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Alexandre Gramfort
alexandre.gramfort@inria.fr
Learning representations
from neural signals
MAIN conf. - Dec. 2019
Alex Gramfort Learning representations from neural signals
Neurons as current generators
2
Current
Large cortical pyramidal cells organized in
macro-assemblies with their dendrites
normally oriented to the local
cortical surface
White matter
Gray matter
Alex Gramfort Learning representations from neural signals
Neurons as current generators
2
Current
Large cortical pyramidal cells organized in
macro-assemblies with their dendrites
normally oriented to the local
cortical surface
White matter
Gray matter
Q = I × d
(10 to 100 nAm) with
the equivalent current
dipole (ECD) model
B
Magnetic Field
Neural
Current
(post synaptic)
Equivalent
Current
Dipole
E
Electric Field
Neural
Current
(post synaptic)
Equivalent
Current
Dipole
Alex Gramfort Learning representations from neural signals
Electro- & Magneto-encephalography
3
B
Neural
Current
(post synaptic)
Equivalent
Current
Dipole
dB/dz
MEG recordings
First EEG
recordings
in 1929
by H. Berger
Hôpital La Timone
Marseille, France
E
Neural
Current
(post synaptic)
Equivalent
Current
Dipole
V EEG recordings
Alex Gramfort Learning representations from neural signals
Stereotaxic EEG (sEEG)
4
Intracranial electrodes;
5 to 15 contacts per electrode
Around 10 electrodes are implanted Stereotaxic Implantation
MAIN Conf Talk: Learning representations from neural signals
μ rhythm
[T. Dupré laTour, L.Tallot, L. Grabot,V. Doyère,V. vanWassenhove,Y. Grenier,A. Gramfort,
(2017) PLOS Computational biology]
μ rhythm
[T. Dupré laTour, L.Tallot, L. Grabot,V. Doyère,V. vanWassenhove,Y. Grenier,A. Gramfort,
(2017) PLOS Computational biology]
μ rhythm
CFC: High frequency bursts coupled with slow waves
[T. Dupré laTour, L.Tallot, L. Grabot,V. Doyère,V. vanWassenhove,Y. Grenier,A. Gramfort,
(2017) PLOS Computational biology]
μ rhythm
CFC: High frequency bursts coupled with slow waves
Neural signals exhibit
diverse and complex
morphologies
Alex Gramfort Learning representations from neural signals
“Textbook” brain rythms
6
Gamma
(> 25 Hz)
Beta
(12-25 Hz)
Alpha
(8-12 Hz)
Theta
(4-8 Hz)
Delta
(1-4 Hz)
Alex Gramfort Learning representations from neural signals
Fourier Fallacy [Jasper 48]
7
Power Spectra:Waveform:Topography:
Alex Gramfort Learning representations from neural signals
Fourier Fallacy [Jasper 48]
7
«Even though it may be possible to analyze the complex forms of
brain waves into a number of different sine-wave
frequencies, this may lead only to what might be termed a
“Fourier fallacy”, if one assumes ad hoc that all of the
necessary frequencies actually occur as periodic phenomena in
cell groups within the brain. »
Jasper, 1948
Power Spectra:Waveform:Topography:
Alex Gramfort Learning representations from neural signals
Fourier Fallacy [Jasper 48]
7
«Even though it may be possible to analyze the complex forms of
brain waves into a number of different sine-wave
frequencies, this may lead only to what might be termed a
“Fourier fallacy”, if one assumes ad hoc that all of the
necessary frequencies actually occur as periodic phenomena in
cell groups within the brain. »
Jasper, 1948
Harmonics
Power Spectra:Waveform:Topography:
Alex Gramfort Learning representations from neural signals
Outline
8
S. Chambon,V.Thorey, P. J.Arnal, E. Mignot,A. Gramfort. (2018), DOSED:
a deep learning approach to detect multiple sleep micro-events in EEG
signal,Arxiv 2500163
S. Chambon, M. Galtier, P.Arnal, G.Wainrib, A. Gramfort (2018),A deep
learning architecture for temporal sleep stage classification using
multivariate and multimodal time series, IEEE Trans. Neural Systems
and Rehabilitation Engineering
T. Dupré la Tour,  T. Moreau, M. Jas,A. Gramfort (2018), Multivariate
Convolutional Sparse Coding for Electromagnetic Brain Signals, Proc.
NeurIPS Conf.
M. Jas,T. Dupré la Tour, U. Simsekli,A. Gramfort (2017), Learning the
Morphology of Brain Signals Using Alpha-Stable Convolutional Sparse
Coding, Proc. NeurIPS Conf.
Polysomnography exam:
I Electroencephalography (EEG)
I Electrooculography (EOG)
I Electromyography (EMG)
I · · ·
Preliminary exam in sleep studies:
I sleep disorders
I psychiatric disorders...
Polysomnographie
“Deep” supervised learning on sleep EEG data:
Unsupervised convolutional sparse coding:
Deep supervised learning
on sleep EEG data
1
Spindle
K-complex
Alex Gramfort Learning representations from neural signals
Polysomnography (PSG)
• Clinical exam
• Electrophysiological signals
10
Electro-oculography
(EOG)
Electro-encephalography
(EEG)
Electro-myography
(EMG)
Alex Gramfort Learning representations from neural signals
Polysomnography (PSG)
• Clinical exam
• Electrophysiological signals
10
Electro-oculography
(EOG)
Electro-encephalography
(EEG)
Electro-myography
(EMG)
Routinely annotated by
sleep experts
Alex Gramfort Learning representations from neural signals
2 types of annotations
Hypnogram

of sleep stages
Micro-events:
Spindles, K-complex etc.
11
Alex Gramfort Learning representations from neural signals
2 types of annotations
Hypnogram

of sleep stages
Micro-events:
Spindles, K-complex etc.
11
Classification problem
Alex Gramfort Learning representations from neural signals
2 types of annotations
Hypnogram

of sleep stages
Micro-events:
Spindles, K-complex etc.
11
Classification problem
Joint detection and classification problem
MAIN Conf Talk: Learning representations from neural signals
Alex Gramfort Learning representations from neural signals
Objective
13
PSG data
Alex Gramfort Learning representations from neural signals
Objective
13
x 2 X
PSG data
Alex Gramfort Learning representations from neural signals
Objective
13
Learn: ˆf : X ! Y
Y = {Awake, REM, Stage 1, Stage 2, etc.}
x 2 X
PSG data
Alex Gramfort Learning representations from neural signals
Objective
13
Learn: ˆf : X ! Y
Y = {Awake, REM, Stage 1, Stage 2, etc.}
x 2 X
PSG data
Multiclass prediction problem
Input is multiple time series
Alex Gramfort Learning representations from neural signals
and many more….
An old yet timely problem
14
C. Berthomier, X. Drouot, M. Herman-Stoïca, et al. ,“Automatic analysis of single-channel sleep EEG:
validation in healthy individuals.,” Sleep, vol. 30, no. 11, pp. 1587–1595, 2007.
O.Tsinalis, P. M. Matthews, andY. Guo,“Automatic Sleep Stage Scoring Using Time-Frequency Analysis and
Stacked Sparse Autoencoders,” Annals of Biomedical Engineering, vol. 44, no. 5, pp. 1587–1597, 2016.
J. B. Stephansen, A.Ambati, E. B. Leary, et al.,“The use of neural networks in the analysis of sleep stages and
the diagnosis of narcolepsy,” CoRR, vol. abs/1710.02094, 2017.
A.Vilamala, K. H. Madsen, and L. K. Hansen,“Deep convolutional neural networks for interpretable analysis of
EEG sleep stage scoring,” 2017 IEEE Workshop on Machine Learning for Signal Processing (MLSP)
S.Biswal, J.Kulas, H.Sun, B.Goparaju, M.B.Westover, M.T.Bianchi and J. Sun,“SLEEPNET: automated sleep
staging system via deep learning,” arXiv:1707.08262, 2017.
H. Dong,A. Supratak,W. Pan, C.Wu, P. M. Matthews, andY. Guo,“Mixed Neural Network Approach for
Temporal Sleep Stage Classification,” arXiv:1610.06421v1, vol. 1, 2016.
O.Tsinalis, P.M. Matthews,Y. Guo and S.Zafeiriou,“Automatic Sleep Stage Scoring with Single-Channel EEG
Using Convolutional Neural Networks,” arXiv:1610.01683, pp. 1–10, 2016.
A. Supratak, H. Dong, C.Wu, andY. Guo,“Deepsleepnet: a model for automatic sleep stage scoring based on
raw single-channel EEG,” IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2017.
T. Lajnef, S. Chaibi, P. Ruby, et al. ,“Learning Machines and Sleeping Brains:Automatic Sleep Stage Classification
using Decision-Tree Multi-Class SupportVector Machines,” Journal of Neuroscience Methods, 2015.
Alex Gramfort Learning representations from neural signals
and many more….
An old yet timely problem
14
C. Berthomier, X. Drouot, M. Herman-Stoïca, et al. ,“Automatic analysis of single-channel sleep EEG:
validation in healthy individuals.,” Sleep, vol. 30, no. 11, pp. 1587–1595, 2007.
O.Tsinalis, P. M. Matthews, andY. Guo,“Automatic Sleep Stage Scoring Using Time-Frequency Analysis and
Stacked Sparse Autoencoders,” Annals of Biomedical Engineering, vol. 44, no. 5, pp. 1587–1597, 2016.
J. B. Stephansen, A.Ambati, E. B. Leary, et al.,“The use of neural networks in the analysis of sleep stages and
the diagnosis of narcolepsy,” CoRR, vol. abs/1710.02094, 2017.
A.Vilamala, K. H. Madsen, and L. K. Hansen,“Deep convolutional neural networks for interpretable analysis of
EEG sleep stage scoring,” 2017 IEEE Workshop on Machine Learning for Signal Processing (MLSP)
S.Biswal, J.Kulas, H.Sun, B.Goparaju, M.B.Westover, M.T.Bianchi and J. Sun,“SLEEPNET: automated sleep
staging system via deep learning,” arXiv:1707.08262, 2017.
H. Dong,A. Supratak,W. Pan, C.Wu, P. M. Matthews, andY. Guo,“Mixed Neural Network Approach for
Temporal Sleep Stage Classification,” arXiv:1610.06421v1, vol. 1, 2016.
O.Tsinalis, P.M. Matthews,Y. Guo and S.Zafeiriou,“Automatic Sleep Stage Scoring with Single-Channel EEG
Using Convolutional Neural Networks,” arXiv:1610.01683, pp. 1–10, 2016.
A. Supratak, H. Dong, C.Wu, andY. Guo,“Deepsleepnet: a model for automatic sleep stage scoring based on
raw single-channel EEG,” IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2017.
T. Lajnef, S. Chaibi, P. Ruby, et al. ,“Learning Machines and Sleeping Brains:Automatic Sleep Stage Classification
using Decision-Tree Multi-Class SupportVector Machines,” Journal of Neuroscience Methods, 2015.
To be compared
Alex Gramfort Learning representations from neural signals
and many more….
An old yet timely problem
14
Obj: learn from raw multimodal and multivariate signals
C. Berthomier, X. Drouot, M. Herman-Stoïca, et al. ,“Automatic analysis of single-channel sleep EEG:
validation in healthy individuals.,” Sleep, vol. 30, no. 11, pp. 1587–1595, 2007.
O.Tsinalis, P. M. Matthews, andY. Guo,“Automatic Sleep Stage Scoring Using Time-Frequency Analysis and
Stacked Sparse Autoencoders,” Annals of Biomedical Engineering, vol. 44, no. 5, pp. 1587–1597, 2016.
J. B. Stephansen, A.Ambati, E. B. Leary, et al.,“The use of neural networks in the analysis of sleep stages and
the diagnosis of narcolepsy,” CoRR, vol. abs/1710.02094, 2017.
A.Vilamala, K. H. Madsen, and L. K. Hansen,“Deep convolutional neural networks for interpretable analysis of
EEG sleep stage scoring,” 2017 IEEE Workshop on Machine Learning for Signal Processing (MLSP)
S.Biswal, J.Kulas, H.Sun, B.Goparaju, M.B.Westover, M.T.Bianchi and J. Sun,“SLEEPNET: automated sleep
staging system via deep learning,” arXiv:1707.08262, 2017.
H. Dong,A. Supratak,W. Pan, C.Wu, P. M. Matthews, andY. Guo,“Mixed Neural Network Approach for
Temporal Sleep Stage Classification,” arXiv:1610.06421v1, vol. 1, 2016.
O.Tsinalis, P.M. Matthews,Y. Guo and S.Zafeiriou,“Automatic Sleep Stage Scoring with Single-Channel EEG
Using Convolutional Neural Networks,” arXiv:1610.01683, pp. 1–10, 2016.
A. Supratak, H. Dong, C.Wu, andY. Guo,“Deepsleepnet: a model for automatic sleep stage scoring based on
raw single-channel EEG,” IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2017.
T. Lajnef, S. Chaibi, P. Ruby, et al. ,“Learning Machines and Sleeping Brains:Automatic Sleep Stage Classification
using Decision-Tree Multi-Class SupportVector Machines,” Journal of Neuroscience Methods, 2015.
To be compared
Alex Gramfort Learning representations from neural signals
Proposed approach
Features
• Convolutional Neural Net (CNN): Frequency content
Spatial context
• Multivariate signals: spatial filtering (like ICA would do)
• Multimodal inputs: different pipelines for EEG, EOG and EMG
Temporal context
• Concatenate features of neighboring samples
[A deep learning architecture for temporal sleep stage classification using multivariate and multimodal
time series. S. Chambon, M. N. Galtier, P. J.Arnal, G.Wainrib,A. Gramfort. IEEE TSRNE 2018]
15
Alex Gramfort Learning representations from neural signals
Problem formulation
16
ˆf 2 argminf2F Ex,y2X⇥Y [`(y, f(x))]
Risk minimization:
Alex Gramfort Learning representations from neural signals
Problem formulation
16
ˆf 2 argminf2F Ex,y2X⇥Y [`(y, f(x))]
Risk minimization:
F• : a class of models (neural networks architecture).
Alex Gramfort Learning representations from neural signals
Problem formulation
16
ˆf 2 argminf2F Ex,y2X⇥Y [`(y, f(x))]
Risk minimization:
F• : a class of models (neural networks architecture).
`• : loss.We use the categorical cross-entropy.
• Minimized on a training set using backpropagation and
online stochastic gradient descent.
shape = (C, T) Spatial Filtering
shape = (C’, T) Spatial Filtering
EEG/EOG
EMG
Input
Conv/Relu/MP
Softmax
Conv/Relu/MP
𝜙C 𝜓
𝜙
𝜙T
shape = (C, T) Spatial Filtering
shape = (C’, T) Spatial Filtering
EEG/EOG
EMG
Input
Conv/Relu/MP
Softmax
Conv/Relu/MP
𝜙C 𝜓
𝜙
𝜙T
shape = (C, T) Spatial Filtering
shape = (C’, T) Spatial Filtering
EEG/EOG
EMG
Input
Conv/Relu/MP
Softmax
Conv/Relu/MP
𝜙C 𝜓
𝜙
𝜙T
shape = (C, T) Spatial Filtering
shape = (C’, T) Spatial Filtering
EEG/EOG
EMG
Input
Conv/Relu/MP
Softmax
Conv/Relu/MP
𝜙C 𝜓
𝜙
𝜙T
shape = (C, T) Spatial Filtering
shape = (C’, T) Spatial Filtering
EEG/EOG
EMG
Input
Conv/Relu/MP
Softmax
Conv/Relu/MP
𝜙C 𝜓
𝜙
𝜙T
shape = (C, T) Spatial Filtering
shape = (C’, T) Spatial Filtering
EEG/EOG
EMG
Input
Conv/Relu/MP
Softmax
Conv/Relu/MP
𝜙C 𝜓
𝜙
𝜙T
shape = (C, T) Spatial Filtering
shape = (C’, T) Spatial Filtering
EEG/EOG
EMG
Input
Conv/Relu/MP
Softmax
Conv/Relu/MP
𝜙C 𝜓
𝜙
𝜙T
shape = (C, T) Spatial Filtering
shape = (C’, T) Spatial Filtering
EEG/EOG
EMG
Input
Conv/Relu/MP
Softmax
Conv/Relu/MP
𝜙C 𝜓
𝜙
𝜙T
shape = (C, T) Spatial Filtering
shape = (C’, T) Spatial Filtering
EEG/EOG
EMG
Input
Conv/Relu/MP
Softmax
Conv/Relu/MP
𝜙C 𝜓
𝜙
𝜙T
shape = (C, T) Spatial Filtering
shape = (C’, T) Spatial Filtering
EEG/EOG
EMG
Input
Conv/Relu/MP
Softmax
Conv/Relu/MP
𝜙C 𝜓
𝜙
𝜙T
Block 1
Conv, ReLU, Max Pooling
Input
Block 2
Alex Gramfort Learning representations from neural signals
Model parameters
23
Alex Gramfort Learning representations from neural signals
Model parameters
23
Spatial filtering
Alex Gramfort Learning representations from neural signals
Model parameters
23
Spatial filtering
Conv. layer 1
Alex Gramfort Learning representations from neural signals
Model parameters
23
Spatial filtering
Conv. layer 1
Conv. layer 2
zt
𝜙
𝜓
0 30
yt
zt k zt zt+k
Time (s)
𝜙𝜙 𝜙
𝜓
Sequence of inputsEEGChannels
F4
F3
C3
C4
O1
O2
-60 -30 0 30 60 90
yt
zt k zt zt+k
Time (s)
𝜙𝜙 𝜙
𝜓
Sequence of inputsEEGChannels
F4
F3
C3
C4
O1
O2
-60 -30 0 30 60 90
yt
We pool the
representations from
neighboring windows
Experiments…
Alex Gramfort Learning representations from neural signals
Experimental setup
• Data
• MASS - session 3: O’Reilly et al. 2014
• http://www.ceams-carsm.ca/en/MASS
• 61 records, ~10h / record
• Total number of samples about 60,000 (like for MNIST)
• Preprocessing
• lowpass filtering (30Hz)
• downsampling 128Hz
27
Alex Gramfort Learning representations from neural signals
Experimental setup
• Cross validation
• 5 splits
• 41 records for training, 10 for validation, 10 for testing
• Baselines
• Gradient boosting: Hand crafted features (mean, variance…
relative power in frequency bands) [Lajnev et al. 2015]
• [Tsinalis et al. 2016]: deep convolutional network
• [Supratak et al. 2017]: deep convolutional network
processing low and high frequency contents specifically
28
Alex Gramfort Learning representations from neural signals
Influence of spatial context
29
Influence of temporal context
30
Influence of temporal context
30
• Temporal context helps
• But less when using more channels
Alex Gramfort Learning representations from neural signals
Performance vs SoTA
31
Performance:
Computational
efficiency:
Alex Gramfort Learning representations from neural signals
Performance vs SoTA
31
Performance:
Computational
efficiency:
• Networks outperform hand crafted features
with gradient boosting
• Combining all modalities helps (multivariate)
• SoTA is obtained with less parameters (fast)
Alex Gramfort Learning representations from neural signals
“Opening” the black box
32
Confusion matrix:
N1 is hard
Alex Gramfort Learning representations from neural signals
“Opening” the black box
32
Confusion matrix:
N1 is hard
“Hiding” frequencies from the network:
network has learnt scoring rules
Start time End time Type
Joint detection and
classification of micro-events
[A deep learning architecture to detect events in EEG signals during sleep.
S. Chambon,V.Thorey, P. J.Arnal, E. Mignot,A. Gramfort. MLSP 2018]
[DOSED: a deep learning approach to detect multiple sleep micro-events in EEG signal,.
S. Chambon,V.Thorey, P. J.Arnal, E. Mignot,A. Gramfort. Arxiv 2500163]
Start time End time Type
Joint detection and
classification of micro-events
Objective: Predict
what and when at
the same time
[A deep learning architecture to detect events in EEG signals during sleep.
S. Chambon,V.Thorey, P. J.Arnal, E. Mignot,A. Gramfort. MLSP 2018]
[DOSED: a deep learning approach to detect multiple sleep micro-events in EEG signal,.
S. Chambon,V.Thorey, P. J.Arnal, E. Mignot,A. Gramfort. Arxiv 2500163]
Alex Gramfort Learning representations from neural signals
Spindles K-complex
Spindles and K-complexes in N2 stage
• Different types, durations, scales
• Associated to certain sleep stages and sleep disorders
Micro-events
34
Why is it hard?
Why should you care?
Alex Gramfort Learning representations from neural signals
State of the art
• Signal processing:
• Band-pass filtering + thresholding
• Decomposition into components
• Shallow learning algorithms:
• Clustering
• Binary classifier
35
[Parekh et al. 2017,
Lajnef et al. 2017]
[Ray et al. 2015,Wamsley et
al. 2012,Wendt et al. 2012,
Mölle et al. 2011, Nir et al.
2011, Ferrarelli et al. 2007]
[Patti et al. 2017]
[Patti et al. 2015,
Lachner-Piza et al. 2018]
None of these works use deep learning
Alex Gramfort Learning representations from neural signals
DOSED algorithm
Inspired by: YOLO and SSD
1. Predict: type, start & end
2. Allows for multiple types of events
3. Detection and classification in one pass
4. Convolutional network
36
[Redmon et al. 2016,
Liu et al. 2015]
Alex Gramfort Learning representations from neural signals
Event detector
𝜓loc : conv. layerInput 𝜙: CNN 𝜓clf : conv. layer
Setup Model
Default events
37
Alex Gramfort Learning representations from neural signals
d1 d2 dNd
Loss: localization + classification
!38
Alex Gramfort Learning representations from neural signals
d1 d2 dNd
Default events overlapping with true events
Loss: localization + classification
!39
Alex Gramfort Learning representations from neural signals
d1 d2 dNd
Remaining default events
Loss: localization + classification
!40
Default events overlapping with true events
Alex Gramfort Learning representations from neural signals
Evaluation
•By event metrics



•Based on Intersection
over Union (IoU)

•Precision, Recall, F1
Predicted event
True event
41
[Warby et al. 2014] IoU < 𝜕 => False positive
IoU > 𝜕 => True positive
Alex Gramfort Learning representations from neural signals
3 datasets
SS2

[O’Reilly et al. 2014]
SSC

[Andlauer et al. 2013]
WSC
[Young et al. 2008]
# Subjects 19 26 30
Age 23.6 ± 3.7 52.2 ± 14.3 65.2 ± 8.2
Aplit

(train, val, test)
10, 5, 4 15, 5, 6 19, 5, 6
Events
spindles

K-complexes
spindles spindles
42
General benchmark
Alex Gramfort Learning representations from neural signals
Illustration
44
True event
Predicted event
Alex Gramfort Learning representations from neural signals
Illustration
44
True event
Predicted event
Alex Gramfort Learning representations from neural signals
Joint detection
45
Joint detection does not deteriorate performance
Convolutional Sparse Coding (CSC)
for learning the morphology of
neural signals
2
Code: https://alphacsc.github.io
Multivariate Convolutional Sparse Coding for Electromagnetic Brain Signals, (2018),
T. Dupré laTour, T. Moreau, M. Jas,A. Gramfort, Proc. NeurIPS Conf.
Learning the Morphology of Brain Signals Using Alpha-Stable Convolutional Sparse Coding,
(2017), M. Jas,T. Dupré laTour, U. Simsekli,A. Gramfort, Proc. NeurIPS Conf.
Alex Gramfort Learning representations from neural signals
Signal representations
▪Sparse representations: wavelet basis
▪Sparse coding / dictionary learning
▪Shift-invariant representations
▪In neurophysiology:
▪ Matching of time-invariant filters (MOTIF)
▪ Multivariate orthogonal matching pursuit
▪ Matching pursuit and heuristics
▪ Sliding window machine
▪ Adaptive waveform learning
47
[Morlet 70’, Meyer 80’, Mallat 90’ etc.]
[Olshausen and Field, 1996, Elad and Aharon, 2006]
[Lewicki and Sejnowski, 1999, Grosse et al, 2007]
[Jost et al, 2006]
[Gips et al, 2017]
[Hitziger et al, 2017]
[Barthélemy et al, 2012]
[Brokmeier and Principe, 2016]
Alex Gramfort Learning representations from neural signals
Convolutional sparse coding
48
[Grosse et al, 2007]
Alex Gramfort Learning representations from neural signals
Convolutional sparse coding
49
[Grosse et al, 2007]
Alex Gramfort Learning representations from neural signals
Convolutional sparse coding
50
[Grosse et al, 2007]
Alex Gramfort Learning representations from neural signals
Optimization strategy
51
Block-coordinate descent:
Alex Gramfort Learning representations from neural signals
Optimization strategy
51
Block-coordinate descent:
[Kavukcuoglu et al, 2010]
[Chalasani et al, 2013]
[Bristow et al, 2013]
[Wohlberg, 2016]
[Jas et al, 2017]
[Dupré la Tour et al, 2018]
▪ Z-step
▪ GCD
▪ FISTA
▪ ADMM
▪ ADMM + FFT
▪ L-BFGS
▪ LGCD
Alex Gramfort Learning representations from neural signals
Optimization strategy
51
Block-coordinate descent:
[Grosse et al, 2007]
[Heide et al, 2015]
[Wohlberg, 2016]
[Jas et al, 2017]
[Dupré la Tour et al, 2018)
▪ D-step
▪ FFT
▪ ADMM + FFT
▪ ADMM + FFT
▪ L-BFGS (dual)
▪ PGD
[Kavukcuoglu et al, 2010]
[Chalasani et al, 2013]
[Bristow et al, 2013]
[Wohlberg, 2016]
[Jas et al, 2017]
[Dupré la Tour et al, 2018]
▪ Z-step
▪ GCD
▪ FISTA
▪ ADMM
▪ ADMM + FFT
▪ L-BFGS
▪ LGCD
Speed benchmarks
Speed benchmarks
Alex Gramfort Learning representations from neural signals
Learned atoms
53
Data:
~80	Hz
Alex Gramfort Learning representations from neural signals
Learned atoms
53
Data:
~80	Hz
CSC reveals CFC
Alex Gramfort Learning representations from neural signals
Learned atoms
53
Data:
How about if I
have many
channels?
~80	Hz
CSC reveals CFC
Alex Gramfort Learning representations from neural signals
From ICA to CSC
54
https://pypi.python.org/pypi/python-picard/0.1
Independent Component Analysis (ICA)
Alex Gramfort Learning representations from neural signals
From ICA to CSC
54
https://pypi.python.org/pypi/python-picard/0.1
Independent Component Analysis (ICA)
X S
Alex Gramfort Learning representations from neural signals
From ICA…
55
https://pypi.python.org/pypi/python-picard/0.1
X
=
A S
= + +…
a1 aks1 sk
+ +…
https://pierreablin.github.io/picard/auto_examples/plot_ica_eeg.html
https://www.martinos.org/mne/stable/auto_tutorials/plot_artifacts_correction_ica.html
Alex Gramfort Learning representations from neural signals
…
… to CSC
56
https://pypi.python.org/pypi/python-picard/0.1
X
=
+
u1 v1
⇤
z1
uk vk
⇤
zk
convolution
Alex Gramfort Learning representations from neural signals
…
⇤
Topography waveform temporal activations
… to CSC
56
https://pypi.python.org/pypi/python-picard/0.1
X
=
+
u1 v1
⇤
z1
uk vk
⇤
zk
convolution
Alex Gramfort Learning representations from neural signals
…
⇤
Topography waveform temporal activations
… to CSC
56
https://pypi.python.org/pypi/python-picard/0.1
X
=
+
u1 v1
⇤
z1
uk vk
⇤
zk
convolution
CSC allows to learn jointly
• topography (ie. localization)
• signal waveform
• when waveform occurs
Alex Gramfort Learning representations from neural signals
Multivariate CSC
57
[Multivariate Convolutional Sparse Coding for Electromagnetic Brain Signals, (2018),
T. Dupré laTour,  T. Moreau, M. Jas,A. Gramfort, Proc. NeurIPS Conf.]
Alex Gramfort Learning representations from neural signals
Multivariate CSC
57
[Multivariate Convolutional Sparse Coding for Electromagnetic Brain Signals, (2018),
T. Dupré laTour,  T. Moreau, M. Jas,A. Gramfort, Proc. NeurIPS Conf.]
Alex Gramfort Learning representations from neural signals
Multivariate CSC
57
[Multivariate Convolutional Sparse Coding for Electromagnetic Brain Signals, (2018),
T. Dupré laTour,  T. Moreau, M. Jas,A. Gramfort, Proc. NeurIPS Conf.]
Rank 1 constraint:
Alex Gramfort Learning representations from neural signals
CSC on MEG
58
https://pypi.python.org/pypi/python-picard/0.1
•MEG vectorview
•Median nerve stim.
[Multivariate Convolutional Sparse Coding for Electromagnetic Brain Signals, (2018),
T. Dupré laTour,  T. Moreau, M. Jas,A. Gramfort, Proc. NeurIPS Conf.]
Alex Gramfort Learning representations from neural signals
CSC on MEG
58
https://pypi.python.org/pypi/python-picard/0.1
•MEG vectorview
•Median nerve stim.
CSC reveals mu-
shaped waveforms
[Multivariate Convolutional Sparse Coding for Electromagnetic Brain Signals, (2018),
T. Dupré laTour,  T. Moreau, M. Jas,A. Gramfort, Proc. NeurIPS Conf.]
Alex Gramfort Learning representations from neural signals
CSC on MEG
58
https://pypi.python.org/pypi/python-picard/0.1
•MEG vectorview
•Median nerve stim.
See the frequency
harmonics
CSC reveals mu-
shaped waveforms
[Multivariate Convolutional Sparse Coding for Electromagnetic Brain Signals, (2018),
T. Dupré laTour,  T. Moreau, M. Jas,A. Gramfort, Proc. NeurIPS Conf.]
Alex Gramfort Learning representations from neural signals
CSC on MEG
59
Results on auditory task:
https://alphacsc.github.io
https://pypi.python.org/pypi/python-picard/0.1
https://alphacsc.github.io/auto_examples/multicsc/plot_sample_evoked_response.html
https://pypi.python.org/pypi/python-picard/0.1
https://alphacsc.github.io/auto_examples/multicsc/plot_sample_evoked_response.html
https://pypi.python.org/pypi/python-picard/0.1
https://alphacsc.github.io/auto_examples/multicsc/plot_sample_evoked_response.html
Use permutation
statistics to know if
atoms are condition
specific and if so when
Conclusion
• SoTA convolutional network for sleep
scoring on PSG data
• First deep architecture for event detection
on EEG data with SoTA performance
• CSC model: Fast solver and multivariate
• CSC comes with Python code
http://www.martinos.org/mne
MNE software for processing MEG and EEG data, A. Gramfort, M. Luessi, E. Larson, D. Engemann, D.
Strohmeier, C. Brodbeck, L. Parkkonen, M. Hämäläinen, Neuroimage 2013
http://www.martinos.org/mnehttp://www.martinos.org/mne
Harvard
U. Montreal
MNE developer in 2010
MNE developers in 2018
Berkeley
Paris
NYU
Cambridge Aalto
Ilmenau
Julich
Sheffield
U.Wash.
UCSF
Graz
Marseille
More than 80 people have contributed to MNE
>>> import mne
>>> raw = mne.io.read_raw_edf('SC4001E0-PSG.edf')
>>> annot = mne.read_annotations('SC4001EC-Hypnogram.edf')
>>> raw.set_annotations(annot)
>>> events, event_id = mne.events_from_annotations(raw)
>>> epochs = mne.Epochs(raw, events, event_id, tmin=0.,
tmax=30., baseline=None)
>>> epochs['Sleep stage W’].plot_psd(fmax=20., picks=[0, 1]))
https://github.com/mne-tools/mne-python/pull/5718
Working with EEG
sleep data in 7 lines
of Python code
https://swipe4ica.github.io/#/
https://github.com/SwipesForScience
Thanks !
GitHub : @agramfort Twitter : @agramfort
Support ERC SLAB,ANR THALAMEEG ANR-14-NEUC-0002-01
NIH R01 MH106174, DFG HA 2899/21-1.
http://alexandre.gramfort.netContact
S. Chambon,V.Thorey, P. J.Arnal, E. Mignot,A. Gramfort. (2018), DOSED: a deep learning
approach to detect multiple sleep micro-events in EEG signal,Arxiv 2500163
T. Dupré la Tour,  T. Moreau, M. Jas,A. Gramfort, Multivariate Convolutional Sparse
Coding for Electromagnetic Brain Signals, (2018), Proc. NeurIPS Conf.
M. Jas,T. Dupré la Tour, U. Simsekli,A. Gramfort, Learning the Morphology of Brain Signals
Using Alpha-Stable Convolutional Sparse Coding, (2017), Proc. NeurIPS Conf.
Tom Dupré laTour
Mainak Jas
Thomas Moreau
Umut Simsekli
Stanislas Chambon
ValentinThorey
Pierrick Arnal
Emmanuel Mignot
Joint work with:
S. Chambon, M. Galtier, P.Arnal, G.Wainrib, A. Gramfort (2018),A deep learning
architecture for temporal sleep stage classification using multivariate and multimodal
time series, IEEE Trans. Neural Systems and Rehabilitation Engineering

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MAIN Conf Talk: Learning representations from neural signals

  • 2. Alex Gramfort Learning representations from neural signals Neurons as current generators 2 Current Large cortical pyramidal cells organized in macro-assemblies with their dendrites normally oriented to the local cortical surface White matter Gray matter
  • 3. Alex Gramfort Learning representations from neural signals Neurons as current generators 2 Current Large cortical pyramidal cells organized in macro-assemblies with their dendrites normally oriented to the local cortical surface White matter Gray matter Q = I × d (10 to 100 nAm) with the equivalent current dipole (ECD) model B Magnetic Field Neural Current (post synaptic) Equivalent Current Dipole E Electric Field Neural Current (post synaptic) Equivalent Current Dipole
  • 4. Alex Gramfort Learning representations from neural signals Electro- & Magneto-encephalography 3 B Neural Current (post synaptic) Equivalent Current Dipole dB/dz MEG recordings First EEG recordings in 1929 by H. Berger Hôpital La Timone Marseille, France E Neural Current (post synaptic) Equivalent Current Dipole V EEG recordings
  • 5. Alex Gramfort Learning representations from neural signals Stereotaxic EEG (sEEG) 4 Intracranial electrodes; 5 to 15 contacts per electrode Around 10 electrodes are implanted Stereotaxic Implantation
  • 8. [T. Dupré laTour, L.Tallot, L. Grabot,V. Doyère,V. vanWassenhove,Y. Grenier,A. Gramfort, (2017) PLOS Computational biology] μ rhythm
  • 9. [T. Dupré laTour, L.Tallot, L. Grabot,V. Doyère,V. vanWassenhove,Y. Grenier,A. Gramfort, (2017) PLOS Computational biology] μ rhythm CFC: High frequency bursts coupled with slow waves
  • 10. [T. Dupré laTour, L.Tallot, L. Grabot,V. Doyère,V. vanWassenhove,Y. Grenier,A. Gramfort, (2017) PLOS Computational biology] μ rhythm CFC: High frequency bursts coupled with slow waves Neural signals exhibit diverse and complex morphologies
  • 11. Alex Gramfort Learning representations from neural signals “Textbook” brain rythms 6 Gamma (> 25 Hz) Beta (12-25 Hz) Alpha (8-12 Hz) Theta (4-8 Hz) Delta (1-4 Hz)
  • 12. Alex Gramfort Learning representations from neural signals Fourier Fallacy [Jasper 48] 7 Power Spectra:Waveform:Topography:
  • 13. Alex Gramfort Learning representations from neural signals Fourier Fallacy [Jasper 48] 7 «Even though it may be possible to analyze the complex forms of brain waves into a number of different sine-wave frequencies, this may lead only to what might be termed a “Fourier fallacy”, if one assumes ad hoc that all of the necessary frequencies actually occur as periodic phenomena in cell groups within the brain. » Jasper, 1948 Power Spectra:Waveform:Topography:
  • 14. Alex Gramfort Learning representations from neural signals Fourier Fallacy [Jasper 48] 7 «Even though it may be possible to analyze the complex forms of brain waves into a number of different sine-wave frequencies, this may lead only to what might be termed a “Fourier fallacy”, if one assumes ad hoc that all of the necessary frequencies actually occur as periodic phenomena in cell groups within the brain. » Jasper, 1948 Harmonics Power Spectra:Waveform:Topography:
  • 15. Alex Gramfort Learning representations from neural signals Outline 8 S. Chambon,V.Thorey, P. J.Arnal, E. Mignot,A. Gramfort. (2018), DOSED: a deep learning approach to detect multiple sleep micro-events in EEG signal,Arxiv 2500163 S. Chambon, M. Galtier, P.Arnal, G.Wainrib, A. Gramfort (2018),A deep learning architecture for temporal sleep stage classification using multivariate and multimodal time series, IEEE Trans. Neural Systems and Rehabilitation Engineering T. Dupré la Tour,  T. Moreau, M. Jas,A. Gramfort (2018), Multivariate Convolutional Sparse Coding for Electromagnetic Brain Signals, Proc. NeurIPS Conf. M. Jas,T. Dupré la Tour, U. Simsekli,A. Gramfort (2017), Learning the Morphology of Brain Signals Using Alpha-Stable Convolutional Sparse Coding, Proc. NeurIPS Conf. Polysomnography exam: I Electroencephalography (EEG) I Electrooculography (EOG) I Electromyography (EMG) I · · · Preliminary exam in sleep studies: I sleep disorders I psychiatric disorders... Polysomnographie “Deep” supervised learning on sleep EEG data: Unsupervised convolutional sparse coding:
  • 16. Deep supervised learning on sleep EEG data 1 Spindle K-complex
  • 17. Alex Gramfort Learning representations from neural signals Polysomnography (PSG) • Clinical exam • Electrophysiological signals 10 Electro-oculography (EOG) Electro-encephalography (EEG) Electro-myography (EMG)
  • 18. Alex Gramfort Learning representations from neural signals Polysomnography (PSG) • Clinical exam • Electrophysiological signals 10 Electro-oculography (EOG) Electro-encephalography (EEG) Electro-myography (EMG) Routinely annotated by sleep experts
  • 19. Alex Gramfort Learning representations from neural signals 2 types of annotations Hypnogram
 of sleep stages Micro-events: Spindles, K-complex etc. 11
  • 20. Alex Gramfort Learning representations from neural signals 2 types of annotations Hypnogram
 of sleep stages Micro-events: Spindles, K-complex etc. 11 Classification problem
  • 21. Alex Gramfort Learning representations from neural signals 2 types of annotations Hypnogram
 of sleep stages Micro-events: Spindles, K-complex etc. 11 Classification problem Joint detection and classification problem
  • 23. Alex Gramfort Learning representations from neural signals Objective 13 PSG data
  • 24. Alex Gramfort Learning representations from neural signals Objective 13 x 2 X PSG data
  • 25. Alex Gramfort Learning representations from neural signals Objective 13 Learn: ˆf : X ! Y Y = {Awake, REM, Stage 1, Stage 2, etc.} x 2 X PSG data
  • 26. Alex Gramfort Learning representations from neural signals Objective 13 Learn: ˆf : X ! Y Y = {Awake, REM, Stage 1, Stage 2, etc.} x 2 X PSG data Multiclass prediction problem Input is multiple time series
  • 27. Alex Gramfort Learning representations from neural signals and many more…. An old yet timely problem 14 C. Berthomier, X. Drouot, M. Herman-Stoïca, et al. ,“Automatic analysis of single-channel sleep EEG: validation in healthy individuals.,” Sleep, vol. 30, no. 11, pp. 1587–1595, 2007. O.Tsinalis, P. M. Matthews, andY. Guo,“Automatic Sleep Stage Scoring Using Time-Frequency Analysis and Stacked Sparse Autoencoders,” Annals of Biomedical Engineering, vol. 44, no. 5, pp. 1587–1597, 2016. J. B. Stephansen, A.Ambati, E. B. Leary, et al.,“The use of neural networks in the analysis of sleep stages and the diagnosis of narcolepsy,” CoRR, vol. abs/1710.02094, 2017. A.Vilamala, K. H. Madsen, and L. K. Hansen,“Deep convolutional neural networks for interpretable analysis of EEG sleep stage scoring,” 2017 IEEE Workshop on Machine Learning for Signal Processing (MLSP) S.Biswal, J.Kulas, H.Sun, B.Goparaju, M.B.Westover, M.T.Bianchi and J. Sun,“SLEEPNET: automated sleep staging system via deep learning,” arXiv:1707.08262, 2017. H. Dong,A. Supratak,W. Pan, C.Wu, P. M. Matthews, andY. Guo,“Mixed Neural Network Approach for Temporal Sleep Stage Classification,” arXiv:1610.06421v1, vol. 1, 2016. O.Tsinalis, P.M. Matthews,Y. Guo and S.Zafeiriou,“Automatic Sleep Stage Scoring with Single-Channel EEG Using Convolutional Neural Networks,” arXiv:1610.01683, pp. 1–10, 2016. A. Supratak, H. Dong, C.Wu, andY. Guo,“Deepsleepnet: a model for automatic sleep stage scoring based on raw single-channel EEG,” IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2017. T. Lajnef, S. Chaibi, P. Ruby, et al. ,“Learning Machines and Sleeping Brains:Automatic Sleep Stage Classification using Decision-Tree Multi-Class SupportVector Machines,” Journal of Neuroscience Methods, 2015.
  • 28. Alex Gramfort Learning representations from neural signals and many more…. An old yet timely problem 14 C. Berthomier, X. Drouot, M. Herman-Stoïca, et al. ,“Automatic analysis of single-channel sleep EEG: validation in healthy individuals.,” Sleep, vol. 30, no. 11, pp. 1587–1595, 2007. O.Tsinalis, P. M. Matthews, andY. Guo,“Automatic Sleep Stage Scoring Using Time-Frequency Analysis and Stacked Sparse Autoencoders,” Annals of Biomedical Engineering, vol. 44, no. 5, pp. 1587–1597, 2016. J. B. Stephansen, A.Ambati, E. B. Leary, et al.,“The use of neural networks in the analysis of sleep stages and the diagnosis of narcolepsy,” CoRR, vol. abs/1710.02094, 2017. A.Vilamala, K. H. Madsen, and L. K. Hansen,“Deep convolutional neural networks for interpretable analysis of EEG sleep stage scoring,” 2017 IEEE Workshop on Machine Learning for Signal Processing (MLSP) S.Biswal, J.Kulas, H.Sun, B.Goparaju, M.B.Westover, M.T.Bianchi and J. Sun,“SLEEPNET: automated sleep staging system via deep learning,” arXiv:1707.08262, 2017. H. Dong,A. Supratak,W. Pan, C.Wu, P. M. Matthews, andY. Guo,“Mixed Neural Network Approach for Temporal Sleep Stage Classification,” arXiv:1610.06421v1, vol. 1, 2016. O.Tsinalis, P.M. Matthews,Y. Guo and S.Zafeiriou,“Automatic Sleep Stage Scoring with Single-Channel EEG Using Convolutional Neural Networks,” arXiv:1610.01683, pp. 1–10, 2016. A. Supratak, H. Dong, C.Wu, andY. Guo,“Deepsleepnet: a model for automatic sleep stage scoring based on raw single-channel EEG,” IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2017. T. Lajnef, S. Chaibi, P. Ruby, et al. ,“Learning Machines and Sleeping Brains:Automatic Sleep Stage Classification using Decision-Tree Multi-Class SupportVector Machines,” Journal of Neuroscience Methods, 2015. To be compared
  • 29. Alex Gramfort Learning representations from neural signals and many more…. An old yet timely problem 14 Obj: learn from raw multimodal and multivariate signals C. Berthomier, X. Drouot, M. Herman-Stoïca, et al. ,“Automatic analysis of single-channel sleep EEG: validation in healthy individuals.,” Sleep, vol. 30, no. 11, pp. 1587–1595, 2007. O.Tsinalis, P. M. Matthews, andY. Guo,“Automatic Sleep Stage Scoring Using Time-Frequency Analysis and Stacked Sparse Autoencoders,” Annals of Biomedical Engineering, vol. 44, no. 5, pp. 1587–1597, 2016. J. B. Stephansen, A.Ambati, E. B. Leary, et al.,“The use of neural networks in the analysis of sleep stages and the diagnosis of narcolepsy,” CoRR, vol. abs/1710.02094, 2017. A.Vilamala, K. H. Madsen, and L. K. Hansen,“Deep convolutional neural networks for interpretable analysis of EEG sleep stage scoring,” 2017 IEEE Workshop on Machine Learning for Signal Processing (MLSP) S.Biswal, J.Kulas, H.Sun, B.Goparaju, M.B.Westover, M.T.Bianchi and J. Sun,“SLEEPNET: automated sleep staging system via deep learning,” arXiv:1707.08262, 2017. H. Dong,A. Supratak,W. Pan, C.Wu, P. M. Matthews, andY. Guo,“Mixed Neural Network Approach for Temporal Sleep Stage Classification,” arXiv:1610.06421v1, vol. 1, 2016. O.Tsinalis, P.M. Matthews,Y. Guo and S.Zafeiriou,“Automatic Sleep Stage Scoring with Single-Channel EEG Using Convolutional Neural Networks,” arXiv:1610.01683, pp. 1–10, 2016. A. Supratak, H. Dong, C.Wu, andY. Guo,“Deepsleepnet: a model for automatic sleep stage scoring based on raw single-channel EEG,” IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2017. T. Lajnef, S. Chaibi, P. Ruby, et al. ,“Learning Machines and Sleeping Brains:Automatic Sleep Stage Classification using Decision-Tree Multi-Class SupportVector Machines,” Journal of Neuroscience Methods, 2015. To be compared
  • 30. Alex Gramfort Learning representations from neural signals Proposed approach Features • Convolutional Neural Net (CNN): Frequency content Spatial context • Multivariate signals: spatial filtering (like ICA would do) • Multimodal inputs: different pipelines for EEG, EOG and EMG Temporal context • Concatenate features of neighboring samples [A deep learning architecture for temporal sleep stage classification using multivariate and multimodal time series. S. Chambon, M. N. Galtier, P. J.Arnal, G.Wainrib,A. Gramfort. IEEE TSRNE 2018] 15
  • 31. Alex Gramfort Learning representations from neural signals Problem formulation 16 ˆf 2 argminf2F Ex,y2X⇥Y [`(y, f(x))] Risk minimization:
  • 32. Alex Gramfort Learning representations from neural signals Problem formulation 16 ˆf 2 argminf2F Ex,y2X⇥Y [`(y, f(x))] Risk minimization: F• : a class of models (neural networks architecture).
  • 33. Alex Gramfort Learning representations from neural signals Problem formulation 16 ˆf 2 argminf2F Ex,y2X⇥Y [`(y, f(x))] Risk minimization: F• : a class of models (neural networks architecture). `• : loss.We use the categorical cross-entropy. • Minimized on a training set using backpropagation and online stochastic gradient descent.
  • 34. shape = (C, T) Spatial Filtering shape = (C’, T) Spatial Filtering EEG/EOG EMG Input Conv/Relu/MP Softmax Conv/Relu/MP 𝜙C 𝜓 𝜙 𝜙T
  • 35. shape = (C, T) Spatial Filtering shape = (C’, T) Spatial Filtering EEG/EOG EMG Input Conv/Relu/MP Softmax Conv/Relu/MP 𝜙C 𝜓 𝜙 𝜙T shape = (C, T) Spatial Filtering shape = (C’, T) Spatial Filtering EEG/EOG EMG Input Conv/Relu/MP Softmax Conv/Relu/MP 𝜙C 𝜓 𝜙 𝜙T
  • 36. shape = (C, T) Spatial Filtering shape = (C’, T) Spatial Filtering EEG/EOG EMG Input Conv/Relu/MP Softmax Conv/Relu/MP 𝜙C 𝜓 𝜙 𝜙T shape = (C, T) Spatial Filtering shape = (C’, T) Spatial Filtering EEG/EOG EMG Input Conv/Relu/MP Softmax Conv/Relu/MP 𝜙C 𝜓 𝜙 𝜙T
  • 37. shape = (C, T) Spatial Filtering shape = (C’, T) Spatial Filtering EEG/EOG EMG Input Conv/Relu/MP Softmax Conv/Relu/MP 𝜙C 𝜓 𝜙 𝜙T shape = (C, T) Spatial Filtering shape = (C’, T) Spatial Filtering EEG/EOG EMG Input Conv/Relu/MP Softmax Conv/Relu/MP 𝜙C 𝜓 𝜙 𝜙T shape = (C, T) Spatial Filtering shape = (C’, T) Spatial Filtering EEG/EOG EMG Input Conv/Relu/MP Softmax Conv/Relu/MP 𝜙C 𝜓 𝜙 𝜙T
  • 38. shape = (C, T) Spatial Filtering shape = (C’, T) Spatial Filtering EEG/EOG EMG Input Conv/Relu/MP Softmax Conv/Relu/MP 𝜙C 𝜓 𝜙 𝜙T
  • 39. shape = (C, T) Spatial Filtering shape = (C’, T) Spatial Filtering EEG/EOG EMG Input Conv/Relu/MP Softmax Conv/Relu/MP 𝜙C 𝜓 𝜙 𝜙T Block 1 Conv, ReLU, Max Pooling Input Block 2
  • 40. Alex Gramfort Learning representations from neural signals Model parameters 23
  • 41. Alex Gramfort Learning representations from neural signals Model parameters 23 Spatial filtering
  • 42. Alex Gramfort Learning representations from neural signals Model parameters 23 Spatial filtering Conv. layer 1
  • 43. Alex Gramfort Learning representations from neural signals Model parameters 23 Spatial filtering Conv. layer 1 Conv. layer 2
  • 45. zt k zt zt+k Time (s) 𝜙𝜙 𝜙 𝜓 Sequence of inputsEEGChannels F4 F3 C3 C4 O1 O2 -60 -30 0 30 60 90 yt
  • 46. zt k zt zt+k Time (s) 𝜙𝜙 𝜙 𝜓 Sequence of inputsEEGChannels F4 F3 C3 C4 O1 O2 -60 -30 0 30 60 90 yt We pool the representations from neighboring windows
  • 48. Alex Gramfort Learning representations from neural signals Experimental setup • Data • MASS - session 3: O’Reilly et al. 2014 • http://www.ceams-carsm.ca/en/MASS • 61 records, ~10h / record • Total number of samples about 60,000 (like for MNIST) • Preprocessing • lowpass filtering (30Hz) • downsampling 128Hz 27
  • 49. Alex Gramfort Learning representations from neural signals Experimental setup • Cross validation • 5 splits • 41 records for training, 10 for validation, 10 for testing • Baselines • Gradient boosting: Hand crafted features (mean, variance… relative power in frequency bands) [Lajnev et al. 2015] • [Tsinalis et al. 2016]: deep convolutional network • [Supratak et al. 2017]: deep convolutional network processing low and high frequency contents specifically 28
  • 50. Alex Gramfort Learning representations from neural signals Influence of spatial context 29
  • 52. Influence of temporal context 30 • Temporal context helps • But less when using more channels
  • 53. Alex Gramfort Learning representations from neural signals Performance vs SoTA 31 Performance: Computational efficiency:
  • 54. Alex Gramfort Learning representations from neural signals Performance vs SoTA 31 Performance: Computational efficiency: • Networks outperform hand crafted features with gradient boosting • Combining all modalities helps (multivariate) • SoTA is obtained with less parameters (fast)
  • 55. Alex Gramfort Learning representations from neural signals “Opening” the black box 32 Confusion matrix: N1 is hard
  • 56. Alex Gramfort Learning representations from neural signals “Opening” the black box 32 Confusion matrix: N1 is hard “Hiding” frequencies from the network: network has learnt scoring rules
  • 57. Start time End time Type Joint detection and classification of micro-events [A deep learning architecture to detect events in EEG signals during sleep. S. Chambon,V.Thorey, P. J.Arnal, E. Mignot,A. Gramfort. MLSP 2018] [DOSED: a deep learning approach to detect multiple sleep micro-events in EEG signal,. S. Chambon,V.Thorey, P. J.Arnal, E. Mignot,A. Gramfort. Arxiv 2500163]
  • 58. Start time End time Type Joint detection and classification of micro-events Objective: Predict what and when at the same time [A deep learning architecture to detect events in EEG signals during sleep. S. Chambon,V.Thorey, P. J.Arnal, E. Mignot,A. Gramfort. MLSP 2018] [DOSED: a deep learning approach to detect multiple sleep micro-events in EEG signal,. S. Chambon,V.Thorey, P. J.Arnal, E. Mignot,A. Gramfort. Arxiv 2500163]
  • 59. Alex Gramfort Learning representations from neural signals Spindles K-complex Spindles and K-complexes in N2 stage • Different types, durations, scales • Associated to certain sleep stages and sleep disorders Micro-events 34 Why is it hard? Why should you care?
  • 60. Alex Gramfort Learning representations from neural signals State of the art • Signal processing: • Band-pass filtering + thresholding • Decomposition into components • Shallow learning algorithms: • Clustering • Binary classifier 35 [Parekh et al. 2017, Lajnef et al. 2017] [Ray et al. 2015,Wamsley et al. 2012,Wendt et al. 2012, Mölle et al. 2011, Nir et al. 2011, Ferrarelli et al. 2007] [Patti et al. 2017] [Patti et al. 2015, Lachner-Piza et al. 2018] None of these works use deep learning
  • 61. Alex Gramfort Learning representations from neural signals DOSED algorithm Inspired by: YOLO and SSD 1. Predict: type, start & end 2. Allows for multiple types of events 3. Detection and classification in one pass 4. Convolutional network 36 [Redmon et al. 2016, Liu et al. 2015]
  • 62. Alex Gramfort Learning representations from neural signals Event detector 𝜓loc : conv. layerInput 𝜙: CNN 𝜓clf : conv. layer Setup Model Default events 37
  • 63. Alex Gramfort Learning representations from neural signals d1 d2 dNd Loss: localization + classification !38
  • 64. Alex Gramfort Learning representations from neural signals d1 d2 dNd Default events overlapping with true events Loss: localization + classification !39
  • 65. Alex Gramfort Learning representations from neural signals d1 d2 dNd Remaining default events Loss: localization + classification !40 Default events overlapping with true events
  • 66. Alex Gramfort Learning representations from neural signals Evaluation •By event metrics
 
 •Based on Intersection over Union (IoU)
 •Precision, Recall, F1 Predicted event True event 41 [Warby et al. 2014] IoU < 𝜕 => False positive IoU > 𝜕 => True positive
  • 67. Alex Gramfort Learning representations from neural signals 3 datasets SS2
 [O’Reilly et al. 2014] SSC
 [Andlauer et al. 2013] WSC [Young et al. 2008] # Subjects 19 26 30 Age 23.6 ± 3.7 52.2 ± 14.3 65.2 ± 8.2 Aplit
 (train, val, test) 10, 5, 4 15, 5, 6 19, 5, 6 Events spindles
 K-complexes spindles spindles 42
  • 69. Alex Gramfort Learning representations from neural signals Illustration 44 True event Predicted event
  • 70. Alex Gramfort Learning representations from neural signals Illustration 44 True event Predicted event
  • 71. Alex Gramfort Learning representations from neural signals Joint detection 45 Joint detection does not deteriorate performance
  • 72. Convolutional Sparse Coding (CSC) for learning the morphology of neural signals 2 Code: https://alphacsc.github.io Multivariate Convolutional Sparse Coding for Electromagnetic Brain Signals, (2018), T. Dupré laTour, T. Moreau, M. Jas,A. Gramfort, Proc. NeurIPS Conf. Learning the Morphology of Brain Signals Using Alpha-Stable Convolutional Sparse Coding, (2017), M. Jas,T. Dupré laTour, U. Simsekli,A. Gramfort, Proc. NeurIPS Conf.
  • 73. Alex Gramfort Learning representations from neural signals Signal representations ▪Sparse representations: wavelet basis ▪Sparse coding / dictionary learning ▪Shift-invariant representations ▪In neurophysiology: ▪ Matching of time-invariant filters (MOTIF) ▪ Multivariate orthogonal matching pursuit ▪ Matching pursuit and heuristics ▪ Sliding window machine ▪ Adaptive waveform learning 47 [Morlet 70’, Meyer 80’, Mallat 90’ etc.] [Olshausen and Field, 1996, Elad and Aharon, 2006] [Lewicki and Sejnowski, 1999, Grosse et al, 2007] [Jost et al, 2006] [Gips et al, 2017] [Hitziger et al, 2017] [Barthélemy et al, 2012] [Brokmeier and Principe, 2016]
  • 74. Alex Gramfort Learning representations from neural signals Convolutional sparse coding 48 [Grosse et al, 2007]
  • 75. Alex Gramfort Learning representations from neural signals Convolutional sparse coding 49 [Grosse et al, 2007]
  • 76. Alex Gramfort Learning representations from neural signals Convolutional sparse coding 50 [Grosse et al, 2007]
  • 77. Alex Gramfort Learning representations from neural signals Optimization strategy 51 Block-coordinate descent:
  • 78. Alex Gramfort Learning representations from neural signals Optimization strategy 51 Block-coordinate descent: [Kavukcuoglu et al, 2010] [Chalasani et al, 2013] [Bristow et al, 2013] [Wohlberg, 2016] [Jas et al, 2017] [Dupré la Tour et al, 2018] ▪ Z-step ▪ GCD ▪ FISTA ▪ ADMM ▪ ADMM + FFT ▪ L-BFGS ▪ LGCD
  • 79. Alex Gramfort Learning representations from neural signals Optimization strategy 51 Block-coordinate descent: [Grosse et al, 2007] [Heide et al, 2015] [Wohlberg, 2016] [Jas et al, 2017] [Dupré la Tour et al, 2018) ▪ D-step ▪ FFT ▪ ADMM + FFT ▪ ADMM + FFT ▪ L-BFGS (dual) ▪ PGD [Kavukcuoglu et al, 2010] [Chalasani et al, 2013] [Bristow et al, 2013] [Wohlberg, 2016] [Jas et al, 2017] [Dupré la Tour et al, 2018] ▪ Z-step ▪ GCD ▪ FISTA ▪ ADMM ▪ ADMM + FFT ▪ L-BFGS ▪ LGCD
  • 82. Alex Gramfort Learning representations from neural signals Learned atoms 53 Data: ~80 Hz
  • 83. Alex Gramfort Learning representations from neural signals Learned atoms 53 Data: ~80 Hz CSC reveals CFC
  • 84. Alex Gramfort Learning representations from neural signals Learned atoms 53 Data: How about if I have many channels? ~80 Hz CSC reveals CFC
  • 85. Alex Gramfort Learning representations from neural signals From ICA to CSC 54 https://pypi.python.org/pypi/python-picard/0.1 Independent Component Analysis (ICA)
  • 86. Alex Gramfort Learning representations from neural signals From ICA to CSC 54 https://pypi.python.org/pypi/python-picard/0.1 Independent Component Analysis (ICA) X S
  • 87. Alex Gramfort Learning representations from neural signals From ICA… 55 https://pypi.python.org/pypi/python-picard/0.1 X = A S = + +… a1 aks1 sk + +… https://pierreablin.github.io/picard/auto_examples/plot_ica_eeg.html https://www.martinos.org/mne/stable/auto_tutorials/plot_artifacts_correction_ica.html
  • 88. Alex Gramfort Learning representations from neural signals … … to CSC 56 https://pypi.python.org/pypi/python-picard/0.1 X = + u1 v1 ⇤ z1 uk vk ⇤ zk convolution
  • 89. Alex Gramfort Learning representations from neural signals … ⇤ Topography waveform temporal activations … to CSC 56 https://pypi.python.org/pypi/python-picard/0.1 X = + u1 v1 ⇤ z1 uk vk ⇤ zk convolution
  • 90. Alex Gramfort Learning representations from neural signals … ⇤ Topography waveform temporal activations … to CSC 56 https://pypi.python.org/pypi/python-picard/0.1 X = + u1 v1 ⇤ z1 uk vk ⇤ zk convolution CSC allows to learn jointly • topography (ie. localization) • signal waveform • when waveform occurs
  • 91. Alex Gramfort Learning representations from neural signals Multivariate CSC 57 [Multivariate Convolutional Sparse Coding for Electromagnetic Brain Signals, (2018), T. Dupré laTour,  T. Moreau, M. Jas,A. Gramfort, Proc. NeurIPS Conf.]
  • 92. Alex Gramfort Learning representations from neural signals Multivariate CSC 57 [Multivariate Convolutional Sparse Coding for Electromagnetic Brain Signals, (2018), T. Dupré laTour,  T. Moreau, M. Jas,A. Gramfort, Proc. NeurIPS Conf.]
  • 93. Alex Gramfort Learning representations from neural signals Multivariate CSC 57 [Multivariate Convolutional Sparse Coding for Electromagnetic Brain Signals, (2018), T. Dupré laTour,  T. Moreau, M. Jas,A. Gramfort, Proc. NeurIPS Conf.] Rank 1 constraint:
  • 94. Alex Gramfort Learning representations from neural signals CSC on MEG 58 https://pypi.python.org/pypi/python-picard/0.1 •MEG vectorview •Median nerve stim. [Multivariate Convolutional Sparse Coding for Electromagnetic Brain Signals, (2018), T. Dupré laTour,  T. Moreau, M. Jas,A. Gramfort, Proc. NeurIPS Conf.]
  • 95. Alex Gramfort Learning representations from neural signals CSC on MEG 58 https://pypi.python.org/pypi/python-picard/0.1 •MEG vectorview •Median nerve stim. CSC reveals mu- shaped waveforms [Multivariate Convolutional Sparse Coding for Electromagnetic Brain Signals, (2018), T. Dupré laTour,  T. Moreau, M. Jas,A. Gramfort, Proc. NeurIPS Conf.]
  • 96. Alex Gramfort Learning representations from neural signals CSC on MEG 58 https://pypi.python.org/pypi/python-picard/0.1 •MEG vectorview •Median nerve stim. See the frequency harmonics CSC reveals mu- shaped waveforms [Multivariate Convolutional Sparse Coding for Electromagnetic Brain Signals, (2018), T. Dupré laTour,  T. Moreau, M. Jas,A. Gramfort, Proc. NeurIPS Conf.]
  • 97. Alex Gramfort Learning representations from neural signals CSC on MEG 59 Results on auditory task:
  • 102. Conclusion • SoTA convolutional network for sleep scoring on PSG data • First deep architecture for event detection on EEG data with SoTA performance • CSC model: Fast solver and multivariate • CSC comes with Python code
  • 103. http://www.martinos.org/mne MNE software for processing MEG and EEG data, A. Gramfort, M. Luessi, E. Larson, D. Engemann, D. Strohmeier, C. Brodbeck, L. Parkkonen, M. Hämäläinen, Neuroimage 2013
  • 104. http://www.martinos.org/mnehttp://www.martinos.org/mne Harvard U. Montreal MNE developer in 2010 MNE developers in 2018 Berkeley Paris NYU Cambridge Aalto Ilmenau Julich Sheffield U.Wash. UCSF Graz Marseille More than 80 people have contributed to MNE
  • 105. >>> import mne >>> raw = mne.io.read_raw_edf('SC4001E0-PSG.edf') >>> annot = mne.read_annotations('SC4001EC-Hypnogram.edf') >>> raw.set_annotations(annot) >>> events, event_id = mne.events_from_annotations(raw) >>> epochs = mne.Epochs(raw, events, event_id, tmin=0., tmax=30., baseline=None) >>> epochs['Sleep stage W’].plot_psd(fmax=20., picks=[0, 1])) https://github.com/mne-tools/mne-python/pull/5718 Working with EEG sleep data in 7 lines of Python code
  • 107. Thanks ! GitHub : @agramfort Twitter : @agramfort Support ERC SLAB,ANR THALAMEEG ANR-14-NEUC-0002-01 NIH R01 MH106174, DFG HA 2899/21-1. http://alexandre.gramfort.netContact S. Chambon,V.Thorey, P. J.Arnal, E. Mignot,A. Gramfort. (2018), DOSED: a deep learning approach to detect multiple sleep micro-events in EEG signal,Arxiv 2500163 T. Dupré la Tour,  T. Moreau, M. Jas,A. Gramfort, Multivariate Convolutional Sparse Coding for Electromagnetic Brain Signals, (2018), Proc. NeurIPS Conf. M. Jas,T. Dupré la Tour, U. Simsekli,A. Gramfort, Learning the Morphology of Brain Signals Using Alpha-Stable Convolutional Sparse Coding, (2017), Proc. NeurIPS Conf. Tom Dupré laTour Mainak Jas Thomas Moreau Umut Simsekli Stanislas Chambon ValentinThorey Pierrick Arnal Emmanuel Mignot Joint work with: S. Chambon, M. Galtier, P.Arnal, G.Wainrib, A. Gramfort (2018),A deep learning architecture for temporal sleep stage classification using multivariate and multimodal time series, IEEE Trans. Neural Systems and Rehabilitation Engineering