The Relationship between Event-Based Prospective Memory and Ongoing Task Performance in Chimpanzees (Pan troglodytes)

Prospective memory is remembering to do something at a future time. A growing body of research supports that prospective memory may exist in nonhuman animals, but the methods used to test nonhuman prospective memory differ from those used with humans. The current work tests prospective memory in chimpanzees using a method that closely approximates a typical human paradigm. In these experiments, the prospective memory cue was embedded within an ongoing task. Tokens representing food items could be used in one of two ways: in a matching task with pictures of items (the ongoing task) or to request a food item hidden in a different location at the beginning of the trial. Chimpanzees had to disengage from the ongoing task in order to use the appropriate token to obtain a higher preference food item. In Experiment 1, chimpanzees effectively matched tokens to pictures, when appropriate, and disengaged from the ongoing task when the token matched the hidden item. In Experiment 2, performance did not differ when the target item was either hidden or visible. This suggested no effect of cognitive load on either the prospective memory task or the ongoing task, but performance was near ceiling, which may have contributed to this outcome. In Experiment 3, we created a more challenging version of the task. More errors on the matching task occurred before the prospective memory had been carried out, and this difference seemed to be limited to the hidden condition. This finding parallels results from human studies and suggests that working memory load and prospective memory may have a similar relationship in nonhuman primates

Rhesus Monkeys (Macaca mulatta) Maintain Learning Set Despite Second-order Stimulus-response Spatial Discontiguity

In many discrimination-learning tests, spatial separation between stimuli and response loci disrupts performance in rhesus macaques. However, monkeys are unaffected by such stimulusresponse spatial discontiguity when responses occur through joystick-based computerized movement of a cursor. To examine this discrepancy, five monkeys were tested on a learning-set task that required them to touch computer-graphic levers {which differed in location across experimental phases) with a cursor in order to select an associated test stimulus. The task produced both first-order (joystick and lever) and second-order (lever and stimuli) spatial discontiguity between the stimuli to be discriminated and the discriminative response. Performance was significantly better than chance for all lever locations including locations in which selection of the correct lever required moving the cursor away from the positive stimulus. Thus, rhesus macaques do not attend simply to the region around the cursor in these computerized tests, but rather they attend to relevant stimulus loci even when these are discontiguous with response and reward areas

Biomechanical Performance of Variable and Fixed Angle Locked Volar Plates for the Dorsally Comminuted Distal Radius

Background The ideal treatment strategy for the dorsally comminuted distal radius fracture continues to evolve. Newer plate designs allow for variable axis screw placement while maintaining the advantages of locked technology. The purpose of this study is to compare the biomechanical properties of one variable axis plate with two traditional locked constructs. Methods Simulated fractures were created via a distal 1 cm dorsal wedge osteotomy in radius bone analogs. The analogs were of low stiffness and rigidity to create a worst-case strength condition for the subject radius plates. This fracture-gap model was fixated using one of three different locked volar distal radius plates: a variable axis plate (Stryker VariAx) or fixed axis (DePuy DVR, Smith & Nephew Peri-Loc) designs. The constructs were then tested at physiologic loading levels in axial compression and bending (dorsal and volar) modes. Construct stiffness was assessed by fracture gap motion during the different loading conditions. As a within-study control, intact bone analogs were similarly tested. Results All plated constructs were significantly less stiff than the intact control bone models in all loading modes (p\u3c0.040). Amongst the plated constructs, the VariAx was stiffest axially (p=0.032) and the Peri-Loc was stiffest in bending (p\u3c0.024). Conclusion In this analog bone fracture gap model, the variable axis locking technology was stiffer in axial compression than other plates, though less stiff in bending

Do Social Conditions Affect Capuchin Monkeys’ (Cebus apella) Choices in a Quantity Judgment Task?

Beran et al. (2012) reported that capuchin monkeys closely matched the performance of humans in a quantity judgment test in which information was incomplete but a judgment still had to be made. In each test session, subjects first made quantity judgments between two known options. Then, they made choices where only one option was visible. Both humans and capuchin monkeyswere guided by past outcomes, as they shifted from selecting a known option to selecting an unknown option at the point at which the known option went from being more than the average rate of return to less than the average rate of return from earlier choices in the test session. Here, we expanded this assessment of what guides quantity judgment choice behavior in the face of incomplete information to include manipulations to the unselected quantity.We manipulated the unchosen set in two ways: first, we showed the monkeys what they did not get (the unchosen set), anticipating that “losses” would weigh heavily on subsequent trials in which the same known quantity was presented. Second, we sometimes gave the unchosen set to another monkey, anticipating that this social manipulation might influence the risk-taking responses of the focal monkey when faced with incomplete information. However, neither manipulation caused difficulty for the monkeys who instead continued to use the rational strategy of choosing known sets when they were as large as or larger than the average rate of return in the session, and choosing the unknown (riskier) set when the known set was not sufficiently large. As in past experiments, this was true across a variety of daily ranges of quantities, indicating that monkeys were not using some absolute quantity as a threshold for selecting (or not) the known set, but instead continued to use the daily average rate of return to determine when to choose the known versus the unknown quantity

The Composite Fermion Hierarchy: Condensed States of Composite Fermion Excitations?

A composite Fermion hierarchy theory is constructed in a way related to the original Haldane picture by applying the composite Fermion (CF) transformation to quasiparticles of Jain states. It is shown that the Jain theory coincides with the Haldane hierarchy theory for principal CF fillings. Within the Fermi liquid approach for few electron systems on the sphere a simple interpretation of many-quasiparticle spectra is given and provides an explanation of failure of CF hierarchy picture when applied to the hierarchical $4/11$ state.Comment: 6 pages, Revtex, 4 figures in PostScript, submitted to Phys. Rev. Let

A Markov Chain based method for generating long-range dependence

This paper describes a model for generating time series which exhibit the statistical phenomenon known as long-range dependence (LRD). A Markov Modulated Process based upon an infinite Markov chain is described. The work described is motivated by applications in telecommunications where LRD is a known property of time-series measured on the internet. The process can generate a time series exhibiting LRD with known parameters and is particularly suitable for modelling internet traffic since the time series is in terms of ones and zeros which can be interpreted as data packets and inter-packet gaps. The method is extremely simple computationally and analytically and could prove more tractable than other methods described in the literatureComment: 8 pages, 2 figure

Sequential analysis of biomarkers in cerebrospinal fluid and serum during invasive meningococcal disease

The aim of the present study was to determine the profile of different inflammatory molecules in serum and cerebrospinal fluid (CSF) during invasive meningococcal disease (IMD). Their relationship with IMD severity was also assessed. A cohort of 12 patients with IMD was investigated. Paired serum and CSF samples were obtained at the time of diagnostic and follow-up lumbar puncture and were examined using Luminex® analysis. IMD severity correlated with serum interleukin-6 (IL-6) and interleukin-1 receptor antagonist (IL-1ra) on admission. Furthermore, the CSF levels of IL-1β, IL-1ra, IL-6, IL-8, macrophage inflammatory protein-1β (MIP-1β), and monocyte chemoattractant protein-1 (MCP-1) were significantly higher than their respective serum levels. The strongest correlations were found between serum concentrations of IL-1β and IL-1ra, IL-6, IL-8, and MIP-1β, whereas the strongest correlations in CSF were found between endotoxin and IL-8, IL-17, MIP-1β, and MCP-1. As was expected, the concentrations of inflammatory molecules in both serum and CSF significantly decreased after antibiotic treatment. With regard to kinetics, a severe course of IMD correlated positively with rapid declines of CSF IL-6 and cortisol levels. Sequential multiple analyses revealed patterns of inflammatory responses that were associated with the severity of IMD, as well as with the compartmentalization and kinetics of the immune reaction

Human and Monkey Responses in a Symmetric Game of Conflict with Asymmetric Equilibria

To better understand the evolutionary history of human decision-making, we compare human behavior to that of two monkey species in a symmetric game of conflict with two asymmetric equilibria. While all of these species routinely make decisions in the context of social cooperation and competition, they have different socio-ecologies, which leads to different predictions about how they will respond. Our prediction was that anti-matching would be more difficult than matching in a symmetric coordination with simultaneous moves. To our surprise, not only do rhesus macaques frequently play one asymmetric Nash equilibrium, but so do capuchin monkeys, whose play in the coordination game was literally not distinguishable from randomness (in simultaneous play). Humans are the only species to play both asymmetric equilibria in a repeated game