Dokument: Neural oscillations underlying bicycling and walking

Titel:Neural oscillations underlying bicycling and walking
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URN (NBN):urn:nbn:de:hbz:061-20170322-095800-5
Dokumententyp:Wissenschaftliche Abschlussarbeiten » Dissertation
Autor: Storzer, Lena [Autor]
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Dateien vom 20.03.2017 / geändert 20.03.2017
Beitragende:Prof. Dr. Schnitzler, Alfons [Betreuer/Doktorvater]
Prof. Dr. Kalenscher, Tobias [Betreuer/Doktorvater]
Dewey Dezimal-Klassifikation:100 Philosophie und Psychologie » 150 Psychologie
Beschreibung:Bicycling and walking are two highly automated movements based on oscillatory activity in a distributed network comprising cortical and subcortical brain regions, spinal cord, and muscles. Alterations in the communication between these regions are observed in Parkinson’s disease (PD), a neurodegenerative disorder associated with pathological synchronization of oscillatory activity in the basal ganglia (BG). Consequently, gait impairments are a hallmark of PD. These are even more pronounced in PD patients suffering from freezing of gait (FOG), a puzzling phenomenon characterized by the sudden inability of forward progression. Although accumulating evidence suggests FOG to be associated with deficient movement automaticity, executive dysfunctions, and altered communication between cortical and subcortical regions, the exact underlying mechanism remains elusive so far. As bicycling ability is surprisingly retained in this patient population, comparing neural control of bicycling and walking offers a unique starting point for understanding the complex pathophysiology of FOG. Importantly, bicycling was also shown to be effective ameliorating PD symptoms, raising the question about its effect on brain activity.

This thesis contrasted modulation of neural oscillations by bicycling and walking in healthy subjects and PD patients in order to provide insight into both cortical and subcortical control of movement. Its ambition was to contribute to the understanding of the paradoxical bicycling capacity in patients with FOG, thereby revealing oscillatory signatures related to freezing susceptibility.

Two studies were performed based on the same experimental paradigm including initiation, execution, and termination of bicycling on a stationary bicycle as well as walking. Brain activity was concurrently recorded together with electromyography of the leg muscles and movement parameters including the knee angle and the pedal position.

Since not much is known about how bicycling differs from walking with respect to motor cortex activity, study 1 acquired electroencephalography in healthy participants to scrutinize modulation of alpha (8-12 Hz) and beta (13-35 Hz) rhythms that are known to be crucial for movement control. Interestingly, bicycling and walking were found to be accompanied by different oscillatory dynamics. Bicycling resulted in stronger sustained modulations of high beta band (23-35 Hz) activity but weaker alpha band activity relative to walking. At the same time, walking was characterized by stronger power modulations in the 24-40 Hz range as a function of the movement cycle. Apart from identifying frequency specific aspects of cortical motor control, these results suggest that bicycling involves stronger overall cortical activation while walking demands more cortical monitoring of ongoing movement.

Study 2 aimed at characterizing modulation of oscillatory activity in the BG of PD patients by recording local field potentials from electrodes implanted in the subthalamic nucleus (STN) for deep brain stimulation (DBS). Especially synchronization in the beta band was scrutinized as this is closely associated with the pathophysiology of PD. Study 2 revealed stronger STN beta power suppression during bicycling relative to walking. Crucially, patients with FOG showed an abnormal ~18 Hz oscillation during walking that was alleviated in bicycling. This suggests synchronization at ~18 Hz as an oscillatory signature for freezing susceptibility with freezing episodes being the consequence of a movement-inhibiting signal in a subcortical network.

The presented studies elucidate functional differences in the motor network subserving bicycling and walking, providing a key piece of the mechanism explaining how bicycling ability can remain preserved in patients with FOG. Results highlight the pivotal role of different specific beta rhythms in this context. Bicycling was accompanied by stronger beta power suppression in the striato-thalamo-cortical network, likely arising from its more continuous nature entailing low computational load on the motor system. Walking, on the other hand, is computationally more demanding and thus susceptible to excessive synchronization in the BG. This might finally result in ‘overloading’ the network involved in locomotion. This thesis thus provides important groundwork for future research clarifying the mechanism behind FOG. It may enlarge the therapeutic options for treating PD symptoms by including new DBS stimulation strategies and cycling protocols.
Fachbereich / Einrichtung:Medizinische Fakultät » Institute » Institut für Medizinische Psychologie
Dokument erstellt am:22.03.2017
Dateien geändert am:22.03.2017
Promotionsantrag am:02.11.2016
Datum der Promotion:09.02.2017
Status: Gast