TABLE OF CONTENTS
Abbreviations………6
Acknowledgements ……….……….. 8
Foreword……… 9
A.INTRODUCTION : …..………...….. 11
I. Somatosensory system organization overview………..12
I.1 Ascending pathways ………12
I.1.1 Lemniscal pathway …..………12
I.1.2 Spinocerebellar pathways……… 14
I.2 Brief anatomy of the somatosensory cortices ...……….. 15
I.2.1 Cortex cells and histology..……….. 15
1.2.2 Functional organization of the somatosensory cortices ..…. 16
I.3 Brief anatomy of the Cerebellum………..19
I.3.1 Cells types and histology ……….. 19
1.3.2 Functional organization.………21
II. Brain Functional neuroimaging ……….23
II.1 Choice of technique ………24
II.2 Direct evaluation of neuronal activity (EEG/MEG) ………. 25
II.2.1 Electrical properties of neurons ………. 25
II.2.1.a Action potentials ………...26
II.2.2.b Post synaptic potentials ..……… 26
II.2.2 MEG/EEG recordings of neuronal activity………. 27
II.2.2.a Evoked potential in MEG/EEG…..……… 28
II.2.2.b Source reconstruction in MEG ...……….. 29
III. Change detection ………. 31
III.1 Oddball paradigms ………. 32
III.2 fMRI studies ………. 33
III.3 Electrophysiological studies ……….. 34
III.3.1 Change detection ERPs ……….. 34
III.3.1.a MMN ……….. 34
III.3.1.b P300 ……….. 36
III.3.1.c CNV ………... 39
III.3.1.d Interrelations/ local global/ clinical use ……….…… 41
III.4 Role of the cerebellum in tactile change detection ……….……….. 42
B. OBJECTIVES ……… 44
C. EXPERIMENTS ……….. 45
I. Multilevel Cortical Processing of Somatosensory Novelty ...……… 45
I.1 Rationale ……… 45
I.2 Material and Methods ...………. 46
I.2.1 Subjects………... 46
I.2.2 Experimental paradigm ………. 46
I.2.3 Data acquisition ………. 48
I.2.4 Data preprocessing and sensor space analysis ………. 49
I.2.5 Source reconstruction and source space analysis…… 52
I.2.6 Correlation analysis ……… 53
I.3 Results ………...………. 54
I.3.1 magnetic somatosensory mismatch negativity…...….. 54
1.3.2 P300…...……….. 58
1.3.3 Expectation ………...……….. 60
1.3.3.1 Intra-block CMV………. 60
1.3.3.2 Inter-block CMV………... 60
1.3.4 Correlations………. 60
I.4 Discussion ………. 62
II. Early change detection mechanisms ……….. 68
II.1 Rationale ……….. 68
II.2 Material and Methods………... 70
II.2.1 Subjects ………. 70
II.2.2 Experimental paradigm..………. 70
II.2.3 Data acquisition ……… 74
II.2.4 Data preprocessing and sensor space analysis……… 74
II.3 Results………... 77
II.3.1 Oddball condition ……… 77
II.3.2 Long_IBI_Oddball condition……… 78
II.3.3 Dual condition……… 80
II.3.4 SEFs elicited by Double stimuli in Oddball, Dual and Alone conditions……… 81
II.3.5 Omissions condition ……….. 83
II.4 Discussion ……...……… 84
II.4.1 SII cortex is involved in tactile early change detection………84
II.4.2 Attenuation of cSII cortex responses by successive tactile stimuli and the role of adaptation in sMMN genesis ………..87
II.4.3 SII cortex detects early tactile change under the predictive coding framework……… 88
III. Cerebellar modulation of early tactile change detection ……… 91
III.1 Rationale ……… 91
III.2 Material and Methods ………. 95
III.2.1 Participants……… 95
III.2.2 Experimental paradigm ...……….. 96
III.2.3 Data acquisition ……… 98
III.2.4 Data preprocessing and sensor-space evoked fields………... 98
III.2.5 Source reconstruction ..……… 99
III.2.6 Statistical assessments ...………. 100
III.3 Results ……….. 102
III.3.1 Evoked responses to standards in somatosensory and auditory paradigms………..……… 102 III.3.1.a Somatosensory evoked responses……….. 102
III.3.1.b Auditory evoked responses ..………. 103
III.3.2 Early change detection………105
III.3.2.a Early somatosensory change detection… 105 III.3.2.b Early auditory change detection ……….. 106
III.4 Discussion ……...………... 108
III.4.1 MEG evoked responses in control subjects and FRDA patients .. ……… 108
III.4.2 Early somatosensory change detection is impaired in FRDA and correlates with the size of GAA1 triplet expansion
………..………112
III.4.3 Role of the cerebellum within the somatosensory change detection network……...……… 114
D. GENERAL DISCUSSION………. 116 I. Functional neuro-anatomy of somatosensory change detection..……. 116 II. Somatosensory change detection under predictive coding theory…. 122 II.1 Bayesian brain and predictive coding theory…...………. 123 II.2 Response to stimulus and stimulus predictability...…………... 124 II.3 Prediction according to the context…...……….. 125 II.4 Response to omitted stimuli and predictions…...………. 126 II.5 Predictive coding and stimulus intervals ……...………. 127 II.6 Multimodal areas roles under the predictive coding ………… 128 II.6.1 Attention and prediction …..………. 128 II.6.2 Representation and confrontation of reality …...….. 130 III. Conclusions and perspectives …..………... 132 Reference list ………134
