Attention, predictive learning, and the inverse base-rate effect: Evidence from event-related potentials

We report the first electrophysiological investigation of the inverse base-rate effect (IBRE), a robust non-rational bias in predictive learning. In the IBRE, participants learn that one pair of symptoms (AB) predicts a frequently occurring disease, whilst an overlapping pair of symptoms (AC) predicts a rarely occurring disease. Participants subsequently infer that BC predicts the rare disease, a non-rational decision made in opposition to the underlying base rates of the two diseases. Error-driven attention theories of learning state that the IBRE occurs because C attracts more attention than B. On the basis of this account we predicted and observed the occurrence of brain potentials associated with visual attention: a posterior Selection Negativity, and a concurrent anterior Selection Positivity, for C vs. B in a post-training test phase. Error-driven attention theories further predict no Selection Negativity, Selection Positivity or IBRE, for control symptoms matched on frequency to B and C, but for which there was no shared symptom (A) during training. These predictions were also confirmed, and this confirmation discounts alternative explanations of the IBRE based on the relative novelty of B and C. Further, we observed higher response accuracy for B alone than for C alone; this dissociation of response accuracy (B>C) from attentional allocation (C>B) discounts the possibility that the observed attentional difference was caused by the difference in response accuracy

Structural insight into TPX2-stimulated microtubule assembly

During mitosis and meiosis, microtubule (MT) assembly is locally upregulated by the chromatin-dependent Ran-GTP pathway. One of its key targets is the MT-associated spindle assembly factor TPX2. The molecular mechanism of how TPX2 stimulates MT assembly remains unknown because structural information about the interaction of TPX2 with MTs is lacking. Here, we determine the cryo-electron microscopy structure of a central region of TPX2 bound to the MT surface. TPX2 uses two flexibly linked elements ('ridge' and 'wedge') in a novel interaction mode to simultaneously bind across longitudinal and lateral tubulin interfaces. These MT-interacting elements overlap with the binding site of importins on TPX2. Fluorescence microscopy-based in vitro reconstitution assays reveal that this interaction mode is critical for MT binding and facilitates MT nucleation. Together, our results suggest a molecular mechanism of how the Ran-GTP gradient can regulate TPX2-dependent MT formation

Association of five Austrodanthonia species (family Poaceae) with large and small scale environmental features in central western New South Wales

Twenty-eight natural populations of Wallaby Grasses, Austrodanthonia species, in central western New South Wales were sampled and species presence related to a suite of environmental characteristics. An average of 12 plants were selectively sampled from each population; most populations consisted of at least four out of five species, Austrodanthonia bipartita, A. caespitosa, A. eriantha, A. fulva and A. setacea. Numerous ecological factors allowed the widespread co-occurrence of these closely-related species. Large-scale rainfall and climatic factors were correlated with species-presence but no universal small-scale site environmental variables were important for all species. The most widespread species was Austrodanthonia caespitosa and environmental variations at a local site scale, depending on exposure to solar radiation, may at least partially overcome regional rainfall and climate influences

Investigating the Coupling of Helicopter Aerodynamics with SIMPACK for Articulated and Hingeless Rotors

In this paper the results of a tight coupling of rotor aerodynamics with a rotor model built up in the multibody software SIMPACK are presented. The aerodynamics are calculated by S4, which is a simulation tool developed at the Institute of Flight Systems of the German Aerospace Center. In a first step, the coupling approach was verified via cross code comparison for simple load cases such as hover flight for a hingeless blade with a straight elastic axis. The conclusions drawn for the verification methodology will be pointed out in the beginning of this paper. Investigations of a four bladed rotor in trimmed forward flight condition were conducted, leading to the discovery of a drawback in the representation of flexible beam-like structures in SIMPACK for helicopter applications. Additionally, a model of the articulated 7A rotor has been created. With this rotor a high speed flight condition test case was performed in the S1 wind tunnel and the results of the simulations are compared to the test results. In an attempt to eliminate the modeling deficiencies of the one-dimensional beam, a three-dimensional finite element model of the 7A rotor blade has been built at the Institute of Aeroelasticity as well. A comparison of the eigenmodes and eigenfrequencies of the one- and three-dimensional model will be shown