Probabilistic Inference in General Graphical Models through Sampling in Stochastic Networks of Spiking Neurons

An important open problem of computational neuroscience is the generic organization of computations in networks of neurons in the brain. We show here through rigorous theoretical analysis that inherent stochastic features of spiking neurons, in combination with simple nonlinear computational operations in specific network motifs and dendritic arbors, enable networks of spiking neurons to carry out probabilistic inference through sampling in general graphical models. In particular, it enables them to carry out probabilistic inference in Bayesian networks with converging arrows (“explaining away”) and with undirected loops, that occur in many real-world tasks. Ubiquitous stochastic features of networks of spiking neurons, such as trial-to-trial variability and spontaneous activity, are necessary ingredients of the underlying computational organization. We demonstrate through computer simulations that this approach can be scaled up to neural emulations of probabilistic inference in fairly large graphical models, yielding some of the most complex computations that have been carried out so far in networks of spiking neurons

A Continental-Wide Perspective: The Genepool of Nuclear Encoded Ribosomal DNA and Single-Copy Gene Sequences in North American Boechera (Brassicaceae)

74 of the currently accepted 111 taxa of the North American genus Boechera (Brassicaceae) were subject to pyhlogenetic reconstruction and network analysis. The dataset comprised 911 accessions for which ITS sequences were analyzed. Phylogenetic analyses yielded largely unresolved trees. Together with the network analysis confirming this result this can be interpreted as an indication for multiple, independent, and rapid diversification events. Network analyses were superimposed with datasets describing i) geographical distribution, ii) taxonomy, iii) reproductive mode, and iv) distribution history based on phylogeographic evidence. Our results provide first direct evidence for enormous reticulate evolution in the entire genus and give further insights into the evolutionary history of this complex genus on a continental scale. In addition two novel single-copy gene markers, orthologues of the Arabidopsis thaliana genes At2g25920 and At3g18900, were analyzed for subsets of taxa and confirmed the findings obtained through the ITS data

Comparison of Two Clinical Protocols for Total Intravenous Anesthesia (TIVA) for Breast Surgery Using Propofol Combined With Either Sufentanil or Alfentanil

BACKGROUND: Sufentanil and alfentanil have pharmacokinetic and dynamic properties which make them favourable substances for total intravenous anesthesia (TIVA) in combination with propofol. OBJECTIVES: We planned to compare two clinical protocols for TIVA with propofol, and either sufentanil or alfentanil in regards to postoperative pain, hemodynamic stability during the case and time for emergence from anesthesia. PATINETS AND METHODS: Treaty eight patients scheduled for general anesthesia for breast surgery were included in this Double-blind, randomized, controlled trial. All patients received a standardized TIVA with propofol and either 0.2 µg kg(-1) sufentanil or 20 µg kg(-1) alfentanil for induction and 0.3 µg kg(-1) h(-1) sufentanil or 30 µg kg(-1) h(-1) alfentanil for maintenance with additional propofol boluses as needed. During anesthesia, heart rate, non-invasive blood-pressure, peripheral oxygen saturation and depth of anesthesia, were recorded. In the post anesthesia care unit, pain scores, nausea and vomiting as well as medications were recorded. RESULTS: Patients in the sufentanil group required less often additional opioid and propofol boluses to maintain adequate anesthesia. We did not observe a significant difference in time to extubation. Postoperatively, patients in the sufentanil group had less pain (P = 0.03) and required less i.v. opioids (0.4 vs. 1.9 mg piritramid, P = 0.04). CONCLUSIONS: Both protocols provide excellent anesthesia, but patients receiving sufentnail had more stable anesthesia and less postoperative pain