HUMAN BRAIN
IMAGING:
principles and methodology
Samenvatting
Rosanne
,Inhoud
1 Introduction ............................................................................................................................................................... 5
1.1 Little overview .................................................................................................................................................. 5
1.2 Introduction ....................................................................................................................................................... 5
1.2.1 Brain enthusiasm: The relevance of distinguishing fact from fiction ....................................................... 5
1.3 The basis of neural signals ................................................................................................................................ 7
1.3.1 Information Transfer in Neurons .............................................................................................................. 7
1.3.2 Signal processing ...................................................................................................................................... 8
Some concepts....................................................................................................................................................... 8
1.3.3 Molecular and hemodynamic signals ...................................................................................................... 10
Energy consumption ........................................................................................................................................... 10
Clustering ............................................................................................................................................................ 10
1.3.4 A short overview of methods in human neuroscience ............................................................................ 11
Measuring brain structure ................................................................................................................................... 11
Measuring hemodynamics .................................................................................................................................. 12
Measuring electrophysiological activity ............................................................................................................. 12
Example .............................................................................................................................................................. 12
2 Structural neuroimaging (ch2); the physics behind MRI ........................................................................................ 13
2.1 The effect of the magnetic fields on the human body ..................................................................................... 13
2.1.1 Magnetic field effect ............................................................................................................................... 13
2.1.2 Gradients ................................................................................................................................................. 14
Gradients of field strength................................................................................................................................... 14
A. Slice selection gradient ........................................................................................................................... 14
B. Phase encoding gradient ......................................................................................................................... 15
C. Frequency encoding gradient ................................................................................................................. 15
Pulse sequences ................................................................................................................................................... 15
Creating a spatial image from the signal ............................................................................................................. 16
2.1.3 Fourier analysis ....................................................................................................................................... 16
2.2 How do these physical principles give rise to an image with anatomical structure? ...................................... 17
2.2.1 T1 recover and T2 decay ......................................................................................................................... 18
2.2.2 Weighted contrasts .................................................................................................................................. 18
2.3 The hardware of scanner ................................................................................................................................. 19
2.4 Parameters which are chosen by the user ........................................................................................................ 19
3 Structural neuroimaging (ch3) ................................................................................................................................ 19
3.1 Structural T1-weighted MRI ........................................................................................................................... 19
3.1.1 Normalization.......................................................................................................................................... 19
Volume-based normalization .............................................................................................................................. 20
Segmentation-based normalization ..................................................................................................................... 20
Surface-based normalization ............................................................................................................................... 20
3.1.2 Cortical surface and voxels ..................................................................................................................... 21
1
, 3.1.3 Morphometry & VLSM .......................................................................................................................... 21
3.2 Different tensor imaging (DTI) ....................................................................................................................... 22
3.2.1 Diffusion-weighted imaging (DWI) ........................................................................................................ 22
3.2.2 Data analysis ........................................................................................................................................... 23
3.2.3 Interpretation ........................................................................................................................................... 24
4 Hemodynamic neuroimaging .................................................................................................................................. 25
4.1 Introduction ..................................................................................................................................................... 25
4.2 Hemodynamics and its relationship to neural activity .................................................................................... 25
4.2.1 3 components of HRF & measurement ................................................................................................... 26
4.2.2 Neural activity and HR ........................................................................................................................... 26
4.3 Functional magnetic resonance imaging (fMRI) ............................................................................................ 27
4.3.1 GE EPI .................................................................................................................................................... 28
4.3.2 Relavence of fMRI .................................................................................................................................. 29
4.4 Positron Emission Tomography (PET) ........................................................................................................... 29
4.4.1 PET to measure neural activity ............................................................................................................... 29
4.4.2 PET versus fMRI .................................................................................................................................... 30
4.4.3 Unique contribution of PET .................................................................................................................... 30
4.5 Functional Near InfraRed Spectroscopy (fNIRS) .......................................................................................... 30
4.5.1 (Dis)advantages of fNIRS compared to fMRI ........................................................................................ 31
4.6 A comparison of research with fMRI, PET, and fNIRS ................................................................................. 31
5 Designing a hemodynamic imaging experiment ..................................................................................................... 32
5.1 Think before you start an experiment ............................................................................................................. 32
5.2 Which conditions to include: The subtraction method ................................................................................... 32
5.3 How to present the conditions ......................................................................................................................... 33
5.3.1 Block design............................................................................................................................................ 33
5.3.2 The event-related design ......................................................................................................................... 34
5.4 The baseline or rest condition ......................................................................................................................... 35
5.5 Task and stimuli in the scanner ....................................................................................................................... 36
6 Hemodynamic imaging (Ch 6): image processing .................................................................................................. 37
6.1 Role of image pre-processing ......................................................................................................................... 37
6.2 Properties of the images .................................................................................................................................. 37
6.2.1 4D fMRI data .......................................................................................................................................... 38
6.2.2 Preprocessing: the steps .......................................................................................................................... 38
Step 0: Quality control ........................................................................................................................................ 38
6.2.3 Step 1: slice timing .................................................................................................................................. 39
6.2.4 Step 2: Motion correction ....................................................................................................................... 39
6.2.5 Step 3: Co-registration ............................................................................................................................ 40
6.2.6 Step 4: Normalization ............................................................................................................................. 41
6.2.7 Step 5: spatial smoothing ........................................................................................................................ 41
7 Hemodyamic imaging (Ch7): basis statistical analyses ......................................................................................... 43
2
, 7.1 Statistical analyses: The general linear model ................................................................................................ 43
7.1.1 Simple linear regression .......................................................................................................................... 43
7.1.2 Multiple linear regression ....................................................................................................................... 43
7.1.3 GLM for fMRI ........................................................................................................................................ 44
Regressors of interest .......................................................................................................................................... 44
Clean your data & whitening .............................................................................................................................. 45
Efficiency of the design ...................................................................................................................................... 46
7.2 Determining significance and interpreting it................................................................................................... 47
7.2.1 Assumptions or assumptions ................................................................................................................... 47
7.2.2 Multiple comparisons .............................................................................................................................. 48
7.2.3 Second-level whole-brain analyses and ROI analysis............................................................................. 49
Whole brain ......................................................................................................................................................... 49
ROI ...................................................................................................................................................................... 49
7.2.4 Interference ............................................................................................................................................. 51
8 Hemodynamic Imaging (Ch 8): Advanced statistical analyses ............................................................................... 52
8.1 Functional connectivity ................................................................................................................................... 52
8.1.1 Designs and analyses .............................................................................................................................. 52
Caveats: time scale, correlation, subject motion ................................................................................................. 52
8.1.2 Modeling directional functional connectivity ......................................................................................... 54
8.1.3 Functional vs anatomical connectivity .................................................................................................... 55
8.1.4 Resting state fMRI .................................................................................................................................. 56
8.2 Multi-voxel pattern analyses (MVPA) ............................................................................................................ 56
8.2.1 ROI vs whole brain ................................................................................................................................. 57
8.2.2 The potential ........................................................................................................................................... 58
8.2.3 What do we measure? ............................................................................................................................. 59
8.3 Functional MRI adaption ................................................................................................................................ 60
9 Electromagnetic field of the brain ........................................................................................................................... 61
9.1 Electrophysiological activity of the brain ....................................................................................................... 61
9.1.1 From neurons to electromagnetic field ................................................................................................... 61
9.2 Electromagnetic field signals .......................................................................................................................... 62
9.2.1 Properties of the field signal ................................................................................................................... 62
9.2.2 Dimensions and resolution of the field signal ......................................................................................... 63
Spatial resolution................................................................................................................................................. 63
9.3 Brain dynamics vs. mind dynamics ................................................................................................................ 64
10 Electroencephalography and magnetoencephalography ..................................................................................... 65
10.1 Electroencephalography (EEG) ...................................................................................................................... 65
10.1.1 Electrodes ................................................................................................................................................ 65
10.1.2 Amplifier ................................................................................................................................................ 66
10.2 EEG summary ................................................................................................................................................. 66
10.3 Magnetoencephalography (MEG) ................................................................................................................... 67
3
Les avantages d'acheter des résumés chez Stuvia:
Qualité garantie par les avis des clients
Les clients de Stuvia ont évalués plus de 700 000 résumés. C'est comme ça que vous savez que vous achetez les meilleurs documents.
L’achat facile et rapide
Vous pouvez payer rapidement avec iDeal, carte de crédit ou Stuvia-crédit pour les résumés. Il n'y a pas d'adhésion nécessaire.
Focus sur l’essentiel
Vos camarades écrivent eux-mêmes les notes d’étude, c’est pourquoi les documents sont toujours fiables et à jour. Cela garantit que vous arrivez rapidement au coeur du matériel.
Foire aux questions
Qu'est-ce que j'obtiens en achetant ce document ?
Vous obtenez un PDF, disponible immédiatement après votre achat. Le document acheté est accessible à tout moment, n'importe où et indéfiniment via votre profil.
Garantie de remboursement : comment ça marche ?
Notre garantie de satisfaction garantit que vous trouverez toujours un document d'étude qui vous convient. Vous remplissez un formulaire et notre équipe du service client s'occupe du reste.
Auprès de qui est-ce que j'achète ce résumé ?
Stuvia est une place de marché. Alors, vous n'achetez donc pas ce document chez nous, mais auprès du vendeur dwrosanne. Stuvia facilite les paiements au vendeur.
Est-ce que j'aurai un abonnement?
Non, vous n'achetez ce résumé que pour €8,49. Vous n'êtes lié à rien après votre achat.
