How structure informs and transforms chemogenetics

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Ethics, evidence, and public policy

The growth of evidence-based medicine (EBM) raises a number of ethical issues that have too often been overlooked. These include issues that arise when clinicians make judgments under uncertainty, new challenges for the clinician-patient relationship, new duties for institutional review boards, issues in physician autonomy and reimbursement, and challenges for disclosure and informed consent. Ethics and EBM must be addressed by policy makers and integrated into medical education.     

Interaction rate informs harvester ant task decisions

Social insect colonies operate without central control, andcolony organization results from the ways that individuals respondto local information. We investigated how temporal information,in particular the rate of interaction among workers, stimulatesforaging activity in the red harvester ant (Pogonomyrmex barbatus).Patrollers scout the foraging area each morning. Previous workshowed that the patrollers' safe return to the nest stimulatesthe foragers to leave the nest; if the patrollers do not return,the foragers do not emerge. Here, we tested whether contactwith returning patrollers must occur at a particular rate tostimulate foraging. We varied the rates at which we introducedpatroller mimics, glass beads coated with an extract of thecuticular hydrocarbons of patrollers. A return rate of 1 patrollermimic every 10 s stimulated the highest level of foraging activity.We found that the onset of foraging depends on the rate of patrollerreturn. Adding beads coated with patroller hydrocarbons at arate of 1 per 10 s caused otherwise undisturbed colonies toforage 17.9 ± 19.7 (standard deviation) min faster thancolonies that received blank control beads. These results showthat rate is a crucial source of information in the networkof interactions among workers.     

Bifurcation analysis informs Bayesian inference in the Hes1 feedback loop

Background  

Ordinary differential equations (ODEs) are an important tool for describing the dynamics of biological systems. However, for ODE models to be useful, their parameters must first be calibrated. Parameter estimation, that is, finding parameter values given experimental data, is an inference problem that can be treated systematically through a Bayesian framework.     

How humans evolved large brains: Comparative evidence

The human brain is about three times as large as that of our closest living relatives, the great apes. Overall brain size is a good predictor of cognitive performance in a variety of tests in primates. 1 , 2 Therefore, hypotheses explaining the evolution of this remarkable difference have attracted much interest. In this review, we give an overview of the current evidence from comparative studies testing these hypotheses. If cognitive benefits are diverse and ubiquitous, it is possible that most of the variation in relative brain size among extant primates is explained by variation in the ability to avoid the fitness costs of increased brain size (allocation trade‐offs and increased minimum energy needs). This is indeed what we find, suggesting that an energetic perspective helps to complement approaches to explain variation in brain size that postulate cognitive benefits. The expensive brain framework also provides a coherent scenario for how these factors may have shaped early hominin brain expansion.