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Abstract:
Functional Magnetic Resonance Imaging (fMRI) is a very popular method in neurosciences to detect “brain activity” noninvasively in the living human brain. On a cellular level, brain activity can be defined as a communication between neurons via action potentials along interconnecting axons and synapses. Electrophysiology can directly measure these action potentials while magnetic resonance imaging is (currently) not able to detect these tiny potential changes (via induced magnetic fields). Instead, fMRI is based on an indirect mechanism, the so-called neurovascular coupling, that relates changes of hemodynamics such as blood oxygenation, volume and flow to neuronal activation. In this lecture I will describe several mechanisms of MR signal formation within a neurovascular network that leads to the so-called blood oxygenation level dependent (BOLD) effect, and which physiological and acquisition-related parameters influence this BOLD signal.
