Dissociation of Hippocampal and Striatal Contributions to Spatial Navigation in the Water Maze

Two experiments were conducted to compare the effects of fornix/fimbria and caudate-putamen lesions in Long–Evans hooded rats (Rattus norvegicus) trained on two water maze tasks that differed in the type of spatial localization required for optimum solution. In Experiment 1, the lesioned rats and surgical controls were trained on the standard place task in the water maze (Morris, 1981) and given two postacquisition tests (a platform removal probe and platform relocation test). In Experiment 2, rats with similar lesions and control rats were trained on a modified cue navigation task. Fornix/fimbria lesions impaired a late stage of place task acquisition but did not impair acquisition of the cue task. Caudate-putamen lesions resulted in a severe place acquisition impairment and a transient cue acquisition impairment, both of which were characterized by an initial tendency to swim near the wall of the pool. Post-hoc analyses of the direction and angles of departure from the start points suggested that rats with fornix/fimbria lesions used non-allocentric spatial strategies to solve the place task. These rats also demonstrated a significantly weakened spatial bias for the former training quadrant on the platform removal probe and reduced flexibility in navigating to a novel platform location on the platform relocation test. In contrast, rats with caudate-putamen lesions showed a significant spatial bias for the former training quadrant but failed to cross the exact location within the quadrant where the platform was formerly positioned. The results suggest that the hippocampus mediates the allocentric spatial component of the water maze place task while the dorsomedial striatum may play an important role in the acquisition of the procedural aspects of both place and cue versions of the task.     

Quality of care and cost containment in the U.S. and U.K.

Many activities of doctors in the acute hospital sector do not improve patient outcome because they are inappropriate. Curtailing interventions that are unnecessary (because the patient is not bad enough) or are unsuccessful (because the condition is too advanced) could both save resources and improve care. Rational rationing depends on knowledge about the expected benefits of various technologies when used in different clinical circumstances.     

Aversive potency of urine from dominant and subordinate male laboratory mice (Mus musculus): Resolution of a conflict

The present study assessed the aversive potency of urine collected from male albino mice that had been clearly identified as dominants/winners or subordinates/losers of paired aggression tests and then housed either individually or in a quasi-paired situation in which only a wire-mesh divider separated the two mice. This divider permitted constant visual, olfactory, auditory, and some tactile contact. The responses of individually tested, group-housed males were recorded when half of the substrate in a test box was treated with either water or one of the four urine types; the other half remained untreated. Significant preferences for the untreated half were found when the urine of winners or losers housed in individual metabolism cages or that of pair-housed dominants was used as the test stimulus. On the other hand, neither water nor the urine of cohabiting subordinate males was avoided. The present findings confirmed our earlier reports that the urine of dominant male mice was aversive, whereas that of their cohabiting subordinate partners was not. They also identified Sawyer's [1978] procedure of housing winners and losers in individual cages, with the consequent interruption of social contact as the likely reason for his failure to replicate our reports that subordinate male urine lacked aversive properties. The territorial implications of the aversive factor and other urinary signals are discussed.     

Are Propositions Essentially Representational?

Jeffrey King argues that nothing has truth conditions except by being taken to be true or false by rational agents. But – for good reason – King claims that propositions possess truth conditions essentially and intrinsically. I will argue that King cannot have both: if the truth conditions of a proposition depend on the reactions of rational agents, then the possession of truth conditions can't follow from the intrinsic nature or existence of the proposition. This leaves two options. Either, nothing can do the job that motivates positing propositions. Or, there is no need to explain what bestows a truth condition on a proposition.     

Marijuana use and risky sexual behavior among high-risk adolescents: Trajectories, risk factors, and event-level relationships

Adolescents involved with the juvenile justice system have a high incidence of risky sexual behaviors resulting in unintended pregnancy and sexually transmitted infections. Substance use may be particularly important as a risk factor for unsafe sexual behavior for this group, and recent evidence suggests a possible association between marijuana use and risky sexual behavior. Adolescents (n = 728; 33% female) on probation were followed for 2 years, at intervals of 6 months, to explore the association of marijuana use and condom use longitudinally and at a specific intercourse occasion. Latent growth curve modeling indicated that greater marijuana use at baseline was associated with a steeper decline in condom use over the 2-year period of the study. In-depth analysis of the most recent intercourse occasion suggested that condom use was less likely if marijuana was being used by the participant or his/her partner and that this association was more pronounced if intercourse occurred with someone the participant had just met. Implications for the prevention of risky sexual behavior in this population are discussed. (PsycINFO Database Record (c) 2012 APA, all rights reserved).