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February 2017
Our new paper is online! "Neural correlates of lexical decisions in Parkinson's Disease revealed with multivariate extraction of cortico-subthalamic interactions" Hohlefeld et al. (2017), Clinical Neurophysiology. |
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First evidence for the involvement of deep brain structures in aspects of lexical processing, here lexical accuracy: the stronger cortico-subthalamic neural synchronization, the more accurate were lexical decisions across patients with Parkinson's disease. The results might have implications for understanding neural circuits underlying language production and, possibly, speech deficits in Parkinsonian patients.
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November 2016
International Deep Brain Stimulation Symposium (Berlin, Germany) Poster: "Is it a word or pseudo word? Optimized extraction of cortico-subthalamic interactions as biomarker of lexical decisions in Parkinsonian patients" file for private use only
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March 2016b
2nd International Conference on Deep Brain Stimulation (Düsseldorf, Germany) Poster: "Cortico-subthalamic neural interactions: relation to cognitive task performance and evidence for a novel interaction mode across multiple time scales in patients with Parkinson’s disease" file for private use only
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Accuracy in lexical decisions relates to communication between human cortex
and the basal ganglia. |
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April 2015
Our new paper is online! Correlation between cortical and subcortical neural dynamics on multiple time scales in Parkinson's disease. Hohlefeld et al. (Neuroscience, 2015). We demonstrated a novel relation between cortical (EEG) and subcortical (basal ganglia LFP) neural dynamics, termed "multiscale interactions": long-range temporal dynamics (up to 20 sec) in cortical alpha oscillations (8-13 Hz) correlate with short-term phase synchronization (millisecond range) in subcortical beta oscillations (10-20 Hz). Our finding contributes to further understanding the role of long-distance neural interactions in Parkinson's disease. |
Our results suggest a novel communication mode between cortex and subcortical regions: neural interactions across multiple time scales and frequency bands.
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February 2015
2nd International Symposium of the Clinical Research Group 219 (Köln, Germany) Poster: "Multiscale interactions - a novel relation between cortical and subthalamic neural dynamics in patients with Parkinson's disease" file for private use only
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September 2014
Our new paper is online! Interhemispheric functional interactions between the subthalamic nuclei of patients with Parkinson's disease. Hohlefeld et al. (European Journal of Neuroscience, 2014). We demonstrated for the first time genuine coherence (i.e., no volume conduction!) between both subthalamic nuclei in deep brain recordings. And we were excited to show also its clinical relevance: across patients, interhemispheric coherence was modulated by dopaminergic medication, and was correlated with motor symptoms. |
Both brain hemispheres synchronize in Parkinsonian patients - demonstrated with coherency methods (iCOH) that reject "false" neural interactions due to volume conduction artifacts.
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August 2014
It was my great pleasure to visit Prof. Scott Kelso's Human Brain and Behavior Lab (Center for Complex Systems and Brain Sciences, Florida Atlantic University) for a week, and to give the guest lecture: "To move and not to move – neural variability and quasi-movements in the Parkinsonian and healthy motor system“ [abstract] [video; thanks @Craig Nordham] Acknowledgements: travel funding by DAAD. |
Quasi-movements, the "subquantum" of action - discussing a dynamical systems approach.
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June 2014
Human Brain Mapping conference (Hamburg, Germany) Poster: "Beyond volume conduction: toward genuine functional connectivity between bilateral basal ganglia" file for private use only.
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Complex neural synchronization pathways between the two hemispheres of the human brain.
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April 2014
It was my great pleasure to visit Prof. Mark Hallett's lab (Neurology, Human Motor Control Section) at the National Institute of Health. I was giving the guest lecture: "To move or not no move – neural correlates in the Parkinsonian and healthy motor system". |
Sunny morning at the NIH Clinical Center
before giving my talk. |
