In the place version, animals could learn the position of the platform using visual distal cues, and in the cue version, the location of the platform was indicated by a single proximal cue. The results demonstrated that posttraining NMDA receptor blockade affects mice response in the place but not in the cue water-maze task. On the contrary, AMPA receptor blockade induced no effect in either version of the task. These data confirm a functional dissociation between glutamate receptors located in the Nacc in modulating spatial memory consolidation and indicate that they are specifically involved in consolidation of information necessary to acquire a place but not to a guidance strategy.     

Moral Responsibility and History Revisited

Compatibilists about determinism and moral responsibility disagree with one another about the bearing of agents’ histories on whether or not they are morally responsible for some of their actions. Some stories about manipulated agents prompt such disagreements. In this article, I call attention to some of the main features of my own “history-sensitive” compatibilist proposal about moral responsibility, and I argue that arguments advanced by Michael McKenna and Manuel Vargas leave that proposal unscathed.     

Developing an Online Early Detection System for School Attendance Problems: Results From a Research-Community Partnership

School refusal and other school attendance problems are vexing problems for school-aged youth, families, school personnel, and clinicians. However, few resources exist to detect problematic attendance. The current report describes three steps of a research-community partnership to develop an early identification program to detect youth at risk for problematic attendance. First, a survey was conducted to estimate the scope and cost of school refusal across grades K–12. School administrators estimated relatively few youth exhibiting significant school refusal (missing 5 or more days per year) but estimated the costs associated with services for these youth to be very high (mean cost of in-district programs: $94,052; mean cost of out-of-district placements: $496,657). Second, elementary school counselors were tasked with tracking absenteeism among at-risk youth using an online attendance tracking prototype. Counselors identified a high number of youth who showed elevated absences, lates, or early departures (17.2% of enrolled students), and counselor ratings were significantly related to whether the student (a) had received an individualized education plan or 504 plan, (b) had a sibling with similar attendance problems, (c) was older, or (d) had divorced or separated parents. In a final step, counselor feedback was sought and revisions were incorporated in the attendance tracker. Findings reinforce the prevalence and cost of school attendance problems, provide guidance for using technology to monitor attendance and related indices (tardies, early departures), and direct attention to youth factors that may be useful in identifying youth at risk for poor attendance.