Thomas R. Knösche

Thomas R. Knösche
Max Planck Institute for Human Cognitive and Brain Sciences | CBS · EEG and MEG: Signal Analysis and Modeling-Group

Prof. Dr.

About

258
Publications
43,276
Reads
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8,104
Citations
Additional affiliations
January 2000 - present
Max Planck Institute for Human Cognitive and Brain Sciences
Position
  • Group Leader

Publications

Publications (258)
Article
Full-text available
Absolute pitch (AP) is known as the ability to recognize and label the pitch chroma of a given tone without external reference. Known brain structures and functions related to AP are mainly of macroscopic aspects. To shed light on the underlying neural mechanism of AP, we investigated the intracortical myeloarchitecture in musicians with and withou...
Article
Full-text available
In this study, we used invasive tracing to evaluate white matter tractography methods based on ex vivo diffusion-weighted magnetic resonance imaging (dwMRI) data. A representative selection of tractography methods were compared to manganese tracing on a voxel-wise basis, and a more qualitative assessment examined whether, and to what extent, certai...
Article
Full-text available
The results of brain connectivity analysis using reconstructed source time courses derived from EEG and MEG data depend on a number of algorithmic choices. While previous studies have investigated the influence of the choice of source estimation method or connectivity measure, the effects of the head modeling errors or simplifications have not been...
Article
Full-text available
In modern neuroscience there is general agreement that brain function relies on networks and that connectivity is therefore of paramount importance for brain function. Accordingly, the delineation of functional brain areas on the basis of diffusion magnetic resonance imaging (dMRI) and tractography may lead to highly relevant brain maps. Existing m...
Article
Full-text available
Diffusion MRI is a non-invasive method that potentially gives insight into the brain's white matter structure regarding the pathway of connections and properties of the axons. Here, we propose a novel global tractography method named Plausibility Tracking that provides the most plausible pathway, modeled as a smooth spline curve, between two locati...
Preprint
Full-text available
In this experimental study we demonstrate the influence of contact pressure on porcine postmortem brain tissue impedance using a movable electrode array and a load cell. We show that the variation of the contact pressure between the tissue and the measurement probe leads to a coefficient of variation in the measured impedance of under 3%. Its influ...
Article
Full-text available
Experimental and theoretical studies have shown that ephaptic coupling leads to the synchronisation and slowing down of spikes propagating along the axons within peripheral nerve bundles. However, the main focus thus far has been on a small number of identical axons, whereas realistic peripheral nerve bundles contain numerous axons with different d...
Article
Alpha power attenuation during cognitive task performing has been suggested to reflect a process of release of inhibition, increase of excitability, and thereby benefit the improvement of performance. Here, we hypothesized that changes in individual alpha power during the execution of a complex language comprehension task may correlate with the ind...
Article
Full-text available
Bradykinesia is a cardinal motor symptom in Parkinson's disease (PD), the pathophysiology of which is not fully understood. We analyzed the role of cross-frequency coupling of oscillatory cortical activity in motor impairment in PD patients and healthy controls. High-density EEG signals were recorded during various motor activities and at rest. Pat...
Article
Full-text available
As uncertainty and sensitivity analysis of complex models grows ever more important, the difficulty of their timely realizations highlights a need for more efficient numerical operations. Non-intrusive Polynomial Chaos methods are highly efficient and accurate methods of mapping input-output relationships to investigate complex models. There is sub...
Article
Full-text available
Background When modeling transcranial electrical stimulation (TES) and transcranial magnetic stimulation (TMS) in the brain, the meninges – dura, arachnoid, and pia mater – are often neglected due to high computational costs. Objective We investigate the impact of the meningeal layers on the cortical electric field in TES and TMS while considering...
Preprint
Full-text available
With the ever growing importance of uncertainty and sensitivity analysis of complex model evaluations and the difficulty of their timely realizations comes a need for more efficient numerical operations. Non-intrusive Polynomial Chaos methods are highly efficient and accurate to map input-output relationships to investigate complex models. There is...
Preprint
Full-text available
We describe a routine to precisely localize cortical muscle representations within the primary motor cortex with transcranial magnetic stimulation (TMS). This allows for an accurate and experimenter-independent determination of motor thresholds and enables TMS dosing based on individual field thresholds. Motor evoked potentials (MEPs) for different...
Preprint
Full-text available
We describe a routine to precisely localize cortical muscle representations within the primary motor cortex with transcranial magnetic stimulation (TMS) based on the functional relation between induced electric fields at the cortical level and motor evoked potentials. Besides insights into structure-function relationships, this lays the foundation...
Preprint
Full-text available
Individual differences in the ability to deal with language have long been discussed. The neural basis of these, however, is yet unknown. Here we investigated the relationship between long-range white matter connectivity of the brain, as revealed by diffusion tractography, and the ability to process syntactically complex sentences in the participan...
Article
Full-text available
Low-dimensional descriptions of spiking neural network dynamics are an effective tool for bridging different scales of organization of brain structure and function. Recent advances in deriving mean-field descriptions for networks of coupled oscillators have sparked the development of a new generation of neural mass models. Of notable interest are m...
Preprint
Full-text available
Alpha power attenuation during cognitive task performing has been suggested to reflect a process of release of inhibition, increase of excitability, and thereby benefit the improvement of performance. Here, we hypothesized that changes in individual alpha power during the execution of a complex language comprehension task may correlate with the ind...
Article
Full-text available
Transcranial magnetic stimulation (TMS) is a powerful tool to investigate causal structure-function relationships in the human brain. However, a precise delineation of the effectively stimulated neuronal populations is notoriously impeded by the widespread and complex distribution of the induced electric field. Here, we propose a method that allows...
Poster
Question. Enhanced phase amplitude coupling (PAC) between β (13–30 Hz) and broadband γ (50–150 Hz) activities has been found in surface EEG recordings from Parkinson patients at rest [1]. However, the dynamics of PAC during voluntary movement and its relationship with motor impairment of Parkinson“s disease (PD) remain unclear. Methods. Experimenta...
Preprint
Full-text available
Bradykinesia is a cardinal motor symptom in Parkinson's disease whose pathophysiology is incompletely understood. When signals are recorded from the cortex or scalp at rest, affected patients display enhanced phase-amplitude coupling between β (13-30Hz) and broadband γ (50-150Hz) oscillatory activities. However, it remains unclear whether and how a...
Article
Full-text available
The external pallidum (GPe) plays a central role for basal ganglia functions and dynamics and, consequently, has been included in most computational studies of the basal ganglia. These studies considered the GPe as a homogeneous neural population. However, experimental studies have shown that the GPe contains at least two distinct cell types (proto...
Preprint
Full-text available
We present a measurement probe consisting of four platinum electrodes fused into soda-lime glass. The probe is based on a four-terminal sensing technique that uses separate pairs of current-carrying and voltage-sensing electrodes and performs more accurate measurements than the simpler and more usual two-terminal sensing technique. The electrodes a...
Article
Full-text available
The adult human brain remains plastic even after puberty. However, whether first language (L1) training in adults can alter the language network is yet largely unknown. Thus, we conducted a longitudinal training experiment on syntactically complex German sentence comprehension. Sentence complexity was varied by the depth of the center embedded rela...
Article
Full-text available
Axonal connections are widely regarded as faithful transmitters of neuronal signals with fixed delays. The reasoning behind this is that extra-cellular potentials caused by spikes travelling along axons are too small to have an effect on other axons. Here we devise a computational framework that allows us to study the effect of extracellular potent...
Preprint
Full-text available
Low-dimensional descriptions of spiking neural network dynamics are an effective tool for bridging different scales of organization of brain structure and function. Recent advances in deriving mean-field descriptions for networks of coupled oscillators have sparked the development of a new generation of neural mass models. Of notable interest are m...
Preprint
Full-text available
The external pallidum (GPe) plays a central role for basal ganglia functions and dynamics and, consequently, has been included in most computational studies of the basal ganglia. These studies considered the GPe as a homogeneous neural population. However, experimental studies have shown that the GPe contains at least two distinct cell types (proto...
Article
Abnormal phase-amplitude coupling between β and broadband-γ activities has been identified in recordings from the cortex or scalp of patients with Parkinson’s disease. While enhanced phase-amplitude coupling has been proposed as a biomarker of Parkinson’s disease, the neuronal mechanisms underlying the abnormal coupling and its relationship to moto...
Article
Full-text available
The paper presents an experimental study where the distinctness of grey and white matter of an in situ postmortem porcine brain by impedance measurements is investigated. Experimental conditions that would allow to conduct the same experiment on in vivo human brain tissue are replicated.
Preprint
Full-text available
The feasibility of non-invasive axonal diameter quantification with diffusion MRI is a strongly debated topic due to the neuroscientific potential of such information and its relevance for the axonal signal transmission speed. It has been shown that under ideal conditions, the minimal diameter producing detectable signal decay is bigger than most h...
Poster
Full-text available
The precise cortical location underlying the physiological and behavioral TMS effects are still only coarsely known. So far, mapping strategies rely on center of gravity approaches and therefore localize the stimulated cortical site only approximately and indirectly. Such mappings have practical clinical relevance, for example in the context of pre...
Preprint
Full-text available
The neocortex is organized around layered microcircuits consisting of a variety of excitatory and inhibitory neuronal types which perform rate-and oscillation based computations. Using modeling, we show that both superficial and deep layers of the primary mouse visual cortex implement two ultrasensitive and bistable switches built on mutual inhibit...
Article
Bursting plays an important role in neural communication. At the population level, macroscopic bursting has been identified in populations of neurons that do not express intrinsic bursting mechanisms. For the analysis of such phase transitions, mean-field descriptions of macroscopic bursting behavior are a valuable tool. In this article, we derive...
Preprint
Full-text available
The paper presents an experimental study where the distinctness of grey and white matter of an in situ postmortem porcine brain by impedance measurements is investigated. Experimental conditions that would allow to conduct the same experiment on in vivo human brain tissue are replicated. https://doi.org/10.1515/cdbme-2019-XXXX
Preprint
Full-text available
Axonal connections are widely regarded as faithful transmitters of neuronal signals with fixed delays. The reasoning behind this is that extra-cellular potentials caused by spikes travelling along axons are too small to have an effect on other axons. Here we devise a computational framework that allows us to study the effect of extracellular potent...
Article
Full-text available
Despite the widespread use of transcranial magnetic stimulation (TMS), the precise cortical locations underlying the resulting physiological and behavioral effects are still only coarsely known. To date, mapping strategies have relied on projection approaches (often termed "center of gravity" approaches) or maximum electric field value evaluation,...
Article
Full-text available
We present a novel Python package for the uncertainty and sensitivity analysis of computational models. The mathematical background is based on the non-intrusive generalized polynomial chaos method allowing one to treat the investigated models as black box systems, without interfering with their legacy code. Pygpc is optimized to analyze models wit...
Article
Full-text available
In neuroscience, computational modeling has become an important source of insight into brain states and dynamics. A basic requirement for computational modeling studies is the availability of efficient software for setting up models and performing numerical simulations. While many such tools exist for different families of neural models, there is a...
Article
Full-text available
Neural responses to sudden changes can be observed in many parts of the sensory pathways at different organizational levels. For example, deviants that violate regularity at various levels of abstraction can be observed as simple On/Off responses of individual neurons or as cumulative responses of neural populations. The cortical deviance-related r...
Article
Full-text available
With the advent of advanced MRI techniques it has become possible to study axonal white matter non-invasively and in great detail. Measuring the various parameters of the long-range connections of the brain opens up the possibility to build and refine detailed models of large-scale neuronal activity. One particular challenge is to find a mathematic...
Preprint
Full-text available
In this Letter, we derive mean-field descriptions of populations of spiking neurons in which collective bursting behavior arises via short-term adaptation mechanisms. Specifically, we consider synaptic depression and spike-frequency adaptation in networks of quadratic integrate-and-fire neurons. We characterize the emerging bursting behavior using...
Poster
We proposed a method to determine the cortical site of stimulation by TMS by combining behavioral data with electric field simulations: the congruence factor. Here we verify its robustness against uncertain model parameters and measurement uncertainties with the adaptive generalized polynomial chaos (gPC) method. Discussion The congruence factor q...
Article
Full-text available
The concept of connectionism states that higher cognitive functions emerge from the interaction of many simple elements. Accordingly, research on canonical microcircuits conceptualizes findings on fundamental neuroanatomical circuits as well as recurrent organizational principles of the cerebral cortex and examines the link between architectures an...
Preprint
Full-text available
In neuroscience, computational modeling has become an important source of insight into brain states and dynamics. A basic requirement for computational modeling studies is the availability of efficient software for setting up models and performing numerical simulations. While many such tools exist for different families of neural models, there is a...
Preprint
Full-text available
With the advent of advanced MRI techniques it has become possible to study axonal white matter non-invasively and in great detail. Measuring the various parameters of the long-range connections of the brain opens up the possibility to build and refine detailed models of large-scale neuronal activity. One particular challenge is to find a mathematic...
Preprint
Full-text available
Despite the widespread use of transcranial magnetic stimulation (TMS), its precise cortical location underlying the physiological and behavioral stimulation effects are still only coarsely known. So far, mapping strategies that systematically measure TMS effects rely on center of gravity approaches and therefore localize the stimulated cortical sit...
Preprint
Full-text available
Neural responses to sudden changes can be observed in many parts of the sensory pathways at different organizational levels. For example, deviants that violate regularity at various levels of abstraction can be observed as simple On/Off responses of individual neurons or as cumulative responses of neural populations. The cortical deviance-related r...
Article
Uncertainty surrounding ohmic tissue conductivity impedes accurate calculation of the electric fields generated by non-invasive brain stimulation. We present an efficient and generic technique for uncertainty and sensitivity analyses, which quantifies the reliability of field estimates and identifies the most influential parameters. For this purpos...
Poster
Full-text available
Transcranial magnetic stimulation (TMS) allows for non-invasive electromagnetic stimulation of the cortex. However, its exact neurophysiological mechanisms remain elusive, leading to considerable variation in observed effects [1]. Depending on stimulation intensity and target, the stimulation can directly lead to observable effects, such as motor r...
Conference Paper
Full-text available
Die Rekonstruktion von Gehirnaktivität aus EEG/MEG-Daten erfordert die Lösung des bioelektromagnetischen inversen Problems. Ein Lösungsansatz besteht in der Verwendung verteilter Quellenmodelle, wobei Zusatzannahmen über die Beschaffenheit der Lösung getroffen werden müssen. Dabei kann auch aus Zusatzwissen abgeleitete Information integriert werden...
Article
One of the major challenges in systems neuroscience is to identify brain networks and unravel their significance for brain function -this has led to the concept of the 'connectome'. Connectomes are currently extensively studied in large-scale international efforts at multiple scales, and follow different definitions with respect to their connection...
Article
Full-text available
Major cognitive functions such as language, memory, and decision-making are thought to rely on distributed networks of a large number of basic elements, called canonical microcircuits. In this theoretical study we propose a novel canonical microcircuit model and find that it supports two basic computational operations: a gating mechanism and workin...
Data
Deactivation diagram for brief input to the IIN. Sufficiently long and strong impulses to the IIN (blue area) are able to deactivate the system, i.e. transfer the system from the active to the inactive state. (TIF)
Data
Phase-dependency between the system’s intrinsic oscillation and stimulus switch off time. The diagram shows a collection of system responses to stimuli of constant intensity (100s-1) and stimulus durations ranging between 600-750ms, where the stimulus offset times are marked by vertical lines. Blue lines denote stimuli responses, for which the syst...
Data
Dynamic function map for the indirect excitatory feedback architecture (see Fig 1B). A) Collection of characteristic fingerprints for varying excitatory (He) and inhibitory (Hi) synaptic gains. Colors code the observed response behaviors: nonresponsive (bright green, anthracite and cyan regions), transfer (grey regions), and memory (orange and rose...
Data
Increasing recurrent inhibitory self-feedback in the two-population model. A) The two parameter bifurcation plot tracks the occurring bifurcations along pext, when recurrent inhibitory self-feedback NII is increased (i.e., b2 is set to zero, see Fig 1D). The network balance was held constant at values He = 3.25mV and Hi = 22mV. B-E) The single para...
Data
Gradual mapping of two excitatory populations into a single one by introducing self-feedback NPP. (PDF)
Data
Dynamic function map for the direct excitatory feedback architecture (see Fig 1C). A) Collection of characteristic fingerprints for varying excitatory (He) and inhibitory (Hi) synaptic gains. Colors code the observed response behaviors: nonresponsive (bright green and anthracite), transfer (grey), and memory (orange). The variety of observed behavi...
Data
Dynamic function map for the two-population model with disinhibition (see Fig 1D). A) Collection of characteristic fingerprints for varying excitatory (He) and inhibitory (Hi) synaptic gains. Color-coded are the observed response behaviors: nonresponsive (bright green and anthracite), transfer (grey), and memory (orange). The variety of observed be...