The Biology and Psychology of Crowding in Man and Animals

Author Institution: Professor of Pathobiology, The Johns Hopkins University, Baltimore, Maryland 21205Crowding is an ecologic and psychologic aspect of population density which produces a significant impact upon the behavior and physiology both of individuals and of social groups. In animal populations, an optimal level of crowding is often necessary for favorable social interactions, reproduction, and normal group organization. Beyond optimal levels, however, crowding may become a detrimental influence on the well-being of individuals within the population. Crowded animal populations often show a breakdown of normal social behavior, with increased aggression and violence, aberrant sexual activity, improper parental care, and abnormal states of activity, aggregation, or social withdrawal. A variety of stressrelated diseases and mortality patterns may ensue. The human populations of the world are rapidly becoming more crowded through excessive rates of population growth, urbanization, and increased social and communicative contact. Many urban areas throughout the world are showing classic symptoms of crowded animal populations. We cannot, however, attribute all such symptoms to crowding per se, nor can we adequately distinguish all of the multiple interactions of social, economic, political, and biological factors in producing the "inner-city syndrome." In viewing the complex problems of urban ecology and social behavior, it is important to maintain ecologic perspective and to work toward understanding the interactional relationships between man's physical, social, and biologic environments

Neural computations of threat in the aftermath of combat trauma

By combining computational, morphological, and functional analyses, this study relates latent markers of associative threat learning to overt post-traumatic stress disorder (PTSD) symptoms in combat veterans. Using reversal learning, we found that symptomatic veterans showed greater physiological adjustment to cues that did not predict what they had expected, indicating greater sensitivity to prediction errors for negative outcomes. This exaggerated weighting of prediction errors shapes the dynamic learning rate (associability) and value of threat predictive cues. The degree to which the striatum tracked the associability partially mediated the positive correlation between prediction-error weights and PTSD symptoms, suggesting that both increased prediction-error weights and decreased striatal tracking of associability independently contribute to PTSD symptoms. Furthermore, decreased neural tracking of value in the amygdala, in addition to smaller amygdala volume, independently corresponded to higher PTSD symptom severity. These results provide evidence for distinct neurocomputational contributions to PTSD symptoms

Lions and Prions and Deer Demise

Background: Contagious prion diseases – scrapie of sheep and chronic wasting disease of several species in the deer family – give rise to epidemics that seem capable of compromising host population viability. Despite this prospect, the ecological consequences of prion disease epidemics in natural populations have received little consideration. Methodology/Principal Findings: Using a cohort study design, we found that prion infection dramatically lowered survival of free-ranging adult (.2-year-old) mule deer (Odocoileus hemionus): estimated average life expectancy was 5.2 additional years for uninfected deer but only 1.6 additional years for infected deer. Prion infection also increased nearly fourfold the rate of mountain lions (Puma concolor) preying on deer, suggesting that epidemics may alter predator–prey dynamics by facilitating hunting success. Despite selective predation, about one fourth of the adult deer we sampled were infected. High prevalence and low survival of infected deer provided a plausible explanation for the marked decline in this deer population since the 1980s. Conclusion: Remarkably high infection rates sustained in the face of intense predation show that even seemingly complete ecosystems may offer little resistance to the spread and persistence of contagious prion diseases. Moreover, the depression of infected populations may lead to local imbalances in food webs and nutrient cycling in ecosystems in which deer ar

Calibration of the CMS hadron calorimeters using proton-proton collision data at root s=13 TeV

Methods are presented for calibrating the hadron calorimeter system of theCMSetector at the LHC. The hadron calorimeters of the CMS experiment are sampling calorimeters of brass and scintillator, and are in the form of one central detector and two endcaps. These calorimeters cover pseudorapidities vertical bar eta vertical bar ee data. The energy scale of the outer calorimeters has been determined with test beam data and is confirmed through data with high transverse momentum jets. In this paper, we present the details of the calibration methods and accuracy.Peer reviewe