U. Zimmer - Academia.edu (original) (raw)

Papers by U. Zimmer

Materials Science Forum, 1991

Proceedings of the 1998 IEEE International Symposium on Intelligent Control (ISIC) held jointly with IEEE International Symposium on Computational Intelligence in Robotics and Automation (CIRA) Intelligent Systems and Semiotics (ISAS) (Cat. No.98CH36262), 1998

This paper presents a conceptual architecture for autonomous robots that integrates behaviour-bas... more This paper presents a conceptual architecture for autonomous robots that integrates behaviour-based and goal-directed action as by following a traditional action plan. Dual Dynamics is the formalism for describing behaviourbased action. Partial-order propositional plans, which get generated by GRAPHPLAN , are used as a basis for acting goal-directedly; the concept is suitable for using other planning methods and plan representations, though. The paper presents the corresponding action and plan representations at the plan side and at the behaviour side. Moreover, it describes how behaviour-based action is biased towards executing a plan and how information from the behaviour side is fed back to the plan side to determine progress in the plan execution.

This paper describes the development of a carbon dioxide (CO 2 ) sensing rotorcraft unmanned aeri... more This paper describes the development of a carbon dioxide (CO 2 ) sensing rotorcraft unmanned aerial vehicle (RUAV) and the experiences gained throughout its development as well as during its first deployment in a CO 2 trial. The aim of the flying measurement platform is to enable the creation of detailed gas distribution maps of larger areas in a relatively short timeframe for reasonable costs.

SEG Technical Program Expanded Abstracts 2007, 2007

Monatsschrift Kinderheilkunde - MONATSSCHR KINDERHEILK, 2004

ABSTRACT Zusammenfassung Antiepileptika gelten als schwach teratogen wirkende Substanzen. In eine... more ABSTRACT Zusammenfassung Antiepileptika gelten als schwach teratogen wirkende Substanzen. In einer prospektiven Längsschnittstudie von der Geburt bis zum Jugendalter verglichen wir das Körperwachstum von Kindern, die während der Schwangerschaft gegenüber unterschiedlichen Antiepileptika exponiert gewesen waren, mit dem von Kontrollkindern, die nach Körpergröße und Sozialstatus der Eltern, Nikotinkonsum der Mutter während der Schwangerschaft sowie Parität parallelisiert worden waren. Während für die Gesamtgruppe der antiepileptikaexponierten Kinder keine Unterschiede bei den Kopfumfängen mit 1, 6 und 14 Jahren zu erkennen waren, war die Körpergröße mit 1 Jahr signifikant kleiner. In Abhängigkeit von der Therapieform und einzelnen Medikamenten zeigten sich deutlichere Unterschiede, allerdings nur bei Polytherapie oder bei Phenobarbitaltherapie (überwiegend als Polytherapie): Eine intrauterine Exposition gegenüber Polytherapie und Phenobarbitaltherapie (als Monotherapie oder als Teil einer Polytherapie) führte zu geringeren Körpermaßen. Der Einfluss einer Polytherapie und einer Phenobarbitaltherapie bei Schwangeren mit Epilepsie auf das Wachstum der Kinder hält u. E. bis ins Jugendalter an.

Neuropsychologia, 2006

The issue of where in the human cortex coding of sound location is represented still is a matter ... more The issue of where in the human cortex coding of sound location is represented still is a matter of debate. It is unclear whether there are cortical areas that are specifically activated depending on the location of sound. Are identical or distinct cortical areas in one hemisphere involved in processing of sounds from the left and right? Also, the possibility has not been investigated so far that distinct areas have a preference for processing of central and eccentric sound locations. The present study focussed on these issues by using functional magnetic resonance imaging (fMRI). Activations evoked by left, right and central sounds were analysed separately, and contrasts were computed between these conditions. We did not find areas, which were involved in the processing of exclusively left, right or central sound positions. Large overlapping areas rather were observed for the three sound stimuli, located in the temporal, parietal and frontal cortices of both hemispheres. This result argues for the idea of a widely distributed bilateral network accessing an internal representation of the body to encode stimulus position in relation to the body median plane. However, two areas (right BA 40 and left BA 37) also were found to have preferences for sound position. In particular, BA 40 turned out to be significantly more activated by processing central positions, compared to eccentric stimuli. In line with previous findings on visual perception, the latter observation supports the assumption that the right inferior parietal cortex may be preferentially involved in the perception of central stimulus positions in relation to the body.

Neuron, 2005

Our brain continuously receives complex combinations of sounds originating from different sources... more Our brain continuously receives complex combinations of sounds originating from different sources and relating to different events in the external world. Timing differences between the two ears can be used to localize sounds in space, but only when the inputs to the two ears have similar spectrotemporal profiles (high binaural coherence). We used fMRI to investigate any modulation of auditory responses by binaural coherence. We assessed how processing of these cues depends on whether spatial information is task relevant and whether brain activity correlates with subjects' localization performance. We found that activity in Heschl's gyrus increased with increasing coherence, irrespective of whether localization was task relevant. Posterior auditory regions also showed increased activity for high coherence, primarily when sound localization was required and subjects successfully localized sounds. We conclude that binaural coherence cues are processed throughout the auditory cortex and that these cues are used in posterior regions for successful auditory localization.

NeuroImage, 2009

The perception of movement in the auditory modality requires dynamic changes in the input that re... more The perception of movement in the auditory modality requires dynamic changes in the input that reaches the two ears (e.g. sequential changes of interaural time differences; dynamic ITDs). However, it is still unclear as to what extent these temporal cues interact with other interaural cues to determine successful movement perception, and which brain regions are involved in sound movement processing. Here, we presented trains of white-noise bursts containing either static or dynamic ITDs, and we varied parametrically the level of binaural coherence (BC) of both types of stimuli. Behaviorally, we found that movement discrimination sensitivity decreased with decreasing levels of BC. fMRI analyses highlighted a network of temporal, frontal and parietal regions where activity decreased with decreasing BC. Critically, in the intra-parietal sulcus and the supra-marginal gyrus brain activity decreased with decreasing BC, but only for dynamic-ITD sounds (BC by ITD interaction). Thus, these regions activated selectively when the sounds contained both dynamic ITDs and high levels of BC; i.e. when subjects perceived sound movement. We conclude that sound movement perception requires both dynamic changes of the auditory input and effective sound-source localization, and that parietal cortex utilizes interaural temporal and coherence cues for the successful perception of sound movement.

European Journal of Neuroscience, 2010

Previously, we have shown that spatial attention to a visual stimulus can spread across both spac... more Previously, we have shown that spatial attention to a visual stimulus can spread across both space and modality to a synchronously presented but task-irrelevant sound arising from a different location, reflected by a late-onsetting, sustained, negative-polarity event-related potential (ERP) wave over fronto-central scalp sites, likely originating in part from the auditory cortices. Here we explore the influence of cross-modal conflict on the amplitude and temporal dynamics of this multisensory spreading-of-attention activity. Subjects attended selectively to one of two concurrently presented lateral visual-letter streams to perform a sequential comparison task, while ignoring task-irrelevant, centrally presented spoken letters that could occur synchronously with either the attended or unattended lateral visual letters and could be either congruent or incongruent with them. Extracted auditory ERPs revealed that, collapsed across congruency, attentional spreading across modalities started around 220 ms, replicating our earlier findings. The interaction between attentional spreading and conflict occurred beginning at around 300 ms, with attentionalspreading activity being larger for incongruent trials. Thus, the increased processing of an incongruent, task-irrelevant sound in a multisensory stimulation appear to occur some time after attention has spread from the attended visual part to the ignored auditory part, presumably reflecting that the conflict detection and associated attentional capture occurs after the accrual of some multisensory interaction processes at a higher-level semantic processing stage.

European Journal of Neuroscience, 2004

The integration of auditory and visual spatial information is an important prerequisite for accur... more The integration of auditory and visual spatial information is an important prerequisite for accurate orientation in the environment. However, while visual spatial information is based on retinal coordinates, the auditory system receives information on sound location in relation to the head. Thus, any deviation of the eyes from a central position results in a divergence between the retinal visual and the head-centred auditory coordinates. It has been suggested that this divergence is compensated for by a neural coordinate transformation, using a signal of eye-in-head position. Using functional magnetic resonance imaging, we investigated which cortical areas of the human brain participate in such auditory-visual coordinate transformations. Sounds were produced with different interaural level differences, leading to left, right or central intracranial percepts, while subjects directed their gaze to visual targets presented to the left, to the right or straight ahead. When gaze was to the left or right, we found the primary visual cortex (V1 ⁄ V2) activated in both hemispheres. The occipital activation did not occur with sound lateralization per se, but was found exclusively in combination with eccentric eye positions. This result suggests a relation of neural processing in the visual cortex and the transformation of auditory spatial coordinates responsible for maintaining the perceptual alignment of audition and vision with changes in gaze direction.

European Journal of Neuroscience, 2007

Tactile stimuli at the same location as a visual target can increase activity in the contralatera... more Tactile stimuli at the same location as a visual target can increase activity in the contralateral occipital cortex compared with spatially incongruent bimodal stimulation. Does this cross-modal congruency effect in the visual cortex depend on available cognitive resources? Visual attention and working memory can modulate responses to visual stimuli in the occipital cortex, with attenuation in conditions of high-attentional or low-memory load. Here, we asked if these two cognitive factors affect multisensory processing in the visual cortex. Using functional magnetic resonance imaging in humans, we manipulated the load of working memory or visuo-spatial attention. Concurrently with these primary tasks we presented same-side (congruent) or opposite-side (incongruent) visuo-tactile stimuli. Both experiments revealed enhancement of brain activity for congruent vs incongruent bimodal stimulation in the contralateral occipital cortex. Critically, these cross-modal effects occurred irrespective of the level of load. We conclude that processing of visuotactile spatial congruency in the visual cortex does not depend on available visuo-spatial and memory resources.

Cognitive Processing, 2006

OCEANS 2006 - Asia Pacific, 2006

ABSTRACT Effective communication mechanisms in schools of submersibles are a key requirement for ... more ABSTRACT Effective communication mechanisms in schools of submersibles are a key requirement for their meaningful deployment. Furthermore a fully distributed communication schema is preferable for reasons of reliability. The required communication form is usually many-to-many, especially omnicast [4] (or gossiping ). All these constraints are hard to achieve at the same time in a low-bandwidth, short range communication setup. The theoretical findings in [4] and [5] are expanded and employed for the actual underwater schools communication in the Serafina project (e.g. [2], [3]). The results are reported here.

Springer Tracts in Advanced Robotics, 2008

ABSTRACT Continuous relative localization among all local members of a school of submarines is an... more ABSTRACT Continuous relative localization among all local members of a school of submarines is an essential pre-condition for distributed motion control. Exploiting the short-range, underwater electromagnetic as well as the acoustical channel, the proposed approach delivers sufficient bearing, range and posture estimations based on local sensing in small, autonomous submersibles with limited energy capacities and computational resources. This research is part of the Serafina project at the Australian National University, aiming for large schools of autonomous underwater vehicles. Results of a number of physical experiments are presented which tests for precision, sensing range, interference robustness, and motion sensitivity.