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Robert Baumgartner

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YNIMG Journal 2019 Journal Article

Impoverished auditory cues limit engagement of brain networks controlling spatial selective attention

  • Yuqi Deng
  • Inyong Choi
  • Barbara Shinn-Cunningham
  • Robert Baumgartner

Spatial selective attention enables listeners to process a signal of interest in natural settings. However, most past studies on auditory spatial attention used impoverished spatial cues: presenting competing sounds to different ears, using only interaural differences in time (ITDs) and/or intensity (IIDs), or using non-individualized head-related transfer functions (HRTFs). Here we tested the hypothesis that impoverished spatial cues impair spatial auditory attention by only weakly engaging relevant cortical networks. Eighteen normal-hearing listeners reported the content of one of two competing syllable streams simulated at roughly +30° and −30° azimuth. The competing streams consisted of syllables from two different-sex talkers. Spatialization was based on natural spatial cues (individualized HRTFs), individualized IIDs, or generic ITDs. We measured behavioral performance as well as electroencephalographic markers of selective attention. Behaviorally, subjects recalled target streams most accurately with natural cues. Neurally, spatial attention significantly modulated early evoked sensory response magnitudes only for natural cues, not in conditions using only ITDs or IIDs. Consistent with this, parietal oscillatory power in the alpha band (8–14 ​Hz; associated with filtering out distracting events from unattended directions) showed significantly less attentional modulation with isolated spatial cues than with natural cues. Our findings support the hypothesis that spatial selective attention networks are only partially engaged by impoverished spatial auditory cues. These results not only suggest that studies using unnatural spatial cues underestimate the neural effects of spatial auditory attention, they also illustrate the importance of preserving natural spatial cues in assistive listening devices to support robust attentional control.

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TCS Journal 2002 Journal Article

Propositional default logics made easier: computational complexity of model checking

  • Robert Baumgartner
  • Georg Gottlob

Liberatore and Schaerf (Proceedings of the ECAI’ 98, 1998) give a proof that model checking for propositional normal default theories is in Δ 2 P and Δ2 P[O(log n)]-hard. However, the precise complexity is left as an open problem. We solve this problem by proving that model checking for normal default theories is complete for Δ2 P[O(log n)]. This is the class of decision problems solvable in polynomial time with a logarithmic number of calls to an oracle in NP. Additionally, we analyse the computational cost of model checking w. r. t. weak extensions, stable expansions and N -expansions and take a look at the complexity of model checking for disjunction-free default theories. Furthermore, we show that not only for disjunction-free default theories, but also for a larger class of default theories, which we call default theories in extended Horn normal form, the complexity of model checking is, in the case of normal default theories, tractable. Additionally, the complexity results are used to draw some interesting conclusions on translatability issues. In particular, there exists no function from default logic into logic programming which is polynomial, faithful and modular unless coNP =Σ2 P. Finally, we give an overview of our results concerning model checking in case of disjunctive default logic and stationary default logic.

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LPAR Conference 2001 Conference Paper

The Elog Web Extraction Language

  • Robert Baumgartner
  • Sergio Flesca
  • Georg Gottlob

Abstract This paper illustrates some aspects of the visual wrapper generation tool Lixto and describes its internal declarative logic-based language Elog. In particular, it gives an example scenarioand contains a detailed description of predicates including their input/output behavior and introduces several new conditions. Additionally, entity relationship diagrams of filters and patterns are depicted and some words on the implementation are issued. Finally, some possible ramifications are discussed.

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