This file was created by the TYPO3 extension bib --- Timezone: CEST Creation date: 2024-04-20 Creation time: 02-22-51 --- Number of references 16 phdthesis Kohl2013 2013 8.42,Gehirn,SingleTrial TU Berlin PhD Thesis FKohl article Kohl2010 Physics in medicine and biology 2010 55 15 4219--30 Decomposition of evoked magnetoencephalography (MEG) data into their underlying neuronal signals is an important step in the interpretation of these measurements. Often, independent component analysis (ICA) is employed for this purpose. However, ICA can fail as for evoked MEG data the neuronal signals may not be statistically independent. We therefore consider an alternative approach based on the recently proposed shifted factor analysis model, which does not assume statistical independence of the neuronal signals. We suggest the application of this model in the time domain and present an estimation procedure based on a Taylor series expansion. We show in terms of synthetic evoked MEG data that the proposed procedure can successfully separate evoked dependent neuronal signals while standard ICA fails. Latency estimation of neuronal signals is an inherent part of the proposed procedure and we demonstrate that resulting latency estimates are superior to those obtained by a maximum likelihood method. Evoked Potentials,Humans,Magnetoencephalography,Magnetoencephalography: methods,Models, Statistical,Neurons,Neurons: cytology,SingleTrial 8.42, Gehirn, SingleTrial http://iopscience.iop.org/article/10.1088/0031-9155/55/15/002 IOP Publishing en 1361-6560 10.1088/0031-9155/55/15/002 FKohl GWübbeler DKolossa MBär ROrglmeister CElster article Leistner2010 NeuroReport 2010 21 3 196--200 8.42, Gehirn SLeistner TSander GWübbeler ALink CElster GCurio LTrahms B MMackert article Sander2010 Biomedizinische Technik. Biomedical engineering 2010 55 2 65--76 Determining the centers of electrical activity in the human body and the connectivity between different centers of activity in the brain is an active area of research. To understand brain function and the nature of cardiovascular diseases requires sophisticated methods applicable to non-invasively measured bioelectric and biomagnetic data. As it is difficult to solve for all unknown parameters at once, several strains of data analysis have been developed, each trying to solve a different part of the problem and each requiring a different set of assumptions. Current trends and results from major topics of electro- and magnetoencephalographic data analysis are presented here together with the aim of stimulating research into the unification of the different approaches. The following topics are discussed: source reconstruction using detailed finite element modeling to locate sources deep in the brain; connectivity analysis for the quantification of strength and direction of information flow between activity centers, preferably incorporating an inverse solution; the conflict between the statistical independence assumption of sources and a possible connectivity; the verification and validation of results derived from non-invasively measured data through animal studies and phantom measurements. This list already indicates the benefits of a unified view. Action Potentials,Action Potentials: physiology,Animals,Brain,Brain Mapping,Brain Mapping: methods,Brain Mapping: trends,Brain: physiology,Computer Simulation,Electroencephalography,Electroencephalography: methods,Electroencephalography: trends,Electromagnetic Fields,Humans,Models,Neurological,Radiometry,Radiometry: methods,Radiometry: trends,SingleTrial 8.42, Gehirn http://www.degruyter.com/view/j/bmte.2010.55.issue-2/bmt.2010.027/bmt.2010.027.xml 1862-278X 10.1515/BMT.2010.027 T HSander T RKnösche ASchlögl FKohl C HWolters JHaueisen LTrahms article Link2007c Biomedizinische Technik. Biomedical engineering 2007 52 1 106--10 Two methods for single-trial analysis were compared, an established parametric template approach and a recently proposed non-parametric method based on complex bandpass filtering. The comparison was carried out by means of pseudo-real simulations based on magnetoencephalography measurements of cortical responses to auditory signals. The comparison focused on amplitude and latency estimation of the M100 response. The results show that both methods are well suited for single-trial analysis of the auditory evoked M100. While both methods performed similarly with respect to latency estimation, the non-parametric approach was observed to be more robust for amplitude estimation. The non-parametric approach can thus be recommended as an additional valuable tool for single-trial analysis. Algorithms,Auditory,Auditory: physiology,Computer-Assisted,Computer-Assisted: methods,Diagnosis, Computer-Assisted,Diagnosis, Computer-Assisted: methods,Electroencephalography,Electroencephalography: methods,Evoked Potentials, Auditory,Evoked Potentials, Auditory: physiology,Likelihood Functions,Reproducibility of Results,Sample Size,Sensitivity and Specificity,Signal Processing, Computer-Assisted 8.42, Gehirn http://www.ncbi.nlm.nih.gov/pubmed/17313344 0013-5585 10.1515/BMT.2007.020 ALink MBurghoff ASalajegheh DPoeppel LTrahms CElster article Wubbeler2007a Physics in medicine and biology 2007 52 15 4383--92 Appropriate spatial filtering followed by temporal filtering is well suited for the single-trial analysis of multi-channel magnetoencephalogram or electroencephalogram recordings. This is demonstrated by the results of a single-trial latency analysis obtained for auditory evoked M100 responses from nine subjects using two different stimulation frequencies. Spatial filters were derived automatically from the data via noise-adjusted principle component analysis, and single-trial latencies were estimated from the signal phase after complex bandpass filtering. For each of the two stimulation frequencies, estimated single-trial latencies were consistent with results obtained from a standard approach using averaged evoked responses. The quality of the estimated single-trial latencies was additionally assessed by their ability to separate between the two different stimulation frequencies. As a result, more than 80<prt>%</prt> of the single trials can be classified correctly by their estimated latencies. Acoustic Stimulation,Acoustic Stimulation: methods,Algorithms,Diagnosis, Computer-Assisted,Diagnosis, Computer-Assisted: methods,Evoked Potentials, Auditory,Evoked Potentials, Auditory: physiology,Humans,Magnetoencephalography,Magnetoencephalography: methods,Pitch Perception,Pitch Perception: physiology,Reaction Time,Reaction Time: physiology,Reproducibility of Results,Sensitivity and Specificity 8.42, Gehirn http://www.ncbi.nlm.nih.gov/pubmed/17634639 0031-9155 10.1088/0031-9155/52/15/002 GWübbeler ALink MBurghoff LTrahms CElster article Leistner2006 Neuroscience letters 2006 394 1 42--7 Functional neuroimaging techniques map neuronal activation indirectly via local concomitant cortical vascular/metabolic changes. In a complementary approach, DC-magnetoencephalography measures neuronal activation dynamics directly, notably in a time range of the slow vascular/metabolic response. Here, using this technique neuronal activation dynamics and patterns for simple and complex finger movements are characterized intraindividually: in 6/6 right-handed subjects contralateral prolonged (30 s each) complex self-paced sequential finger movements revealed stronger field amplitudes over the pericentral sensorimotor cortex than simple movements. A consistent lateralization for contralateral versus ipsilateral finger movements was not found (4/6). A subsequent sensory paradigm focused on somatosensory afferences during the motor tasks and the reliability of the measuring technique. In all six subjects stable sustained neuronal activation during electrical median nerve stimulation was recorded. These neuronal quasi-tonic activation characteristics provide a new non-invasive neurophysiological measure to interpret signals mapped by functional neuroimaging techniques. Adult,Brain Mapping,Evoked Potentials, Somatosensory,Evoked Potentials, Somatosensory: physiology,Evoked Potentials, Somatosensory: radiation effect,Female,Fingers,Fingers: physiology,Functional Laterality,Functional Laterality: physiology,Humans,Magnetoencephalography,Male,Motor Cortex,Motor Cortex: physiology,Motor Cortex: radiation effects,Movement,Movement: physiology,Movement: radiation effects,Psychomotor Performance,Psychomotor Performance: physiology,Psychomotor Performance: radiation effects,Somatosensory,Somatosensory: physiology,Somatosensory: radiation effect 8.42, Gehirn http://www.sciencedirect.com/science/article/pii/S0304394005011523 0304-3940 10.1016/j.neulet.2005.10.004 SLeistner GWübbeler LTrahms GCurio B MMackert inproceedings Wuebbeler2006c 2006 8.42, Gehirn Proc. Biomed. Tech. GWübbeler ALink MBurghoff LTrahms CElster article Burghoff2005 Physics in medicine and biology 2005 50 3 N43--8 The phase of the complex output of a narrow band Gaussian filter is taken to define the latency of the auditory evoked response M100 recorded by magnetoencephalography. It is demonstrated that this definition is consistent with the conventional peak latency. Moreover, it provides a tool for reducing the number of averages needed for a reliable estimation of the latency. Single-event latencies obtained by this procedure can be used to improve the signal quality of the conventional average by latency adjusted averaging. Evoked Potentials, Auditory,Magnetoencephalography,Magnetoencephalography: methods,Models, Theoretical,Normal Distribution,Time Factors 8.42, Gehirn http://www.ncbi.nlm.nih.gov/pubmed/15773733 0031-9155 10.1088/0031-9155/50/3/N04 MBurghoff ALink ASalajegheh CElster DPoeppel LTrahms article Link2004c Biomedizinische Technik 2004 49 2 306 8.42, Gehirn http://www.zbmed.de/ccmedimages/2004/47249.pdf ALink CElster MBurghoff LTrahms article Salajegheh2004 NeuroImage 2004 23 1 288 - 295 Standard analyses of neurophysiologically evoked response data rely on signal averaging across many epochs associated with specific events. The amplitudes and latencies of these averaged events are subsequently interpreted in the context of the given perceptual, motor, or cognitive tasks. Can such critical timing properties of event-related responses be recovered from single-trial data? Here, we make use of the <prt>M100</prt> latency paradigm used in previous magnetoencephalography (MEG) research to evaluate a novel single-trial analysis approach. Specifically, the latency of the auditory evoked <prt>M100</prt> varies systematically with stimulus frequency over a well-defined time range (lower frequencies, e.g., 125 Hz, yield up to 25 ms longer latencies than higher frequencies, e.g., 1000 Hz). Here, we show that the complex filtering approach to single-trial analysis recovers this key characteristic of the <prt>M100</prt> response, as well as some other important response properties relating to lateralization. The results illustrate (i) the utility of the complex filtering method and (ii) the potential of the <prt>M100</prt> latency to be used for stimulus encoding, since the relevant variation can be observed in single trials. Single-trial EP analysis 8.42, Gehirn http://www.sciencedirect.com/science/article/pii/S1053811904003015 1053-8119 10.1016/j.neuroimage.2004.05.022 ASalajegheh ALink CElster MBurghoff TSander LTrahms DPoeppel article Link2003 Biomedizinische Technik 2003 48 1 8.42, Gehirn http://dx.doi.org/10.1515/bmte.2003.48.s1.182 10.1515/bmte.2003.48.s1.182 ALink CElster TSander ALueschow GCurio LTrahms article Link2002 Biomedizinische Technik 2002 47 1 8.42, Gehirn 10.1515/bmte.2002.47.s1b.577 ALink CElster TSander ALueschow GCurio LTrahms article Mackert2001 Neuroreport 2001 12 8 1689-92 8.42,Gehirn 10.1097/00001756-200106130-00034 B MMackert GWübbeler SLeistner LTrahms GCurio article Wuebbeler2000 Biomedical Engineering, IEEE Transactions on 2000 47 5 594-599 We apply a recently developed multivariate statistical data analysis technique-so called blind source separation (BSS) by independent component analysis-to process magnetoencephalogram recordings of near-DC fields. The extraction of near-DC fields from MEG recordings has great relevance for medical applications since slowly varying DC-phenomena have been found, e.g., in cerebral anoxia and spreading depression in animals. Comparing several BSS approaches, it turns out that an algorithm based on temporal decorrelation successfully extracted a DC-component which was induced in the auditory cortex by presentation of music. The task is challenging because of the limited amount of available data and the corruption by outliers, which makes it an interesting real-world testbed for studying the robustness of ICA methods. decorrelation;feature extraction;hearing;magnetoencephalography;medical signal processing;music;statistical analysis;DC-component;ICA method robustness;MEG recordings;animals;auditory cortex;blind source separation;cerebral anoxia;humans;independent component analysis;magnetoencephalogram recordings;medical applications;multivariate statistical data analysis technique;music;near-DC field extraction;noninvasively recorded cortical magnetic DC-fields;outlier;real-world testbed;slowly varying DC-phenomena;spreading depression;temporal decorrelation;Blind source separation;Data analysis;Data mining;Humans;Independent component analysis;Magnetic analysis;Magnetic recording;Magnetic separation;Medical services;Source separation;Acoustic Stimulation;Algorithms;Artifacts;Auditory Cortex;Evoked Potentials, Auditory;Humans;Magnetoencephalography;Signal Processing, Computer-Assisted 8.42, Gehirn 0018-9294 10.1109/10.841331 GWübbeler AZiehe B-MMackert K-RMüller LTrahms CCurio article Mackert1999 Neuroscience Letters 1999 273 3 159--162 Recently, biomagnetic fields below 0.1 Hz arising from nerve or muscle injury currents have been measured non-invasively using superconducting quantum interference devices (SQUIDs). Here we report first long-term recordings of cortical direct current (DC) fields in humans based on a horizontal modulation (0.4 Hz) of the body and, respectively, head position beneath the sensor array: near-DC fields with amplitudes between 90 and 540 fT were detected in 5/5 subjects over the auditory cortex throughout prolonged stimulation periods (here: 30 s) during which subjects were listening to concert music. These results prove the feasibility to record non-invasively low amplitude near-DC magnetic fields of the human brain and open the perspective for studies on DC-phenomena in stroke, such as anoxic depolarization or peri-infarct depolarization, and in migraine patients. Anoxic depolarization,Auditory cortex,Direct current-magnetoencephalography,Music,Spreading depression,Superconducting quantum interference device,Sustained fields 8.42, Gehirn http://www.sciencedirect.com/science/article/pii/S0304394099006576 03043940 10.1016/S0304-3940(99)00657-6 B MMackert GWübbeler MBurghoff PMarx LTrahms GCurio