A comparison of methods to determine neuronal phase-response curves

The phase-response curve (PRC) is an important tool to determine the excitability type of single neurons which reveals consequences for their synchronizing properties. We review five methods to compute the PRC from both model data and experimental data and compare the numerically obtained results from each method. The main difference between the methods lies in the reliability which is influenced by the fluctuations in the spiking data and the number of spikes available for analysis. We discuss the significance of our results and provide guidelines to choose the best method based on the available data.Comment: PDFLatex, 16 pages, 7 figures

Nesting Giant Canada Geese in Western South Dakota

Giant Canada geese (Branta Canadensis maxima) began nesting on 27 March 1976 and 2 April 1977. Peak hatch occurred from 15 to 21 May 1976 and 22 to 28 May 1977 and the nesting season lasted 69 days in 1976 and 83 days in 1977. Average clutch size was 4.8 eggs per nest in 1976 and 5.0 in 1977. Thirty-three percent of all eggs observed in 1976 and 23% in 1977 failed to hatch. Infertility and desertion were the main reasons that eggs did not hatch. Seventy percent of the territorial pairs in 1976 and 41% in 1977 nested. Nesting success was 76% in 1976 and 79% in 1977. Mean brood size was 4.6 in 1976 and 4.7 in 1977. The estimated number of geese in the study area in 1977 was 1196 of which 573 were territorial pairs (0.5 geese per section). Approximately 3.7 goslings per breeding pair in 1976 and 3.5 goslings in 1977 survived through the flight stage. Thirty variable were analyzed using a discriminant function analysis to evaluate goose nesting habitat on stockponds. Size, headwater development, presence of an island, permanence of the pond and disturbance by livestock accounted for 52% of the variation between ponds used and ponds not used by geese. Stockponds were assigned to 1 of 4 habitat classes with Class 4 representing optimal goose nesting habitat. Size, headwater development, percent basin water, density of surrounding vegetation, distance to nearest farmstead, and southward drainage were the 6 variables which best separated the 4 classes of ponds. When “class” and the other 30 variables were entered into the analysis the presence of absence of geese on stockponds was predicted by the computer with 92% and 93% accuracy, respectively. A total of 2674 stockponds was estimated for the study area of which 1390 (52%) ponds were considered to have potential as goose nesting habitat

Methods of regularization for computing orbits in celestial mechanics

Numerical and analytical methods for orbit computation in celestial mechanics during and beyond collision by introduction of regularized coordinate

Building legitimacy by criticising the pharmaceutical industry: a qualitative study among prescribers and local opinion leaders.

PRINCIPLES: The literature has described opinion leaders not only as marketing tools of the pharmaceutical industry, but also as educators promoting good clinical practice. This qualitative study addresses the distinction between the opinion-leader-as-marketing-tool and the opinion-leader-as-educator, as it is revealed in the discourses of physicians and experts, focusing on the prescription of antidepressants. We explore the relational dynamic between physicians, opinion leaders and the pharmaceutical industry in an area of French-speaking Switzerland. METHODS: Qualitative content analysis of 24 semistructured interviews with physicians and local experts in psychopharmacology, complemented by direct observation of educational events led by the experts, which were all sponsored by various pharmaceutical companies. RESULTS: Both physicians and experts were critical of the pharmaceutical industry and its use of opinion leaders. Local experts, in contrast, were perceived by the physicians as critical of the industry and, therefore, as a legitimate source of information. Local experts did not consider themselves opinion leaders and argued that they remained intellectually independent from the industry. Field observations confirmed that local experts criticised the industry at continuing medical education events. CONCLUSIONS: Local experts were vocal critics of the industry, which nevertheless sponsor their continuing education. This critical attitude enhanced their credibility in the eyes of the prescribing physicians. We discuss how the experts, despite their critical attitude, might still be beneficial to the industry's interests

An Inverse Approach for Elucidating Dendritic Function

We outline an inverse approach for investigating dendritic function–structure relationships by optimizing dendritic trees for a priori chosen computational functions. The inverse approach can be applied in two different ways. First, we can use it as a “hypothesis generator” in which we optimize dendrites for a function of general interest. The optimization yields an artificial dendrite that is subsequently compared to real neurons. This comparison potentially allows us to propose hypotheses about the function of real neurons. In this way, we investigated dendrites that optimally perform input-order detection. Second, we can use it as a “function confirmation” by optimizing dendrites for functions hypothesized to be performed by classes of neurons. If the optimized, artificial, dendrites resemble the dendrites of real neurons the artificial dendrites corroborate the hypothesized function of the real neuron. Moreover, properties of the artificial dendrites can lead to predictions about yet unmeasured properties. In this way, we investigated wide-field motion integration performed by the VS cells of the fly visual system. In outlining the inverse approach and two applications, we also elaborate on the nature of dendritic function. We furthermore discuss the role of optimality in assigning functions to dendrites and point out interesting future directions

Calling situated: a survey among medical students supplemented by a qualitative study and a comparison with a surveyed sample of physicians.

Calling within the medical context receives growing academic attention and empirical research has started to demonstrate its beneficial effects. The purpose of this study is to investigate what motivates students to enter medical school and what role calling may play (i), to evaluate if calling influences the way in which they experience their studies (ii), and to compare medical students' experience of calling with those of physicians. A questionnaire survey was distributed among medical students (N = 1048; response rate above 60%) of the University of Lausanne in Switzerland. It was supplemented by a group discussion between bachelor medical students (N = 8) and senior physicians (N = 4), focusing on different facets of calling. An existing data set of a survey among physicians, addressing calling with the same questionnaire, was used to compare students' and physicians' attitudes towards calling. Survey data were analyzed with the habitual statistical procedures for categorical and continuous variables. The group discussion was analyzed with thematic analysis. The survey showed that experiencing calling is a motivational factor for study choice and influences positively choice consistency. Students experiencing calling differed from those who did not: they attributed different definitions to calling, indicated more often prosocial motivational factors for entering medical school and perceived the learning context as less burdensome. The analysis of the group discussion revealed that the concept of calling has a fluid definition. It was conceived as having the characteristics of a double-edged sword and as originating from within or outside or from a dialectic interplay between the inner and outer world. Finally, calling is experienced less often by physicians than by medical students, with a decreasing prevalence as the immersion in the clinical years of the study of medicine progresses. Calling plays an important role in study choice and consistency of medical students. Given its relevance for medical students and its ramifications with the learning context, calling should become a topic of the reflexive parts of the medical curriculum. We critically discuss the role played by calling for medical students and provide some perspectives on how calling could be integrated in the reflection and teaching on physicianhood