@article{PozziBolzoniBiellaetal.2023,
  author    = {Pozzi, Nicol{\´o} Gabriele and Bolzoni, Francesco and Biella, Gabriele Eliseo Mario and Pezzoli, Gianni and Ip, Chi Wang and Volkmann, Jens and Cavallari, Paolo and Asan, Esther and Isaias, Ioannis Ugo},
  title     = {Brain noradrenergic innervation supports the development of Parkinson's tremor: a study in a reserpinized rat model},
  series = {Cells},
  volume    = {12},
  journal   = {Cells},
  number    = {21},
  issn      = {2073-4409},
  doi       = {10.3390/cells12212529},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-357721},
  year      = {2023},
  abstract  = {The pathophysiology of tremor in Parkinson's disease (PD) is evolving towards a complex alteration to monoaminergic innervation, and increasing evidence suggests a key role of the locus coeruleus noradrenergic system (LC-NA). However, the difficulties in imaging LC-NA in patients challenge its direct investigation. To this end, we studied the development of tremor in a reserpinized rat model of PD, with or without a selective lesioning of LC-NA innervation with the neurotoxin DSP-4. Eight male rats (Sprague Dawley) received DSP-4 (50 mg/kg) two weeks prior to reserpine injection (10 mg/kg) (DR-group), while seven male animals received only reserpine treatment (R-group). Tremor, rigidity, hypokinesia, postural flexion and postural immobility were scored before and after 20, 40, 60, 80, 120 and 180 min of reserpine injection. Tremor was assessed visually and with accelerometers. The injection of DSP-4 induced a severe reduction in LC-NA terminal axons (DR-group: 0.024 ± 0.01 vs. R-group: 0.27 ± 0.04 axons/um\(^2\), p < 0.001) and was associated with significantly less tremor, as compared to the R-group (peak tremor score, DR-group: 0.5 ± 0.8 vs. R-group: 1.6 ± 0.5; p < 0.01). Kinematic measurement confirmed the clinical data (tremor consistency (\% of tremor during 180 s recording), DR-group: 37.9 ± 35.8 vs. R-group: 69.3 ± 29.6; p < 0.05). Akinetic-rigid symptoms did not differ between the DR- and R-groups. Our results provide preliminary causal evidence for a critical role of LC-NA innervation in the development of PD tremor and foster the development of targeted therapies for PD patients.},
  language  = {en}
}
@phdthesis{Pozzi2020,
  author    = {Pozzi, Nicol{\´o} Gabriele},
  title     = {Parkinson's disease revisited: multiple circuitopathies},
  doi       = {10.25972/OPUS-21671},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-216715},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2020},
  abstract  = {Parkinson's disease (PD) is among the most common neurodegenerative conditions, and it is characterized by the progressive loss of dopaminergic neurons and a great variability in clinical expression. Despite several effective medications, it still causes disability as all patients show treatment-resistant symptoms and complications. A possible reason for this therapeutic-burden and great clinical variability lies in a probable misconception about its pathophysiology, one that focuses on neurodegeneration, while largely neglecting its functional consequences and the related compensatory changes. In this thesis, I expand on the hypothesis that some PD symptoms have a dysfunctional origin and reflect derangements of neural network dynamics, the means by which brain coordination supports any motor behaviour. In particular, I have investigated resting tremor and freezing of gait, two common symptoms with an enigmatic mechanism and suboptimal management. In the case of tremor, I predicted a pathological change in response to dopamine loss, which included the activation of noradrenergic (NA) neurons of the locus coeruleus (LC) projecting to the cerebellum. This compensatory LC activation that supports dopaminergic neurons might indeed come at the expense of tremor development. To assess the role of LC-NA in tremor development, I recorded tremor occurrence in the reserpinized rat model of PD, one of very few showing tremor, after selective lesioning (with the neurotoxin DSP-4) of the LC-NA terminal axons. DSP-4 induced a severe reduction of LC-NA terminal axons in the cerebellar cortex and this was associated with a significant reduction in tremor development. Unlike its development, tremor frequency and the akinetic rigid signs did not differ between the groups, thus suggesting a dopaminergic dependency. These findings suggest that the LC-NA innervation of the cerebellum has a critical role for PD tremor, possibly by exerting a network effect, which gates the cerebello-thalamic-cortical circuit into pathological oscillations upon a dopaminergic loss in the basal ganglia. In contrast, for the study of freezing of gait, I worked with human PD subjects and deep brain stimulation, a therapeutic neuromodulation device that in some prototypes also allows the recording of neural activity in freely-moving subjects. Gait freezing is a disabling PD symptom that suddenly impairs effective stepping, thus causing falls and disability. Also in this study, I hypothesized that the underlying pathophysiology may be represented by dysfunctional neural network dynamics that abruptly impair locomotor control by affecting the communication in the supraspinal locomotor network. To test this hypothesis, I investigated the coupling between the cortex and the subthalamic nucleus, two main nodes of the supraspinal locomotor network, in freely-moving subjects PD patients and also performed molecular brain imaging of striatal dopamine receptor density and kinematic measurements. I found that in PD patients, walking is associated with cortical-subthalamic stable coupling in a low-frequency band (i.e. θ-α rhythms). In contrast, these structures decoupled when gait freezing occurred in the brain hemisphere with less dopaminergic innervation. These findings suggest that freezing of gait is a "circuitopathy", with dysfunctional cortical-subcortical communication. Altogether the results of my experiments support the hypothesis that the pathophysiology of PD goes beyond neurodegenerative (loss-of-function) processes and that derangement of neural network dynamics coincides with some disabling PD symptoms, thus suggesting that PD can be interpreted as the combination of multiple circuitopathies.},
  subject      = {Parkinson-Krankheit},
  language  = {en}
}
@article{DelVecchioHanafiPozzietal.2023,
  author    = {Del Vecchio, Jasmin and Hanafi, Ibrahem and Pozzi, Nicol{\´o} Gabriele and Capetian, Philipp and Isaias, Ioannis U. and Haufe, Stefan and Palmisano, Chiara},
  title     = {Pallidal recordings in chronically implanted dystonic patients: mitigation of tremor-related artifacts},
  series = {Bioengineering},
  volume    = {10},
  journal   = {Bioengineering},
  number    = {4},
  issn      = {2306-5354},
  doi       = {10.3390/bioengineering10040476},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-313498},
  year      = {2023},
  abstract  = {Low-frequency oscillatory patterns of pallidal local field potentials (LFPs) have been proposed as a physiomarker for dystonia and hold the promise for personalized adaptive deep brain stimulation. Head tremor, a low-frequency involuntary rhythmic movement typical of cervical dystonia, may cause movement artifacts in LFP signals, compromising the reliability of low-frequency oscillations as biomarkers for adaptive neurostimulation. We investigated chronic pallidal LFPs with the Percept\(^{TM}\) PC (Medtronic PLC) device in eight subjects with dystonia (five with head tremors). We applied a multiple regression approach to pallidal LFPs in patients with head tremors using kinematic information measured with an inertial measurement unit (IMU) and an electromyographic signal (EMG). With IMU regression, we found tremor contamination in all subjects, whereas EMG regression identified it in only three out of five. IMU regression was also superior to EMG regression in removing tremor-related artifacts and resulted in a significant power reduction, especially in the theta-alpha band. Pallido-muscular coherence was affected by a head tremor and disappeared after IMU regression. Our results show that the Percept PC can record low-frequency oscillations but also reveal spectral contamination due to movement artifacts. IMU regression can identify such artifact contamination and be a suitable tool for its removal.},
  language  = {en}
}