Honeybees Use Celestial and/or Terrestrial Compass Cues for Inter‐Patch Navigation

Foraging honeybees (Apis mellifera) are well known to fly straight from the hive, their primary hub, to distal goals as well as between familiar feeding sites. More recently, it was shown that a distal feeding site may be used as a secondary hub. If not fully satiated, the foraging bee may decide to depart the first feeding site in a new compass direction straight to one of many other feeding sites (inter‐patch foraging). Using a recently developed recording method, we discovered that the chosen departure direction at a secondary hub can be guided exclusively by either celestial or terrestrial compass cues. Given our data, we draw two theoretical inferences. First, the bees must be capable of learning and remembering multiple, spatially distinct, navigation vectors between the hive and among multiple feeding sites. Second, this documented and useful representation of multiple navigation vectors between multiple, identified target locations logically implies composite place‐vector mapping, stored in long‐term memory.     

The relationship between the Met allele of the BDNF Val66Met polymorphism and impairments in decision making under ambiguity in patients with obsessive-compulsive disorder

Brain-derived neurotrophic factor (BDNF) gene has an important link to neurotransmitter systems, including serotonin, and seems to play a major role in emotional decision making. Impairment of decision making is an important feature of psychiatric disorders such as obsessive-compulsive disorder (OCD). We explore the link between decision making and the BDNF Val66Met polymorphism, which results in a reduction of BDNF activity, in a sample of Caucasian OCD patients. We used the Iowa Gambling Task (IGT) to measure decision making in 122 OCD patients. All patients were assessed using the Yale-Brown Obsessive-Compulsive Scale, the Beck Depression Inventory, the Beck Anxiety Inventory and the Raven Progressive Matrices. Patients also performed the Continuous Performance Task (CPT-II) and the Trail Making Test (TMT). We grouped Met-allele carriers because these act in a dominant way. Met-allele carries exhibited low performance on both halves of the IGT (first half -F = -2.51, df = 120, P = 0.01; second half -F = -2.32, df = 120, P = 0.02). However, logistic regression analyses showed that the influence of the Met allele seemed to be restricted to the first half of the IGT [first half -β = 0.55, df = 1, P < 0.01, odds ratio (OR) = 5.62; second half -β = 0.32, df = 1, P = 0.15, OR = 2.30]. No differences were observed in tests used to evaluate executive functions associated with the dorsolateral prefrontal cortices (TMT and CPT-II, df = 120, P > 0.05 for both). Met-allele impairment may only be related to decisions made under ambiguous conditions. The null results involving TMT and CPT-II are possibly related to the dysfunction of the orbitofrontal cortices that is associated with OCD.     

Optimal foraging for multiple nutrients in an unpredictable environment

Foraging theory has typically been concerned with the acquisition of a single resource even though organisms from mammals to protozoa are capable of balancing their requirements for multiple resources. Existing theory concerning multiple nutrients from multiple foods does not predict the sequence of food selection. We constructed an optimisation model of the simplest case of two foods containing differing amounts of two nutrients. We begin with the well-supported assumption that reproductive value declines with the distance from target nutrient intake. We show that nutrient space divides into two distinct areas where the animal should exclusively consume one food or the other. The organism thus initially concentrates on one food type until the border between the areas is reached and then moves as closely as possible along the border to approach the target. This strategy is commonly observed in a range of organisms, suggesting that the assumed fitness function is common.     

VIEWS OF THE PROCESS AND CONTENT OF ETHICAL REVIEWS OF HIV VACCINE TRIALS AMONG MEMBERS OF US INSTITUTIONAL REVIEW BOARDS AND SOUTH AFRICAN RESEARCH ETHICS COMMITTEES

Given the ethical controversies concerning HIV vaccine trials (HVTs), we aimed to understand through an exploratory study how members of institutional review boards (IRBs) in the United States (US) and research ethics committees (RECs) in South Africa (SA) view issues concerning the process and content of reviews of these studies. We mailed packets of 20 questionnaires to 12 US IRB chairs and administrators and seven REC chairs to distribute to their members. We received 113 questionnaires (76 from the US and 37 from SA). In both countries, members tended to be white males with advanced academic degrees. Compared to the US, SA members called for ‘major changes’ in HVT protocols more frequently (p = 0.004), and were less likely to think that HVT participants understood risks and benefits (p = 0.033) or informed consent forms (p = 0.000). In both countries, members were divided on several critical issues (e.g. the minimum standard for treatment for HVT participants who became infected during the HVT), but agreed that they needed more training. Of the SA respondents, 40% reported that they were ‘self‐taught’ in ethics. This study, the first we know of to offer quantitative data comparing US vs. non‐US IRBs/RECs, thus suggests key similarities and differences (e.g. compared to SA respondents, US respondents appeared to overestimate participants' understanding of informed consent), along with needs for education. These initial exploratory data in this area have important implications for IRBs, RECs, policy‐makers and scholars concerning future practice, training, policy, and investigations in research ethics, and prevention and treatment of HIV and other diseases in the developing world and elsewhere.     

Optimal Bayesian Design for Patient Selection in a Clinical Study

Summary .  Bayesian experimental design for a clinical trial involves specifying a utility function that models the purpose of the trial, in this case the selection of patients for a diagnostic test. The best sample of patients is selected by maximizing expected utility. This optimization task poses difficulties due to a high-dimensional discrete design space and, also, to an expected utility formula of high complexity. A simulation-based optimal design method is feasible in this case. In addition, two deterministic algorithms that perform a systematic search over the design space are developed to address the computational issues.