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Table of Contents
Acknowledgements ... 3
Financial support ... 5
Abstract ... 6
Table of Contents ... 7
List of Tables ... 11
List of Figures ... 12
List of Abbreviations ... 13
Chapter 1. General introduction and rationale for this thesis. ... 16
1.1 Attention-Deficit/Hyperactivity Disorder, Autism Spectrum Disorder and their co-occurrence: an overview ... 16
1.1.1 Diagnostic criteria, differential diagnosis and comorbidity ... 16
1.1.2 Epidemiology and outcome ... 21
1.1.3 Aetiology ... 23
1.2 Cognitive profile and neuropsychological impairments in ADHD, ASD and the co-occurring presentation ... 27
1.2.1 Social cognition ... 28
1.2.2 Executive functioning and attentional profile ... 30
1.2.3 The role of response inhibition in the discussion of the overlap/distinctiveness between ASD and ADHD ... 35
1.3 Shared and specific structural and functional brain abnormalities between ADHD and ASD ... 41
1.3.1 Volumetric and surface-based measures findings ... 42
1.3.2 White matter microstructure abnormalities ... 49
1.3.3 Functional brain abnormalities ... 52
1.4 The aims of this thesis ... 57
Chapter 2. Experimental sample: clinical and neuropsychological characterization. .... 59
2.1 Participants ... 59
2.2 Clinical assessment ... 61
2.3 Neuropsychological assessment ... 62
2.3.1 Intellectual functioning (WISC-IV) ... 62
2.3.2 Alertness (TAP) ... 63
2.3.3 Divided Attention (TAP) ... 63
2.3.4 Go/No-Go (TAP) ... 64
2.3.5 Numerical Counting Stroop task ... 64
2.3.6 Digit Span (WISC-IV) ... 65
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2.3.8 Free –recall learning task ... 66
2.3.9 Revised Wisconsin Card Sorting Test (RCST) ... 66
2.3.10 Tower of London ... 66
2.3.11 Verbal fluency ... 67
2.3.12 Spaceship Delay Task ... 67
2.3.13 Stop-signal task ... 68
2.4 Statistical analyses ... 70
2.5 Results ... 71
2.5.1 Clinical assessment ... 71
2.5.2 Neuropsychological assessment ... 74
Chapter 3. Shared and specific grey matter volume abnormalities between ADHD and
ASD. ... 80
Abstract ... 82
3.1 Introduction ... 83
3.2 Materials and methods ... 85
3.2.1 Participants ... 85
3.2.2 Demographic data analysis ... 86
3.2.3 Anatomical image acquisition ... 87
3.2.4 Image quality control and pre-processing ... 87
3.2.5 VBM statistical analysis ... 88
3.3 Results ... 89
3.3.1 Participant characteristics ... 89
3.3.2 Analysis of total brain and total GMV/ WMV ... 90
3.3.3 VBM analysis of regional grey matter volume differences ... 91
3.3.4 Disorder-specificity of grey matter volume abnormalities ... 93
3.4 Discussion ... 95
Chapter 4. Shared and specific white matter microstructure abnormalities between
ADHD and ASD. ... 103
Abstract ... 105
4.1 Introduction ... 106
4.2 Materials and methods ... 109
4.2.1 Participants ... 109
4.2.2 MRI data acquisition ... 110
4.2.3 Pre-processing ... 110
4.2.4 TBSS processing ... 111
4.2.5 Statistical analysis ... 111
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4.3.1 Participant characteristics ... 112
4.3.2 Fractional anisotropy between-group comparison ... 113
4.3.3 Mean diffusivity between-group comparison ... 114
4.2 Discussion ... 114
Chapter 5. Shared and specific inhibition-related brain activation abnormalities between
ADHD and ASD. ... 120
Abstract ... 122
5. 1 Introduction ... 123
5.2 Materials and methods ... 125
5.2.1 Participants ... 125
5.2.2 Functional MRI paradigm: the stop-signal task ... 126
5.2.3 Demographic and behavioural data analysis ... 127
5.2.4 FMRI data acquisition ... 128
5.2.5 FMRI data analysis ... 128
5.3 Results ... 129
5.3.1 Demographic data and head motion ... 129
5.3.2 Stop-signal task performance ... 131
5.3.3 Within-group brain activations during successful inhibition ... 131
5.3.4 Between-groups comparison ... 132
5.4 Discussion ... 135
Chapter 6. General discussion and future directions. ... 141
6.1 Summary of studies ... 141
6.2 Absence of between-group differences in total brain volume, total grey matter volume and total white matter volume ... 144
6.3 Grey matter volume abnormalities in the precuneus and the thalamus in ADHD and in the precentral gyrus in ASD ... 145
6.4 Shared and specific white matter microstructure abnormalities in the corpus callosum ... 147
6.5 Reactive inhibition impairments in ADHD, but not ASD ... 148
6.6 Response inhibition places different demands on the fronto-parietal network in ASD and ADHD ... 149
6.7 Strengths and limitations of the studies ... 150
6.7.1 Strengths ... 150
6.7.2 Limitations ... 151
6.8 Implications of the findings and directions for future research ... 152
References ... 155
Appendix A: Diagnostic criteria for Attention-Deficit/Hyperactivity Disorder according to the DSM-5 (APA, 2013) ... 176
10 Appendix C: Structural and functional neuroimaging in attention-deficit/hyperactivity disorder
(Albajara Sáenz et al., 2018) ... 180
Appendix D: ADHD Rating Scale-IV (ADHD RS-IV; DuPaul et al., 1998) ... 188
Appendix E: Behaviour Rating Inventory of Executive Function (BRIEF; Gioia et al., 2000) ... 189
Appendix F: Social Responsiveness Scale (SRS; Constantino et al., 2003) ... 193
Appendix G: Developmental Coordination Disorder Questionnaire-French Canadian (DCDQ-FC; Martini et al., 2011) ... 196
