Functional magnetic resonance imaging in alert behaving monkeys [Elektronische Ressource] : blood-oxygen-level-dependent brain responses related to the processing of visual stimuli and voluntary eye movements / vorgelegt von Hendrik Dietrich

Hendrik Dietrich

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• Gesundheit

Informations

• Publié par: eberhard_karls_universitat_tubingen
• Publié le: 01 janvier 2006
• Nombre de lectures: 19
• Langue: Deutsch
• Poids de l'ouvrage: 6 Mo

Extrait

Functional Magnetic Resonance Imaging
in Alert Behaving Monkeys
Blood-oxygen-level-dependent brain responses related to the
processing of visual stimuli and voluntary eye movements



Dissertation



zur Erlangung des Grades eines Doktors
der Naturwissenschaften

der Fakultät für Biologie
und
der Medizinischen Fakultät
der Eberhard-Karls-Universität Tübingen

vorgelegt
von

Hendrik Dietrich
aus Kiel, Schleswig-Holstein

2006





















Tag der mündlichen Prüfung: 23. Juni 2006

Dekan der Fakultät für Biologie: Prof. Dr. Friedrich Schöffl
Dekan der Medizinischen Fakultät: Prof. Dr. Claus D. Claussen

1. Berichterstatter: Prof. Dr. Peter Thier
2. Berichterstatter: Prof. Dr. Werner J. Schmidt

Prüfungskommission: Prof. Dr. Peter Thier
Prof. Dr. Werner J. Schmidt Werner Lutzenberger Dr. Uwe Ilg Horst Herbert 
C o n t e n t s
1. INTRODUCTION.....................................................................................................6
1.1: Functional Magnetic Resonance Imaging (fMRI) ..................................................... 6
The magnetic resonance imaging (MRI) signal....................................................... 6
The blood oxygen level dependent (BOLD) contrast............................................... 9
How is the BOLD signal related to neural activity?................................................ 10
1.2: fMRI in monkeys........................................................................................................ 15
Motivation for fMRI studies in monkeys................................................................. 15
fMRI in anaesthetized monkeys............................................................................. 16
fMRI in alert behaving monkeys. ........................................................................... 17
Sources of image artefacts.................................................................................... 17
fMRI in humans vs. monkeys................................................................................. 18
1.3: Investigating visual processing and voluntary eye movements with fMRI......... 21
Visual field mapping............................................................................................... 21
Optic flow. .............................................................................................................. 22
Voluntary eye movements. .................................................................................... 24
2. MATERIAL & METHODS .....................................................................................28
2.1: Animals....................................................................................................................... 28
Subjects. ................................................................................................................ 28
Anaesthesia, surgical procedures and implants.................................................... 28
2.2: Experimental procedures ......................................................................................... 32
Experimental environment..................................................................................... 32
Body movements. .................................................................................................. 34
Training and behavioural control. .......................................................................... 36
2.3: Behavioural paradigms............................................................................................. 40
Visual field mapping paradigm............................................................................... 40
Optic flow paradigm. .............................................................................................. 40
Saccadic eye movement paradigm........................................................................ 41
Smooth pursuit eye movement paradigm.............................................................. 41
Implementation of the behavioural paradigms in the fMRI design. ....................... 41
2.4: Image acquisition ...................................................................................................... 43
Structural MR imaging. .......................................................................................... 43
Functional MR imaging. ......................................................................................... 43
  
2.5: Functional image analysis........................................................................................ 45
Standard procedures using software package ‘SPM2’.......................................... 45
Correction for multiple comparisons. ..................................................................... 46
Selection and pooling. ........................................................................................... 46
2.6: Superimposition, projection and evaluation of SPMs........................................... 47
Projection of SPMs onto structural images............................................................ 47
Projection of SPMs onto cortical surface reconstruction models. ......................... 48
Evaluation of SPMs by co-registration with rhesus monkey atlas......................... 48
F I G U R E S & T A B L E S ................................................................................50
3. RESULTS .............................................................................................................98
3.1: Presentation of BOLD responses............................................................................ 98
3.2: Visual field mapping ................................................................................................. 99
Representation of meridians of the visual field...................................................... 99
Representation of different degrees of eccentricity of the visual field. .................. 99
3.3: Optic flow ................................................................................................................. 100
3.4: Voluntary eye movements...................................................................................... 101
Saccadic eye movements.................................................................................... 101
Smooth pursuit eye movements. ......................................................................... 101
Saccadic vs. smooth pursuit eye movements. .................................................... 102
4. DISCUSSION & CONCLUSIONS.......................................................................104
4.1: Technical constraints ............................................................................................. 104
Image artefacts. ................................................................................................... 104
EPI sequence parameters. .................................................................................. 105
Coil configuration. ................................................................................................ 105
Eye-gaze-control.................................................................................................. 106
Presentation screen............................................................................................. 107
Auditory noise. ..................................................................................................... 107
Misalignment of functional and structural images................................................ 107
Misprojectiondata onto cortical surface reconstructions. ............... 108
Deviations of brain areas from atlas. ................................................................... 109
Definition of BOLD response peaks..................................................................... 109

  
4.2: Visual field mapping ............................................................................................... 110
Representation of meridians of the visual field.................................................... 110
Representation of different degrees of eccentricity of the visual field. ................ 111
4.3: Optic flow ................................................................................................................. 112
Areas MT/MST..................................................................................................... 112
Motion sensitivity.................................................................................................. 112
Cerebellum........................................................................................................... 115
4.4: Voluntary eye movements...................................................................................... 116
Comparison across studies. ................................................................................ 116
Areas LIP, FEF and SEF. .................................................................................... 116
Area 6. .............................