Project Summary Advances in brain mapping including the development of functional magnetic resonance imaging (fMRI) have increased our understanding of how the brain is organized to support neurologic functioning and what alterations in brain function are associated with numerous neurological and psychological illnesses. Particularly relevant for clinical applications, fMRI carries a clinical billing code reflecting its utility in presurgical planning for brain surgery. Due to its dependence on blood flow changes, BOLD fMRI suffers from both false negative and false positive results. To overcome some of the limitations of BOLD fMRI, we propose to investigate the feasibility of applying a completely novel MRI technique, functional magnetic resonance elastography (fMRE), for mapping human brain function. The fMRE technique does not depend on a neurovascular response, instead, it measures local mechanical changes in tissue resulting from a change in neuronal function. Our data has shown that fMRE can reveal neural responses at short timescales that cannot be due to the BOLD response. We hypothesize that fMRE is tightly coupled to primary neuronal activity, and hence will not be affected by the problems associated with BOLD fMRI. In this project, we propose to investigate the ability of fMRE to map sensorimotor function for presurgical brain mapping. We propose to compare and contrast fMRE and BOLD fMRI activations using sensorimotor tasks in individual subjects. In Aim 1, we will determine the similarities and differences between the fMRE and fMRI response to sensorimotor stimuli in healthy subjects, and investigate the feasibility of measuring neuromechanical responses which are independent from neurovascular response by varying the stimulus switching speed. In Aim 2, we will investigate fMRE in brain tumor patients to test the hypothesis that fMRE will not be affected by the problems seen in BOLD fMRI, and validate the activated regions against clinical gold-standard intra-operative brain mapping. This proposed innovative, high-risk, high-reward exploratory research will establish feasibility, reliability, and validity of fMRE for sensorimotor mapping. We believe that fMRE will develop into a novel transformative brain mapping technique with high temporal resolution and a broad range of neuroscience and clinical applications.