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Changing meaning causes coupling changes within higher levels of the cortical hierarchy

Processing of speech and nonspeech sounds occurs bilaterally within primary auditory cortex and surrounding regions of the superior temporal gyrus; however, the manner in which these regions interact during speech and nonspeech processing is not well understood. Here, we investigate the underlying neuronal architecture of the auditory system with magnetoencephalography and a mismatch...

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English / 01/01/2009

Tractography-based priors for dynamic causal models

Functional integration in the brain rests on anatomical connectivity (the presence of axonal connections) and effective connectivity (the causal influences mediated by these connections). The deployment of anatomical connections provides important constraints on effective connectivity, but does not fully determine it, because synaptic connections can be expressed functionally in a...

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English / 01/01/2009

Repetition suppression and plasticity in the human brain

The suppression of neuronal responses to a repeated event is a ubiquitous phenomenon in neuroscience. However, the underlying mechanisms remain largely unexplored. The aim of this study was to examine the temporal evolution of experience-dependent changes in connectivity induced by repeated stimuli. We recorded event-related potentials (ERPs) during frequency changes of a repeating...

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English / 01/01/2009

The social neuroscience of empathy

The phenomenon of empathy entails the ability to share the affective experiences of others. In recent years social neuroscience made considerable progress in revealing the mechanisms that enable a person to feel what another is feeling. The present review provides an in-depth and critical discussion of these findings. Consistent evidence shows that sharing the emotions of others is...

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English / 01/01/2009

The temporal dynamics of insula activity to disgust and happy facial expressions: a magnetoencephalography study

The insula has consistently been shown to be involved in processing stimuli that evoke the emotional response of disgust. Recently, its specificity for processing disgust has been challenged and a broader role of the insula in the representation of interoceptive information has been suggested. Studying the temporal dynamics of insula activation during emotional processing can...

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English / 01/01/2009

Variational Bayesian identification and prediction of stochastic nonlinear dynamic causal models

In this paper, we describe a general variational Bayesian approach for approximate inference on nonlinear stochastic dynamic models. This scheme extends established approximate inference on hidden-states to cover: (i) nonlinear evolution and observation functions, (ii) unknown parameters and (precision) hyperparameters and (iii) model comparison and prediction under uncertainty....

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English / 01/01/2009

Recognizing sequences of sequences

The brain's decoding of fast sensory streams is currently impossible to emulate, even approximately, with artificial agents. For example, robust speech recognition is relatively easy for humans but exceptionally difficult for artificial speech recognition systems. In this paper, we propose that recognition can be simplified with an internal model of how sensory input is...

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English / 01/01/2009

Reinforcement learning or active inference?

This paper questions the need for reinforcement learning or control theory when optimising behaviour. We show that it is fairly simple to teach an agent complicated and adaptive behaviours using a free-energy formulation of perception. In this formulation, agents adjust their internal states and sampling of the environment to minimize their free-energy. Such agents learn causal...

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English / 01/01/2009

Dynamic causal modelling of distributed electromagnetic responses

In this note, we describe a variant of dynamic causal modelling for evoked responses as measured with electroencephalography or magnetoencephalography (EEG and MEG). We depart from equivalent current dipole formulations of DCM, and extend it to provide spatiotemporal source estimates that are spatially distributed. The spatial model is based upon neural-field equations that model...

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English / 01/01/2009

Population dynamics under the Laplace assumption

In this paper, we describe a generic approach to modelling dynamics in neuronal populations. This approach models a full density on the states of neuronal populations but finesses this high-dimensional problem by re-formulating density dynamics in terms of ordinary differential equations on the sufficient statistics of the densities considered (c.f., the method of moments). The...

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English / 01/01/2009

MRI of cellular layers in mouse brain in vivo

Noninvasive imaging of the brain of animal models demands the detection of increasingly smaller structures by in vivo MRI. The purpose of this work was to elucidate the spatial resolution and structural contrast that can be obtained for studying the brain of C57BL/6J mice by optimized T2-weighted fast spin-echo MRI at 9.4 T. As a prerequisite for high-resolution imaging in vivo,...

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English / 01/01/2009

Functional connectivity

Functional neuroimaging techniques are used widely in cognitive neuroscience to investigate aspects of functional specialization and functional integration in the human brain. Functional integration can be characterized in two ways – functional connectivity and effective connectivity. Whereas functional connectivity describes statistical dependencies between data, effective...

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English / 01/01/2009

Funktionelle und effektive Konnektivität

Zusammenfassung

Neurophysiologische und bildgebende Verfahren zur Messung von Hirnaktivität, wie fMRI oder EEG, werden in den Neurowissenschaften eingesetzt, um Prozesse funktioneller Spezialisierung und funktioneller Integration im menschlichen Gehirn zu untersuchen. Funktionelle Integration kann auf zwei verschiedene Arten beschrieben werden: funktionelle Konnektivität und...

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Deutsch / 01/01/2009

To react or not? Technology shocks, fiscal policy and welfare in the EU-3

This paper develops a DSGE model to examine the quantitative macroeconomic implications of counter-cyclical fiscal policy for France, Germany and the UK. The model incorporates real wage rigidity and consumption habits, as the particular market failures justifying policy intervention. We subject the model to productivity shocks and allow policy instruments to react to the output gap...

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English / 01/01/2009

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