[医学]1A_Louain_fMRI_Introduction_No2008.pptVIP

Introduction to Functional MRI MRI vs. fMRI Brain Imaging: Anatomy The First “Brain Imaging Experiment” The Rise of fMRI fMRI Activation PET and fMRI Activation fMRI Setup Category-Specific Visual Areas Lateral Occipital (LO) object-selective objects (faces scenes) objects scrambled images A Simple Experiment: LO Localizer fMRI Experiment Stages: Prep fMRI Experiment Stages: Anatomicals Slice Terminology fMRI Experiment Stages: Functionals Anatomic Slices Corresponding to Functional Slices Time Courses Activation Statistics Statistical Maps Time Courses Stats on Anatomical 2D ? 3D Design Jargon: Runs Design Jargon: Paradigm Recipe for MRI Necessary Equipment The Big Magnet Susceptibility Artifacts The Benefit of Susceptibility Deoxygenated Blood ? Signal Loss Oxygenated blood? No signal loss… Hemoglobin BOLD Time Course Stimulus to BOLD Neural Networks Post-Synaptic Potentials The inputs to a neuron (post-synaptic potentials) increase (excitatory PSPs) or decrease (inhibitory PSPs) the membrane voltage If the summed PSPs at the axon hillock push the voltage above the threshold, the neuron will fire an action potential Even Simple Circuits Aren’t Simple Will BOLD activation from the blue voxel reflect: output of the black neuron (action potentials)? excitatory input (green synapses)? inhibitory input (red synapses)? inputs from the same layer (which constitute ~80% of synapses)? feedforward projections (from lower-tier areas)? feedback projections (from higher-tier areas)? BOLD Correlations Local Field Potentials (LFP) reflect post-synaptic potentials similar to what EEG (ERPs) and MEG measure Multi-Unit Activity (MUA) reflects action potentials similar to what most electrophysiology measures Logothetis et al. (2001) combined BOLD fMRI and electrophysiological recordings found that BOLD activity is more closely related to LFPs than MUA Comparing Electrophysiolgy and BOLD fMRI Measures the Population Activity population activity depends on how activ