Human Brain Mapping Using Structural and Functional Magnetic Resonance Imaging and Transcranial Magnetic Stimulation

Modern brain research methods such as magnetic resonance imaging (MRI), functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) have provided essential information of the structure and function of the human brain. However, to be practical in clinics, they need to be optimized for the clinical environment and to be easy to use and robust. At the same time, the research community would benefit from the combined use of different modalities since it would provide a wider perspective and more comprehensive understanding of the issue. The aim of this study is to develop analysis methods of TMS and functional and structural MRI to study the brain areas related to motor functions and speech and language. The findings demonstrate the advantages of combining different methods and modalities in brain research. For studying the function of the motor areas, a methodology to present the information provided by TMS at the group level is proposed. In this thesis, navigated TMS is used to define the normal variation in the cortical representation areas of thenar and anterior tibial muscles in a healthy population. To obtain information about the complementary brain areas for motor function, TMS is combined with structural MRI analysis of cortical thickness. This provides detailed information of the progression of Alzheimer’s disease. For studying areas involved in speech and language, a suitable fMRI task battery to define the hemispheric language dominance is developed. Finally, for brain research in general, a novel method to study functional connectivity is developed based on the principal component analysis (PCA). The method enables both single-trial level and general task-level analysis of the functional connectivity. National Library of Medicine Classification: WL 141.5.M2, WL 141.5.T7, WL 335, WN 185 Medical subject headings: Brain Mapping/methods; Neuroimaging/methods; Magnetic Resonance Imaging; Transcranial Magnetic Stimulation; Cerebral Cortex; Motor Cortex; Speech; Language; Dominance, Cerebral; Alzheimer’s Disease; Principal Component Analysis Yleinen suomalainen sanasto: aivotutkimus; aivot; aivokuori; kartoitus; kuvantaminen; magneettitutkimus; liike; puhe; kieli; Alzheimerin tauti