Lecture04_PreprocessIII&IV_SpatialNormalization_PhysiologicArtifact

Lecture04_PreprocessIII&IV_SpatialNormalization_PhysiologicArtifact

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1 This Time • Reslice example… • Spatial Normalization • Noise in fMRI • Methods for estimating and correcting for physiologic noise • SPM Example Spatial Normalization: Remind ourselves what a typical functional image volume looks like: Realignment Realignment fMRI time -series series Slice Slice order order ‘Unwarp Unwarp Slice timing Slice timing Reorient fMRI Data analysis fMRI Data analysis fMRI Data analysis Realignment fMRI time -series series Normalisation Template Slice Slice order order ‘Unwarp Unwarp Slice timing Slice timing Reorient Talairach Coordinate System Talairach Coordinate System to provide mechanism for comparing data across different labs/studies Talairach coordinate system (space) • Atlas provided by Talairach and Tournoux – Based on a French woman’s brain – Center (0,0,0 is on the anterior commissure) – Line passes through the Anterior commissure – Posterior commissure line (a.k.a., AC-PC line)
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2 Talairach Coordinate System Note: That’s TalAIRach, not TAILarach! Individual brains are different shapes and sizes… How can we compare or average brains? Talairach & Tournoux, 1988 • squish or stretch brain into “shoe box” • extract 3D coordinate (x, y, z) for each activation focus Rotate brain into ACPC plane Find posterior commisure (PC) Find anterior commisure (AC) ACPC line = horizontal axis Corpus Cal osum Fornix Pineal Body “bent asparagus” Note: official Tal sez use top of AC and bottom of PC Source: Duvernoy, 1999 Squish or stretch brain to fit in “shoebox” of Tal system Deform brain into Talairach space y AC=0 y>0 y<0 ACPC=0 y>0 y<0 z x Extract 3 coordinates Mark 8 points in the brain: • anterior commisure • posterior commisure • front • back •top • bottom (of temporal lobe) •left • right Talairach Atlas
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3 Talairach Pros and Cons Advantages • widespread system • allows averaging of fMRI data between subjects • allows researchers to compare activation foci • easy to use Disadvantages • based on the squished brain of an elderly alcoholic woman (how representative is that?!) • not appropriate for all brains (e.g., Japanese brains don’t fit well) • activation foci can vary considerably – other landmarks like sulci may be more reliable •Ignores left/right differences Left is what?!!! Neurologic (i.e. sensible) convention • left is left, right is right LR Radiologic (i.e. stupid) convention • left is right, right is left RL Note: Make sure you know what your magnet and software are doing before publishing left/right info!
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This note was uploaded on 02/10/2010 for the course TBE 2300 taught by Professor Cudeback during the Spring '10 term at Webber.

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Lecture04_PreprocessIII&amp;IV_SpatialNormalization_PhysiologicArtifact

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