Spectral and Coherence Estimates on Electroencephalogram recordings during arithmetical tasks

154 Pages·2009·3.31 MB·English

Spectral and Coherence Estimates
on Electroencephalogram recordings
during arithmetical tasks
Ana Filipa Teixeira Borges
Disserta¸c˜ao apresentada na Faculdade de Ciˆencias
e Tecnologia da Universidade Nova de Lisboa para
obten¸c˜ao do Grau de Mestre em Engenharia Biom´edica
Coordenadores: Prof. Carla Quint˜ao Silva
LISBOA
2009
2
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A minha fam´ılia querida
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Acknowledgments
First of all, I would like to thank my thesis advisors. In particular, Prof. Carla
Silva for her enthusiastic way of teaching, all her efforts and the way she believed in me to
this work since the first moment and Prof. Giuseppe Baselli, for his endeavors attempts
to make this work possible and supporting guidance both, during my stay in Italy and the
work developed here. I thank also Professor Ma´rio Secca for his efforts in bureaucratic
procedures regarding my stay abroad.
I thank also Marcella Lagan`a and Roberta Carabalona for their help and the data
they provide me in the Polo Tecnologico della Fondazione Don Gnocchi.
I am grateful also to Ana Carolina Sousa, the person responsible for the acquisi-
tion of the data in the Instituto de Biof´ısica e Engenharia Biom´edica.
A special thanking word to John Peter for his valuable suggestions on the arith-
metical protocol and to all the volunteers of this work.
To my cousin, Pedro Teixeira, a thanking word for introducing me in the Latex
typesetting world.
So many thank’s to my friends, you know who you are, I must say that more
than the support and all the moments we shared, every singularity of their personalities
has inspired me in a profound way, I like so much each one exactly the way they are. I
would like to thank Iolanda and Mariana for all the time we lived together, friends can
really be family.
I express my gratitude also to all my family and specially to my grandma and
grandpa, even though they are far away I feel them all around.
A thanking word also to Enrico, for the way he is always present in my ups and
nows and shares with me everything. I would like to thank also the Scofone family for
their support.
I thank my little sister, she might think Science is for nerds but her presence and
constant support are a source of inspiration and proud to me.
In the end but not the least, I deeply, deeply thank my mother, she gave every-
thing I am and she is everything I want to be.
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iv 0.Acknowledgments
Contents
Acknowledgments iii
Abstract xix
1 Preface 1
1.1 Context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Scope and Work Developed . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Outline of the Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 The Brain:Anatomy, Physiology and Functional Connectivity 5
2.1 Anatomy and Physiology of the Brain . . . . . . . . . . . . . . . . . . . . . 5
2.1.1 Brain and Cognition . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.2 Cytology of the Brain . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 Neurophysiological Background of the Brain Signals . . . . . . . . . . . . . 11
2.3 Brain’s Functional Connectivity . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3.1 Introduction to Brain Networks . . . . . . . . . . . . . . . . . . . . 14
3 Methods of Acquisition of the Signals of the Brain - EEG Acquisition 17
3.1 First Steps and Recent Developments- Brief Review of Electroencephalo-
gram History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.2 EEG Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.2.1 EEG Rhythms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.2.2 Variability of EEG . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.3 Protocols in EEG Acquisition . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.3.1 Electrodes and Head Stage . . . . . . . . . . . . . . . . . . . . . . . 21
3.3.2 Preprocessing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.3.3 Data Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.4 EEG in the context of other Brain study techniques . . . . . . . . . . . . . 25
3.4.1 EEGandanoverviewoftheHemodynamicResponsebasedtechniques 26
3.4.2 EEG and MEG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
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3.5 EEG Temporal and Frequential Analysis . . . . . . . . . . . . . . . . . . . 29
4 Coherence on Electroencephalography 33
4.1 Brief Historical Remarks on EEG Coherence . . . . . . . . . . . . . . . . . 33
4.2 Concept of EEG Coherence . . . . . . . . . . . . . . . . . . . . . . . . . . 34
4.3 EEG Coherence as a measure of Brain Functional Connectivity . . . . . . . 37
4.4 Methods of Coherence Estimation . . . . . . . . . . . . . . . . . . . . . . . 38
4.5 Stationary analysis: Fourier Approaches . . . . . . . . . . . . . . . . . . . 39
4.5.1 Continuous Fourier Transform . . . . . . . . . . . . . . . . . . . . . 39
4.5.2 Discrete Fourier Transform . . . . . . . . . . . . . . . . . . . . . . . 41
4.6 Spectrum Estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.6.1 Windowing - Frequency smoothing . . . . . . . . . . . . . . . . . . 44
4.6.2 Averaging the data - Temporal Smoothing . . . . . . . . . . . . . . 47
4.6.3 Welch’s Overlapping Segment Averaging (WOSA) Estimation . . . 47
4.6.4 Statistical Properties of the Fourier Approaches . . . . . . . . . . . 48
4.6.5 Thomson’s method - Multitaper’s approach . . . . . . . . . . . . . 49
4.7 Dynamical analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
4.7.1 Short-time Fourier and Gabor analysis . . . . . . . . . . . . . . . . 51
4.7.2 Wavelet analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
4.8 EEG Coherence Significance and Drawbacks in EEG Coherence Studies . . 57
4.9 EEG Coherence in Neurocognitive and Clinical findings . . . . . . . . . . . 59
5 Simulation Data 61
5.1 Experimental Paradigm . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
5.1.1 Apart on Confidence Intervals . . . . . . . . . . . . . . . . . . . . . 62
5.2 Cosine Based Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
5.2.1 Phase modulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
5.2.2 Integral Phase Modulation . . . . . . . . . . . . . . . . . . . . . . . 64
5.2.3 Amplitude Modulation . . . . . . . . . . . . . . . . . . . . . . . . . 64
5.2.4 Modulation with additive noise . . . . . . . . . . . . . . . . . . . . 65
5.2.5 Brief Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
5.3 Mix Spectrum Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
5.4 Interpretation and Discussion of the results . . . . . . . . . . . . . . . . . . 67
6 Mental Calculation 71
6.1 Mental calculation substrate . . . . . . . . . . . . . . . . . . . . . . . . . . 71
6.2 Comprehensive state-of-art . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
6.3 Mental calculation in EEG studies . . . . . . . . . . . . . . . . . . . . . . . 74
CONTENTS vii
7 Mental Calculation: Interval Stimuli task 75
7.1 Experimental Protocol and Paradigm . . . . . . . . . . . . . . . . . . . . . 75
7.2 Stationary Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
7.2.1 Spectral Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
7.2.2 Coherence Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
7.2.3 Some Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
7.3 Dynamical Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
7.3.1 Experimental Procedure . . . . . . . . . . . . . . . . . . . . . . . . 83
7.3.2 Main Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
7.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
8 Mental Calculation: Counting backwards task 91
8.1 Experimental Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
8.1.1 EEG Acquisition and Participants . . . . . . . . . . . . . . . . . . . 91
8.1.2 Cognitive task: Counting Backwards . . . . . . . . . . . . . . . . . 92
8.2 Experimental Paradigm and EEG Processing . . . . . . . . . . . . . . . . . 93
8.2.1 Frequency Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
8.2.2 Study of Spectral Power and Coherence . . . . . . . . . . . . . . . . 94
8.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
8.3.1 Power Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
8.3.2 Coherence Results . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
8.4 Discussion of the results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
9 General Discussion and Conclusion 107
9.1 Discussion and Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
9.2 Contributes of the work done . . . . . . . . . . . . . . . . . . . . . . . . . 108
9.3 Perspectives of future work . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
Appendix 1 125
Appendix 2 131
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