NOVEL MULTI-MODALITY MRI AND TRANSCRANIAL MAGNETIC STIMULATION TO STUDY BRAIN

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Magnetic resonance imaging (MRI) provides high-resolution scans of the human brain and other organs where image contrast is based principally on regional differences in proton relaxation times. The sensitivity of magnetic resonance to various aspects of tissue physical chemistry led to the development of a functional MRI (fMRI) technique that can probe tissue physiology and pathology beyond the scope of simple anatomical imaging. The well-known blood oxygenation level-dependent (BOLD) method relies on the sensitivity of the effective T2 relaxation time to the oxidation state of hemoglobin iron, which in turn is sensitive to alterations in oxygen consumption rate. Changes in the BOLD signal following presentation of stimuli reflect changes in neuronal activation, and can therefore be used to map functional pathways in the brain. The assessment of the structural basis associated with the functional brain areas have been achieved combining BOLD contrast and diffusion tensor imaging (DTI) [1], which permits the visualization of the tracts or bundles of neuronal axons that connect different parts of the brain. Nevertheless, since these functional techniques reveal the brain networks involved in specific functions, they cannot alone prove that a specific area is essential for a particular function. The combination of fMRI and transcranial magnetic stimulation (TMS), which is non-invasive and painless, can transiently disrupt activity in focal brain regions [2]. This combination was the initial trial to improve the acknowledgement about the contribution of specific areas in brain activity. Therefore, in this project we propose to develop a revolutionary methodology integrating TMS, fMRI and DTI, using BNL's 4-T MR scanner, so as to provide the unique windows on brain function and connectivity.