@article{PasosSteigerwaldReichetal.2019,
  author    = {Pasos, Uri E. Ramirez and Steigerwald, Frank and Reich, Martin M. and Matthies, Cordula and Volkmann, Jens and Reese, Ren{\´e}},
  title     = {Levodopa modulates functional connectivity in the upper beta band between bubthalamic nucleus and muscle activity in tonic and phasic motor activity patterns in Parkinson's disease},
  series = {Frontiers in Human Neuroscience},
  volume    = {13},
  journal   = {Frontiers in Human Neuroscience},
  number    = {223},
  doi       = {10.3389/fnhum.2019.00223},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-201540},
  year      = {2019},
  abstract  = {Introduction: Striatal dopamine depletion disrupts basal ganglia function and causes Parkinson's disease (PD). The pathophysiology of the dopamine-dependent relationship between basal ganglia signaling and motor control, however, is not fully understood. We obtained simultaneous recordings of local field potentials (LFPs) from the subthalamic nucleus (STN) and electromyograms (EMGs) in patients with PD to investigate the impact of dopaminergic state and movement on long-range beta functional connectivity between basal ganglia and lower motor neurons. Methods: Eight PD patients were investigated 3 months after implantation of a deep brain stimulation (DBS)-system capable of recording LFPs via chronically-implanted leads (Medtronic, ACTIVA PC+S®). We analyzed STN spectral power and its coherence with EMG in the context of two different movement paradigms (tonic wrist extension vs. alternating wrist extension and flexion) and the effect of levodopa (L-Dopa) intake using an unbiased data-driven approach to determine regions of interest (ROI). Results: Two ROIs capturing prominent coherence within a grand average coherogram were identified. A trend of a dopamine effect was observed for the first ROI (50-150 ms after movement start) with higher STN-EMG coherence in medicated patients. Concerning the second ROI (300-500 ms after movement start), an interaction effect of L-Dopa medication and movement task was observed with higher coherence in the isometric contraction task compared to alternating movements in the medication ON state, a pattern which was reversed in L-Dopa OFF. Discussion: L-Dopa medication may normalize functional connectivity between remote structures of the motor system with increased upper beta coherence reflecting a physiological restriction of the amount of information conveyed between remote structures. This may be necessary to maintain simple movements like isometric contraction. Our study adds dynamic properties to the complex interplay between STN spectral beta power and the nucleus' functional connectivity to remote structures of the motor system as a function of movement and dopaminergic state. This may help to identify markers of neuronal activity relevant for more individualized programming of DBS therapy.},
  language  = {en}
}
@article{CanessaPozziArnulfoetal.2016,
  author    = {Canessa, Andrea and Pozzi, Nicol{\`o} G. and Arnulfo, Gabriele and Brumberg, Joachim and Reich, Martin M. and Pezzoli, Gianni and Ghilardi, Maria F. and Matthies, Cordula and Steigerwald, Frank and Volkmann, Jens and Isaias, Ioannis U.},
  title     = {Striatal Dopaminergic Innervation Regulates Subthalamic Beta-Oscillations and Cortical-Subcortical Coupling during Movements: Preliminary Evidence in Subjects with Parkinson's Disease},
  series = {Frontiers in Human Neuroscience},
  volume    = {10},
  journal   = {Frontiers in Human Neuroscience},
  number    = {611},
  doi       = {10.3389/fnhum.2016.00611},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-164061},
  year      = {2016},
  abstract  = {Activation of the basal ganglia has been shown during the preparation and execution of movement. However, the functional interaction of cortical and subcortical brain areas during movement and the relative contribution of dopaminergic striatal innervation remains unclear. We recorded local field potential (LFP) activity from the subthalamic nucleus (STN) and high-density electroencephalography (EEG) signals in four patients with Parkinson's disease (PD) off dopaminergic medication during a multi-joint motor task performed with their dominant and non-dominant hand. Recordings were performed by means of a fully-implantable deep brain stimulation (DBS) device at 4 months after surgery. Three patients also performed a single-photon computed tomography (SPECT) with [123I]N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane (FP-CIT) to assess striatal dopaminergic innervation. Unilateral movement execution led to event-related desynchronization (ERD) followed by a rebound after movement termination event-related synchronization (ERS) of oscillatory beta activity in the STN and primary sensorimotor cortex of both hemispheres. Dopamine deficiency directly influenced movement-related beta-modulation, with greater beta-suppression in the most dopamine-depleted hemisphere for both ipsi- and contralateral hand movements. Cortical-subcortical, but not interhemispheric subcortical coherencies were modulated by movement and influenced by striatal dopaminergic innervation, being stronger in the most dopamine-depleted hemisphere. The data are consistent with a role of dopamine in shielding subcortical structures from an excessive cortical entrapment and cross-hemispheric coupling, thus allowing fine-tuning of movement.},
  language  = {en}
}