2,132 research outputs found
An induction proof of the backpropagation algorithm in matrix notation
No full textCode repository for Ostwald & Usée "An induction proof of the backpropagation algorithm in matrix notation
Voxel-wise information theoretic EEG-fMRI feature integration
No full textWe have recently proposed the evaluation of a set of information theoretic quantities (ITQs) for the integration of simultaneously acquired EEG-fMRI data (Ostwald, D., Porcaro, C., Bagshaw, A.P., 2010. An information theoretic approach to EEG-fMRI integration of visually evoked responses. Neuroimage. 49, 498-516). In our previous experimental evaluation of the information theoretic framework, we defined the data subsets from which to calculate the ITQs using a priori constraints. In the case of EEG, this meant that data were extracted from a single electrode, while for fMRI the analysed data came from voxels contained within a sphere surrounding the most responsive voxel of visual cortex. While this approach was a natural starting point for the evaluation of the framework in the application to combined EEG-fMRI data sets, a more principled approach to data selection is desirable. Here, we propose to combine standard fMRI data pre-processing and low-resolution electromagnetic tomography (LORETA) for the evaluation of ITQs across the entire three-dimensional brain space. We apply the proposed method to a simultaneous EEG-fMRI data set acquired during checkerboard stimulation and assess the topographical informativeness of EEG (time and frequency domain) and fMRI features with respect to the stimulus and each other. The resulting information theoretic effect size maps are supplemented with a statistical evaluation based on Gaussian null model simulations using a false-discovery rate procedure. Given the contamination of EEG recordings by artefacts induced by the MR scanning environment we further assessed the influence of different advanced EEG pre-processing methods (independent component analysis and functional source separation) on the information topography. The results of this analysis provide evidence for the topographically focussed informativeness of both EEG and fMRI features with respect to the stimulus, but for the current feature selection do not detect EEG-fMRI activity dependence. More advanced EEG data pre-processing rendered the feature distributions more stimulus-informative, but did not alter the EEG-fMRI activity and conditional dependencies
An induction proof of the backpropagation algorithm in matrix notation
No full textCode repository for Ostwald & Usée "An induction proof of the backpropagation algorithm in matrix notation
Power, positive predictive value, and sample size calculations for random field theory-based fMRI inference
No full textThis project contains data and code related to Ostwald et al. (2019) Power, positive predictive value, and sample size calculations for random field theory-based fMRI inference
Variational Bayesian parameter estimation techniques for the general linear model
No full textThis project contains the Matlab code and data associated with Starke and Ostwald (2017) 'Variational Bayesian parameter estimation techniques for the general linear model
EEG-fMRI based information theoretic characterization of the human perceptual decision system.
No full textThe modern metaphor of the brain is that of a dynamic information processing device. In the current study we investigate how a core cognitive network of the human brain, the perceptual decision system, can be characterized regarding its spatiotemporal representation of task-relevant information. We capitalize on a recently developed information theoretic framework for the analysis of simultaneously acquired electroencephalography (EEG) and functional magnetic resonance imaging data (fMRI) (Ostwald et al. (2010), NeuroImage 49: 498-516). We show how this framework naturally extends from previous validations in the sensory to the cognitive domain and how it enables the economic description of neural spatiotemporal information encoding. Specifically, based on simultaneous EEG-fMRI data features from n = 13 observers performing a visual perceptual decision task, we demonstrate how the information theoretic framework is able to reproduce earlier findings on the neurobiological underpinnings of perceptual decisions from the response signal features' marginal distributions. Furthermore, using the joint EEG-fMRI feature distribution, we provide novel evidence for a highly distributed and dynamic encoding of task-relevant information in the human brain
The Psychometric Construction of Empathy: An exploratory factor analysis of German empathy self-rating subscale sum scores
No full textData and Code of Groh and Ostwald (2024
The Psychometric Construction of Empathy: An exploratory factor analysis of German empathy self-rating subscale sum scores
No full textData and Code of Groh and Ostwald (2024
Computing Integrated Information
No full textThis project contains the Matlab code and data associated with Krohn and Ostwald (2017) 'Computing Integrated Information'
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