Universität zu Köln

Hommelsen, Maximilian ORCID: 0000-0003-1972-0465 (2021). Inducing and detecting neuroplasticity: insights from TMS-EEG and RS-EEG. PhD thesis, Universität zu Köln.

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Abstract

Damage to the brain, such as stroke, can lead to severe cognitive and motor disabilities in the affected individuals. Neuroplasticity refers to the intrinsic capacities of the brain to reorganize cortical networks at different spatial and temporal scales, potentially resulting in spontaneous recovery of function after such damage. A better understanding about the measurement and the support of those neuroplastic processes is an important prerequisite to improve therapeutic interventions and ultimately the outcome of the recovery process. This thesis comprises the results of two studies that investigated the ability to induce neuroplasticity using repetitive transcranial magnetic stimulation (TMS) and the ability to measure neuroplasticity using a combination of TMS and electroencephalography (EEG) or resting state (RS)-EEG measurements in cohorts of young and healthy individuals. The first study utilized continuous theta burst stimulation (cTBS) to induce neuroplasticity targeting the primary motor cortex. After-effects on cortical and corticospinal excitability were quantified in terms of TMS-evoked potentials (TEP) and motor-evoked potentials. The study demonstrated that cTBS-induced neuroplasticity leads to significant local and remote changes in cortical excitability that were measurable with TMS-EEG. The modulation of the N45 peak of the TEP suggests that the neuroplastic effects of cTBS are mediated by changes in gamma-aminobutyric acid (GABA)A-mediated cortical inhibition. The second study investigated the suitability of RS-EEG for individualized longitudinal tracking of neuroplastic processes. In this scenario, it is important to distinguish whether observed changes in activity between measurements are attributable to incidental variations in cognitive state or truly related to processes of neuroplastic reorganization. A classification algorithm was adopted to extract individual-specific signatures from EEG oscillations at rest. These signatures were very robust across multiple days and detectable across different cognitive states, indicating a close relationship to the underlying neurophysiology. Using these individual activity pattern, it was possible to distinguish inter-day variations in cognitive state from simulated changes in the neurophysiological organization of the brain with very high accuracy. The current thesis therefore provides important support for the usability of TMS-EEG and RS-EEG as methodological approaches to measure neuroplasticity within healthy and young individuals. Furthermore, cTBS may be used as a strategy to interact with abnormally elevated or reduced levels of GABAA-mediated cortical inhibition. Further studies are required to validate the significance of the current findings and to test whether they can be translated into clinical practice, especially into the realms of stroke recovery.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Hommelsen, Maximilian max.hommelsen@gmx.de orcid.org/0000-0003-1972-0465 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-541633
Date:	3 December 2021
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Biology > Zoologisches Institut
Subjects:	Medical sciences Medicine
Uncontrolled Keywords:	Keywords Language EEG, Resting State, TMS, Neuroplasticity UNSPECIFIED
Date of oral exam:	27 October 2021
Referee:	Name Academic Title Daun, Silvia Prof. Nawrot, Martin Prof.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/54163