Modulation Of Neuroplasticity In Humans By Advanced Stimulation Protocols And Neuromodulators

by Giorgi Batsikadze
Cumulative thesis
Date of Examination:2014-02-27
Date of issue:2014-04-09
Advisor:Prof. Dr. Michael Nitsche
Referee:Prof. Dr. Michael Nitsche
Referee:Prof. Dr. Uwe Mattler
Persistent Address: http://dx.doi.org/10.53846/goediss-4448

 

 

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Abstract

English

Neuroplasticity is a feature of the human brain to dynamically reorganize itself structurally as well as functionally in response to changes of the environment, behavior or brain injury. It can be accomplished via adding, removing, strengthening or weakening of synaptic connections as well as neurogenesis (Pascual-Leone et al., 2005, Pascual-Leone et al., 2011). Besides being one of the most important physiological mechanisms of learning, memory and other cognitive processes, pathologically altered neuroplasticity can cause neuropsychiatric diseases. The discovery and development of non-invasive brain stimulation techniques in the last decades has given researchers the opportunity to study neuroplasticity in humans. Transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS) and paired associative stimulation (PAS) are widely used techniques for non-invasively inducing and monitoring these processes in the human brain (Nitsche and Paulus, 2000, Stefan et al., 2000, Nitsche et al., 2008, Ziemann et al., 2008).   The present work is divided into two parts: first, the deeper exploration of mechanisms influencing brain plasticity using modified brain stimulation protocols and the second part, representing the impact of two major neuromodulators (serotonin and nicotine) on non-invasive brain stimulation-induced neuroplasticity. Several studies have previously demonstrated the impact of different neuromodulators on different types of plasticity in humans (Kuo et al., 2007, Kuo et al., 2008, Monte-Silva et al., 2009, Nitsche et al., 2009, Monte-Silva et al., 2010b, Thirugnanasambandam et al., 2012). In this thesis we aimed to study the impact of serotonin on synapse-specific focal plasticity induced by PAS and the dose-dependent effect of alpha-4-beta-2-nicotinic receptor activation on plasticity. The first chapter of this thesis will introduce basic information about neuroplasticity, neuromodulatory systems and techniques used in the studies presented in the second chapter. The last chapter will summarize the findings of the presented studies and offer an outlook and possible future research directions in the field.
Keywords: Transcranial Magnetic Stimulation; Transcranial Direct Current Stimulation; Paired Associative Stimulation; Varenicline; Nicotine; Neuroplasticity; Serotonin
 
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