F Blankenburg, Christian Ruff, R Deichmann, G Rees, J Driver, The cutaneous rabbit illusion affects human primary sensory cortex somatotopically, PLoS Biology, Vol. 4 (3), 2006. (Journal Article)
We used functional magnetic resonance imaging (fMRI) to study neural correlates of a robust somatosensory illusion that can dissociate tactile perception from physical stimulation. Repeated rapid stimulation at the wrist, then near the elbow, can create the illusion of touches at intervening locations along the arm, as if a rabbit hopped along it. We examined brain activity in humans using fMRI, with improved spatial resolution, during this version of the classic cutaneous rabbit illusion. As compared with control stimulation at the same skin sites (but in a different order that did not induce the illusion), illusory sequences activated contralateral primary somatosensory cortex, at a somatotopic location corresponding to the filled-in illusory perception on the forearm. Moreover, the amplitude of this somatosensory activation was comparable to that for veridical stimulation including the intervening position on the arm. The illusion additionally activated areas of premotor and prefrontal cortex. These results provide direct evidence that illusory somatosensory percepts can affect primary somatosensory cortex in a manner that corresponds somatotopically to the illusory percept. |
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G R Fink, Z M Manjaly, Klaas Enno Stephan, J M Gurd, K Zilles, K Amunts, J C Marshall, A role for Broca's area beyond language processing: Evidence from neuropsychology and fMRI, In: Broca's Region, Oxford University Press, Oxford, UK, p. 254 - 269, 2006. (Book Chapter)
Broca's area (or, more generally, the left inferior frontal region) is implicated in many language and language-related tasks. This chapter addresses the question of whether it is legitimate to move from this assertion (supported by very large numbers of lesion studies and functional neuroimaging experiments) to the theoretical claim that the exclusive (or even the core) specialization of Broca's area is the mediation of language functions. It shows that particular neuroanatomical regions, including Broca's area, change their functions consequent upon the simultaneous activation of other regions that are effectively connected to a given region. |
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E Rounis, Klaas Enno Stephan, L Lee, H R Siebner, A Pesenti, K J Friston, J C Rothwell, R S J Frackowiak, Acute changes in frontoparietal activity after repetitive transcranial magnetic stimulation over the dorsolateral prefrontal cortex in a cued reaction time task, Journal of Neuroscience, Vol. 26 (38), 2006. (Journal Article)
Lesion and functional imaging studies in humans have suggested that the dorsolateral prefrontal cortex (DLPFC), ventrolateral prefrontal cortex (VLPFC), and intraparietal sulcus (IPS) are involved in orienting attention. A functional magnetic resonance imaging study supplemented by a behavioral experiment examined the effects of 5 Hz repetitive transcranial magnetic stimulation (rTMS) conditioning to the right and left DLPFC on reaction times and synaptic activity as indexed by changes in the blood oxygenation level-dependent (BOLD) signal during a cued choice reaction time task. Orienting precues were either correct (valid) or incorrect (invalid) with respect to the subsequent move cue. The effects of real and sham rTMS were compared for each site of stimulation. Invalid trials showed a significant increase in response times and increases in the BOLD signal in right frontal and parietal regions when compared with valid trials. Conditioning left DLPFC with rTMS led to decreased BOLD signal during performance of this reorienting task in areas including left VLPFC and left IPS. Comparing invalid to valid trials after right DLPFC conditioning revealed decreased BOLD signal in right VLPFC. Data from the behavioral study showed that right DLPFC rTMS selectively increases response times in invalid trials. This effect was only present in the first 10 min after rTMS conditioning. No effect was found in either validly or invalidly cued trials with left DLPFC conditioning. These results suggest that 5 Hz rTMS over right DLPFC exerts remote effects on the activity of areas that functionally interact with the DLPFC during attentional processes, particularly when the reorienting of attention is more demanding as in invalid trials. |
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K Wiech, R Kalisch, N Weiskopf, B Pleger, Klaas Enno Stephan, R J Dolan, Anterolateral prefrontal cortex mediates the analgesic effect of expected and perceived control over pain, Journal of Neuroscience, Vol. 26 (44), 2006. (Journal Article)
Perceived control attenuates pain and pain-directed anxiety, possibly because it changes the emotional appraisal of pain. We examined whether brain areas associated with voluntary reappraisal of emotional experiences also mediate the analgesic effect of perceived control over pain. Using functional magnetic resonance imaging, we compared self-controlled noxious stimuli with physically identical stimuli that were externally controlled. Self-controlled stimulation was accompanied by less pain and anxiety and higher activation in dorsal anterior cingulate (dACC), right dorsolateral, and bilateral anterolateral prefrontal (alPFC) cortices. Activation in dACC and right alPFC was negatively correlated with pain intensity ratings. For externally controlled pain, activation in right alPFC was inversely correlated with the participants' general belief to have control over their lives. Our results are consistent with a reappraisal view of control and suggest that the analgesic effect of perceived control relies on activation of right alPFC. Failure to activate right alPFC may explain the maladaptive effects of strong general control beliefs during uncontrollable pain. |
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R Kalisch, E Korenfeld, Klaas Enno Stephan, N Weiskopf, B Seymour, R J Dolan, Context-dependent human extinction memory is mediated by a ventromedial prefrontal and hippocampal network, Journal of Neuroscience, Vol. 26 (37), 2006. (Journal Article)
In fear extinction, an animal learns that a conditioned stimulus (CS) no longer predicts a noxious stimulus [unconditioned stimulus (UCS)] to which it had previously been associated, leading to inhibition of the conditioned response (CR). Extinction creates a new CS-noUCS memory trace, competing with the initial fear (CS-UCS) memory. Recall of extinction memory and, hence, CR inhibition at later CS encounters is facilitated by contextual stimuli present during extinction training. In line with theoretical predictions derived from animal studies, we show that, after extinction, a CS-evoked engagement of human ventromedial prefrontal cortex (VMPFC) and hippocampus is context dependent, being expressed in an extinction, but not a conditioning, context. Likewise, a positive correlation between VMPFC and hippocampal activity is extinction context dependent. Thus, a VMPFC-hippocampal network provides for context-dependent recall of human extinction memory, consistent with a view that hippocampus confers context dependence on VMPFC. |
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T Singer, B Seymour, J P O'Doherty, Klaas Enno Stephan, R J Dolan, C D Frith, Empathic neural responses are modulated by the perceived fairness of others, Nature, Vol. 439 (7075), 2006. (Journal Article)
The neural processes underlying empathy are a subject of intense interest within the social neurosciences. However, very little is known about how brain empathic responses are modulated by the affective link between individuals. We show here that empathic responses are modulated by learned preferences, a result consistent with economic models of social preferences. We engaged male and female volunteers in an economic game, in which two confederates played fairly or unfairly, and then measured brain activity with functional magnetic resonance imaging while these same volunteers observed the confederates receiving pain. Both sexes exhibited empathy-related activation in pain-related brain areas (fronto-insular and anterior cingulate cortices) towards fair players. However, these empathy-related responses were significantly reduced in males when observing an unfair person receiving pain. This effect was accompanied by increased activation in reward-related areas, correlated with an expressed desire for revenge. We conclude that in men (at least) empathic responses are shaped by valuation of other people's social behaviour, such that they empathize with fair opponents while favouring the physical punishment of unfair opponents, a finding that echoes recent evidence for altruistic punishment. |
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Klaas Enno Stephan, J Mattout, O David, K J Friston, Models of functional neuroimaging data, Current Medical Imaging Reviews, Vol. 2 (1), 2006. (Journal Article)
Inferences about brain function, using functional neuroimaging data, require models of how the data were caused. A variety of models are used in practice that range from conceptual models of functional anatomy to nonlinear mathematical models of hemodynamic responses (e.g. as measured by functional magnetic resonance imaging, fMRI) and neuronal responses. In this review, we discuss the most important models used to analyse functional imaging data and demonstrate how they are interrelated. Initially, we briefly review the anatomical foundations of current theories of brain function on which all mathematical models rest. We then introduce some basic statistical models (e.g. the general linear model) used for making classical (i.e. frequentist) and Bayesian inferences about where neuronal responses are expressed. The more challenging question, how these responses are caused, is addressed by models that incorporate biophysical constraints (e.g. forward models from the neural to the hemodynamic level) and/or consider causal interactions between several regions, i.e. models of effective connectivity. Some of the most refined models to date are neuronal mass models of electroencephalographic (EEG) responses. These models enable mechanistic inferences about how evoked responses are caused, at the level of neuronal subpopulations and the coupling among them. |
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T Baldeweg, D Wong, Klaas Enno Stephan, Nicotinic modulation of human auditory sensory memory: Evidence from mismatch negativity potentials, International Journal of Psychophysiology, Vol. 59 (1), 2006. (Journal Article)
Impairment in mismatch negativity (MMN) generation is a robust biological marker of schizophrenia. Understanding the physiological and pharmacological processes involved in its generation may therefore advance our understanding of this complex disorder. The present study tested if acute administration of nicotine modulates human auditory sensory memory as measured with MMN. ERP responses to tone duration deviants were recorded using a stimulation protocol with continuously changing (roving) standard stimuli in order to measure the effect of stimulus repetitions on encoding of new stimuli (MMN memory trace effect). Twenty healthy adult volunteers were randomly assigned to receive either a nicotine gum or placebo after a baseline ERP recording. Nicotine administration augmented MMN amplitude in the treatment group compared to the baseline recording, while no MMN change was found in the placebo group. The drug effect was due to a selective enhancement of a frontal positive potential to standard stimuli (from 80-200 ms post-stimulus), while the negativity to deviants remained unaffected. Furthermore, under nicotine stimulation this repetition positivity showed a more marked increase with stimulus repetition compared to baseline and placebo. These results have potential implications for schizophrenia by suggesting that nicotinic agonists could ameliorate patients' MMN deficits by improving stimulus encoding and sensory memory trace formation. |
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Klaas Enno Stephan, T Baldeweg, K J Friston, Synaptic plasticity and dysconnection in schizophrenia, Biological Psychiatry, Vol. 59 (10), 2006. (Journal Article)
Current pathophysiological theories of schizophrenia highlight the role of altered brain connectivity. This dysconnectivity could manifest 1) anatomically, through structural changes of association fibers at the cellular level, and/or 2) functionally, through aberrant control of synaptic plasticity at the synaptic level. In this article, we review the evidence for these theories, focusing on the modulation of synaptic plasticity. In particular, we discuss how dysconnectivity, observed between brain regions in schizophrenic patients, could result from abnormal modulation of N-methyl-D-aspartate (NMDA)-dependent plasticity by other neurotransmitter systems. We focus on the implication of the dysconnection hypothesis for functional imaging at the systems level. In particular, we review recent advances in measuring plasticity in the human brain using functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) that can be used to address dysconnectivity in schizophrenia. Promising experimental paradigms include perceptual and reinforcement learning. We describe how theoretical and causal models of brain responses might contribute to a mechanistic understanding of synaptic plasticity in schizophrenia. |
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A P R Smith, Klaas Enno Stephan, M D Rugg, R J Dolan, Task and content modulate amygdala-hippocampal connectivity in emotional retrieval, Neuron, Vol. 49 (4), 2006. (Journal Article)
The ability to remember emotional events is crucial for adapting to biologically and socially significant situations. Little is known, however, about the nature of the neural interactions supporting the integration of mnemonic and emotional information. Using fMRI and dynamic models of effective connectivity, we examined regional neural activity and specific interactions between brain regions during a contextual memory retrieval task. We independently manipulated emotional context and relevance of retrieved emotional information to task demands. We show that retrieval of emotionally valenced contextual information is associated with enhanced connectivity from hippocampus to amygdala, structures crucially involved with encoding of emotional events. When retrieval of emotional information is relevant to current behavior, amygdala-hippocampal connectivity increases bidirectionally, under modulatory influences from orbitofrontal cortex, a region implicated in representation of affective value and behavioral guidance. Our findings demonstrate that both memory content and behavioral context impact upon large scale neuronal dynamics underlying emotional retrieval. |
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M D Hesse, C M Thiel, Klaas Enno Stephan, G R Fink, The left parietal cortex and motor intention: an event-related functional magnetic resonance imaging study, Neuroscience, Vol. 140 (4), 2006. (Journal Article)
Traditionally the posterior parietal cortex was believed to be a sensory structure. More recently, however, its important role in sensory-motor integration has been recognized. One of its functions suggested in this context is the forming of intentions, i.e. high-level cognitive plans for movements. The selection and planning of a specific movement defines motor intention. In this study we used rapid event-related functional magnetic resonance imaging of healthy human subjects to investigate the involvement of posterior parietal cortex in motor intention in response to valid imperative cues. Subjects were provided with either neutral, motor or spatial cues. Neutral cues simply alerted, motor cues indicated which hand to use for response, and spatial cues indicated on which side the target would appear. Importantly, identical targets and responses followed these cues. Therefore any differential neural effects observed are independent from the actual movement performed. Differential blood oxygen level dependent signal changes for motor vs. neutral as well as motor vs. spatial cue trials were found in the left supramarginal gyrus, as hypothesized. The results demonstrate that neural activity in the left supramarginal gyrus underlies motor plans independent from the execution of the movement and thus extend previous neuropsychological and functional imaging data on the role of the left supramarginal gyrus in higher motor cognition. |
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Helmut Max Dietl, Andreas Grütter, Martin Lutzenberger, Governance, innovation, and strategies in deregulated postal markets, In: Governance Innovations and Strategies, Gabler Verlag / Springer, Wiesbaden, p. 145 - 164, 2006. (Book Chapter)
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Hans Moser, Reto Eberle, Revisionsstelle und Unternehmensführung - wie wird kommuniziert?: Berichterstattung an den Verwaltungsrat und an die Generalversammlung, Der Schweizer Treuhänder, Vol. 80 (5), 2006. (Journal Article)
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Konstantin Beck, Walter Krämer, Weyma Lübbe, Bettina Müller, Holger Pfaff, Joachim L Schultze, Protokoll einer Podiumsdiskussion, In: Prävention auf dem Prüfstand : wieviel organisierte Gesundheit - wieviel Eigenverantwortung? : "...und ein langes gesundes Leben", Köln, p. 60 - 85, 2006. (Book Chapter)
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Verena Gelpke, Konstantin Beck, Wolfgang Schweiger, Kundenwertanalyse: Eine schwierige Problematik – aber es gibt auch Erfolge!, Planung und Analyse, Vol. 2, 2006. (Journal Article)
Welche Faktoren entscheiden darüber, dass ein Kundenwert letztendlich so eingeführt werden kann, dass der Verkauf ihn als strategisches Verkaufs-Instrument erfolgswirksam zu nutzen vermag? Zu nennen sind vorausschauende Planung, systematische Bestimmung der Anforderungen und sorgfältige, auf die Anforderungen abgestimmte mathematische Formulierung der Berechnung. Weiter stellen der zielgerichtete Einbezug eines Data-Warehouses, eine akkurate statistische Modellierung, rasche und umsichtige Implementierung und vor allem eine detaillierte und fundierte Schulung des Außendienstes durch Marketingmitarbeiter wichtige Erfolgskriterien dar. Nach der ersten Implementierung ist es wichtig, das Projekt noch nicht als abgeschlossen zu betrachten, denn noch fehlt der Feinschliff. Dazu gehört die selbstkritische Überprüfung und nötigenfalls Verbesserung der Berechnung, sowie die Optimierung der Berechnungsperiodizität. Die kontinuierliche Schulung muss ebenfalls beibehalten werden, damit der Feedback generierende Kontakt zum Außendienst nicht abbricht. Aber auch gezielte Kommunikation bei den strategischen Organen des Unternehmens ist notwendig, um die Akzeptanz des Kundenwerts auf allen hierarchischen Stufen sicher zu stellen. Die konsequente Beachtung all dieser Prozessschritte war der Grund dafür, dass die vorliegende Case Study zur Erfolgsgeschichte wurde. |
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Konstantin Beck, Maria Trottmann, Urs Käser, Bernhard Keller, Stefan Von Rotz, Peter Zweifel, Nachhaltige Gestaltung des Risikoausgleichs in der Schweizer Krankenversicherung, hep, Bern, 2006. (Book/Research Monograph)
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Marek Pycia, Marek G Pycia, Linear functional inequalities: a general theory and new special cases, Dissertationes Mathematicae, Vol. 438, 2006. (Journal Article)
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André C. Wohlgemuth, Urs Peter Hinnen, Unternehmensberatung im Einsatz gegen Korruptionsfolgen: Fallstudie aus dem öffentlichen Bereich, Unternehmensberater, Vol. 9 (6), 2005. (Journal Article)
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Christian Seybold, Martin Glinz, Silvio Meier, Simulation-based Validation and Defect Localization for Evolving, Semi-Formal Requirements Models, In: 12th Asia-Pacific Software Engineering Conference (APSEC 2005), December 2005. (Conference or Workshop Paper published in Proceedings)
When requirements models are developed in an iterative
and evolutionary way, requirements validation becomes a
major problem. In order to detect and fix problems early,
the specification should be validated as early as possible,
and should also be revalidated after each evolutionary step.
In this paper, we show how the ideas of continuous integration
and automatic regression testing in the field of coding
can be adapted for simulation-based, automatic revalidation
of requirements models after each incremental step.
While the basic idea is fairly obvious, we are confronted
with a major obstacle: requirements models under development
are incomplete and semi-formal most of the time,
while classic simulation approaches require complete, formal
models. We present how we can simulate incomplete,
semi-formal models by interactively recording missing behavior
or functionality.
However, regression simulations must run automatically
and do not permit interactivity. We therefore have developed
a technique where the simulation engine automatically
resorts to the interactively recorded behavior in those cases
where it does not get enough information from the model
during a regression simulation run.
Finally, we demonstrate how the information gained
from model evolution and regression simulation can be exploited
for locating defects in the model. |
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Daniel Fasnacht, The Transition to Open Innovation: A Case Study in the Banking Industry, University of Nottingham, Faculty of Social Sciences, 2005. (Dissertation)
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