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Introduction and motivation
Comparitive investigation:
Predictive performance of measures of synchronization
Statistical validation of seizure predictions:
The method of measure profile surrogates
Summary and outlook
Predictability of epileptic seizures- Content -
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~ 1 % of world population suffers from epilepsy
~ 22 % cannot be treated sufficiently
~ 70 % can be treated with antiepileptic drugs
~ 8 % might profit from epilepsy surgery
Exact localization of seizure generating area
Delineation from functionally relevant areas
Aim: Tailored resection of epileptic focus
Predictability of epileptic seizures- Introduction: Epilepsy -
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Intracranially implanted electrodes
TBARTBPR TBAL
TBPL
TL TR
FLRFPR
FPLFLL
TLLTLR
RL
RL
RL
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EEG containing onset of a seizure (preictal and ictal)
L
R
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EEG in the seizure-free period (interictal)
L
R
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Predictability of epileptic seizures- Motivation I -
Open questions:
Does a preictal state exist?
Do characterizing measures allow a reliable detection of this state?
Goals / Perspectives:
Increasing the patient‘s quality of life
Therapy on demand (Medication, Prevention)
Understanding seizure generating processes
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Predictability of epileptic seizures- Motivation II -
State of the art:
Reports on the existence of a preictal state, mainly based on univariate measures
Gradual shift towards the application of bivariate measures
Little experience with continuous multi-day recordings
No comparison of different characterizing measures
Mostly no statistical validation of results
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Predictability of epileptic seizures- Motivation III -
Why bivariate measures?
Synchronization phenomena key feature for establishing the communication between different regions of the brain
Epileptic seizure: Abnormal synchronization of neuronal ensembles
First promising results on short datasets:“Drop of synchronization” before epileptic seizures *
* Mormann, Kreuz, Andrzejak et al., Epilepsy Research, 2003; Mormann, Andrzejak, Kreuz et al., Phys. Rev. E, 2003
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I. Continuous EEG – multichannel recordings
II. Calculation of a characterizing measure
III. Investigation of suitability for prediction by means of a seizure prediction statistics
- Sensitivity Performance
- Specificity
IV. Estimation of statistical significance
Predictability of epileptic seizures- Procedure -
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1 2 3 4 5 6 7 80
0.5
1M
-303
x (t
)
20 40 60 80 100 120 140 160
-303
y (t
)
t [s]
Predictability of epileptic seizures- Moving window analysis -
Window
Chan. 1
Chan. 2
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1 2 3 4 5 6 7 80
0.5
1M
-303
x (t
)
20 40 60 80 100 120 140 160
-303
y (t
)
t [s]
Predictability of epileptic seizures- Moving window analysis -
Window
Chan. 1
Chan. 2
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1 2 3 4 5 6 7 80
0.5
1M
-303
x (t
)
20 40 60 80 100 120 140 160
-303
y (t
)
t [s]
Predictability of epileptic seizures- Moving window analysis -
Window
Chan. 1
Chan. 2
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1 2 3 4 5 6 7 80
0.5
1M
-303
x (t
)
20 40 60 80 100 120 140 160
-303
y (t
)
t [s]
Predictability of epileptic seizures- Moving window analysis -
Window
…
Chan. 1
Chan. 2
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1 2 3 4 50
0.2
0.4
0.6
0.8
1
Zeit [Tage]
a)
RH
sensitivenot
sensitivenot
specific specific
For this channel combination:
Reliable seperation preictal interictal impossible !
Predictability of epileptic seizures - Example: Drop of synchronization as a predictor -
Time [Days]
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1 2 3 4 50
0.2
0.4
0.6
0.8
1
Zeit [Tage]
a)
RH
Predictability of epileptic seizures- Example: Drop of synchronization as a predictor -
Selection of best channel combination :
Clearly improved seperation preictal interictal
Significant ? Seizure times surrogates
Time [Days]
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Introduction and motivation
Comparitive investigation:
Predictive performance of measures of synchronization
Statistical validation of seizure predictions:
The method of measure profile surrogates
Summary and outlook
Predictability of epileptic seizures- Content -
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I. Continuous EEG – multichannel recordings
II. Calculation of a characterizing measure
III. Investigation of suitability for prediction by means of a seizure prediction statistics
- Sensitivity Performance
- Specificity
IV. Estimation of statistical significance
Predictability of epileptic seizures- Procedure -
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10
15
3
6
17
1
6
5
3
Anfälle
Zeit [Std.]
Pa
tien
t
30 60 90 120 150 180
A
B
C
D
E
F
G
H
I
I. DatabaseSeizures
Time [h]
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I. Continuous EEG – multichannel recordings
II. Calculation of a characterizing measure
III. Investigation of suitability for prediction by means of a seizure prediction statistics
- Sensitivity Performance
- Specificity
IV. Estimation of statistical significance
Predictability of epileptic seizures- Procedure -
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• Cross Correlation Cmax
• Mutual Information I
• Indices of phase synchronization
based on
and using
• Nonlinear interdependencies Ss and Hs
• Event synchronization Q
Synchronization Directionality
• Nonlinear interdependencies Sa and Ha
• Delay asymmetry q
- Shannon entropy (se)
- Conditional probabilty (cp)- Circular variance (cv)
- Hilbert phase (H)
- Wavelet phase (W)Wcv
Hcv
Wcp
Hcp
Wse
Hse , , , , ,
II. Bivariate measures- Overview -
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II. Bivariate measures- Cross correlation and mutual information -
1.0
0.5
0.0
Cmax I
* *
1.0
0.5
0.0
Cmax I
* *1.0
0.5
0.0
Cmax I
**
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0 2
-1 -0.5 0 0.5 1-1
-0.5
0
0.5
1
0
/2
3/2
0 2
-1 -0.5 0 0.5 1-1
-0.5
0
0.5
1
0
/2
3/2
0 2
-1 -0.5 0 0.5 1-1
-0.5
0
0.5
1
0
/2
3/2
II. Bivariate measures- Phase synchronization -
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II. Bivariate measures- Nonlinear interdependencies -
No coupling:
X
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II. Bivariate measures- Nonlinear interdependencies -
Strong coupling:
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1 2-4
0
4
Kanal 2
Kanal 1
0
25
Q*
q*
Zeit [s]
II. Bivariate measures- Event synchronization and Delay
asymmetry I -
Time [s]
Chan. 1
Chan. 2
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I. Continuous EEG – multichannel recordings
II. Calculation of a characterizing measure
III. Investigation of suitability for prediction by means of a seizure prediction statistics
- Sensitivity Performance
- Specificity
IV. Estimation of statistical significance
Predictability of epileptic seizures- Procedure -
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III. Seizure prediction statistics - Steps of analysis -
Measure profiles of all neighboring channel combinations
Statistical approach:
Comparison of preictal and interictal
amplitude distributions
Measure of discrimination: Area below the
Receiver-Operating-Characteristics (ROC) - Curve
Mormann, Kreuz, Rieke et al., Clin Neurophysiol 2005
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-4 -2 0 2 40
0.01
0.02
0.03
0.04
0 0.5 10
0.5
1
Sen
sitiv
ität
1-Spezifizität
III. Seizure prediction statistics: ROC
Sen
siti
vit
y1 - Specificity
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-4 -2 0 2 40
0.01
0.02
0.03
0.04
0 0.5 10
0.5
1
Sen
sitiv
ität
1-Spezifizität
III. Seizure prediction statistics: ROC
Sen
siti
vit
y1 - Specificity
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-4 -2 0 2 40
0.01
0.02
0.03
0.04
0 0.5 10
0.5
1
Sen
sitiv
ität
1-Spezifizität
III. Seizure prediction statistics: ROC
Sen
siti
vit
y1 - Specificity
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-4 -2 0 2 40
0.01
0.02
0.03
0.04
0 0.5 10
0.5
1
Sen
sitiv
ität
1-Spezifizität
III. Seizure prediction statistics: ROC
Sen
siti
vit
y1 - Specificity
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-4 -2 0 2 40
0.01
0.02
0.03
0.04
0 0.5 10
0.5
1
Sen
sitiv
ität
1-Spezifizität
III. Seizure prediction statistics: ROC
Sen
siti
vit
y1 - Specificity
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-4 -2 0 2 40
0.01
0.02
0.03
0.04
0 0.5 10
0.5
1
Sen
sitiv
ität
1-Spezifizität
III. Seizure prediction statistics: ROC
Sen
siti
vit
y1 - Specificity
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-4 -2 0 2 40
0.01
0.02
0.03
0.04
0 0.5 10
0.5
1
Sen
sitiv
ität
1-Spezifizität
III. Seizure prediction statistics: ROC
Sen
siti
vit
y1 - Specificity
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-4 -2 0 2 40
0.01
0.02
0.03
0.04
0 0.5 10
0.5
1
Sen
sitiv
ität
1-Spezifizität
III. Seizure prediction statistics: ROC
Sen
siti
vit
y1 - Specificity
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-4 -2 0 2 40
0.01
0.02
0.03
0.04
0 0.5 10
0.5
1
Sen
sitiv
ität
1-Spezifizität
III. Seizure prediction statistics: ROC
Sen
siti
vit
y1 - Specificity
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-4 -2 0 2 40
0.01
0.02
0.03
0.04
0 0.5 10
0.5
1
ROC-Fläche: 0.86
Sen
sitiv
ität
1-Spezifizität
III. Seizure prediction statistics: ROC
Sen
siti
vit
y1 - Specificity
ROC-Area
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a)
0
0.5
1
ROC-Fläche: 0Se
nsi
tivitä
t
b)
0
0.5
1
ROC-Fläche: 1Se
nsi
tivitä
t
c)
0
0.5
1
ROC-Fläche: -1Se
nsi
tivitä
t
d)
0 0.5 10
0.5
1
ROC-Fläche: -0.003Se
nsi
tivitä
t
1-Spezifizität
III. Seizure prediction statistics: ROC
ROC-Area
ROC-Area
ROC-Area
ROC-Area
1 - Specificity
Sensi
tivit
ySensi
tivit
ySensi
tivit
ySensi
tivit
y
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1 2 3 4 50
0.2
0.4
0.6
0.8
1
Zeit [Tage]
cvHTime Profile : BON , TR08-TR09
0.5 0.6 0.7 0.8 0.90
1
2
3
4
cvH
%
InterPrä
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
Se
nsi
tivitä
t
1 - Spezifizität
ROC-Fläche: 0.67
III. Seizure prediction statistics: Example
Sensi
tivit
y1 - Specificity
ROC-Area
Time [days]
e
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For each channel combination 2 * 4 * 2 = 16 combinations
III. Seizure prediction statistics- Parameter of analysis -
• Smoothing of measure profiles (s = 0; 5 min)
• Length of the preictal interval (d = 5; 30; 120; 240 min)
• ROC hypothesis H
- Preictal drop (ROC-Area > 0, )
- Preictal peak (ROC-Area < 0, )
Optimization criterion for each measure: Best mean over patients
Mormann, Kreuz, Rieke et al., Clin Neurophysiol 2005
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I. Continuous EEG – multichannel recordings
II. Calculation of a characterizing measure
III. Investigation of suitability for prediction by means of a seizure prediction statistics
- Sensitivity Performance
- Specificity
IV. Estimation of statistical significance
Predictability of epileptic seizures- Procedure -
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IV. Statistical Validation- Problem: Over-optimization -
Given performance: Significant or statistical fluctuation?
Good measure: „Correspondence“ seizure times - measure profile
To test against null hypothesis:Correspondence has to be destroyed
I. Seizure times surrogatesII. Measure profile surrogates
Randomizationof measure profiles
Randomizationof seizure times
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IV. Statistical Validation- Seizure times surrogates -
Random permutation of the time intervals between actual seizures: Seizure times surrogates
Calculation of the seizure prediction statistics for the original as well as for 19 surrogate seizure times ( p=0.05)
Andrzejak, Mormann, Kreuz et al., Phys Rev E, 2003
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1 2 3 4 5
TL01-TL02
TL02-TL03
TL03-TL04
TL04-TL05
TL05-TL06
TL06-TL07
TL07-TL08
TL08-TL09
TL09-TL10
TR01-TR02
TR02-TR03
TR03-TR04
TR04-TR05
TR05-TR06
TR06-TR07
TR07-TR08
TR08-TR09
TR09-TR10
Zeit [Tage]
Ka
na
lko
mb
ina
tion
- Results: Measure profiles of phase synchronization -
Time [days]
Channel co
mbin
ati
on
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Discrimination of amplitude distributions Interictal Preictal
1. Global effect:
All Interictal All Preictal (1)
2. Local effect:
Interictal per channel comb Preictcal per channel comb (#comb)
Results- Evaluation schemes -
Mormann, Kreuz, Rieke et al., Clin Neurophysiol 2005
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1 2 3 4 5
TL01-TL02
TL02-TL03
TL03-TL04
TL04-TL05
TL05-TL06
TL06-TL07
TL07-TL08
TL08-TL09
TL09-TL10
TR01-TR02
TR02-TR03
TR03-TR04
TR04-TR05
TR05-TR06
TR06-TR07
TR07-TR08
TR08-TR09
TR09-TR10
Zeit [Tage]
Ka
na
lko
mb
ina
tion
- First evaluation scheme -
Time [days]
Channel co
mbin
ati
on
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0
0.2
0.4
0.6
0.8
1
Cmax
I seH
cpH
cvH
seW
cpW
cvW S
sH
sQ S
aH
aq
Maße
| RO
C-F
läch
e |
n.s.p = n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s.
Results: First evaluation scheme |
RO
C-A
rea |
Measures
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Discrimination of amplitude distributions Interictal Preictal
1. Global effect:
All Interictal All Preictal (1)
2. Local effect:
Interictal per channel comb Preictcal per channel comb (#comb)
Results- Evaluation schemes -
Mormann, Kreuz, Rieke et al., Clin Neurophysiol 2005
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1 2 3 4 5
TL01-TL02
TL02-TL03
TL03-TL04
TL04-TL05
TL05-TL06
TL06-TL07
TL07-TL08
TL08-TL09
TL09-TL10
TR01-TR02
TR02-TR03
TR03-TR04
TR04-TR05
TR05-TR06
TR06-TR07
TR07-TR08
TR08-TR09
TR09-TR10
Zeit [Tage]
Ka
na
lko
mb
ina
tion
- Second evaluation scheme -
Time [days]
Channel co
mbin
ati
on
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1 2 3 4 5
TL01-TL02
TL02-TL03
TL03-TL04
TL04-TL05
TL05-TL06
TL06-TL07
TL07-TL08
TL08-TL09
TL09-TL10
TR01-TR02
TR02-TR03
TR03-TR04
TR04-TR05
TR05-TR06
TR06-TR07
TR07-TR08
TR08-TR09
TR09-TR10
Zeit [Tage]
Ka
na
lko
mb
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tion
- Second evaluation scheme -
Time [days]
Channel co
mbin
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on
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1 2 3 4 5
TL01-TL02
TL02-TL03
TL03-TL04
TL04-TL05
TL05-TL06
TL06-TL07
TL07-TL08
TL08-TL09
TL09-TL10
TR01-TR02
TR02-TR03
TR03-TR04
TR04-TR05
TR05-TR06
TR06-TR07
TR07-TR08
TR08-TR09
TR09-TR10
Zeit [Tage]
Ka
na
lko
mb
ina
tion
- Second evaluation scheme -
Time [days]
Channel co
mbin
ati
on
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0 10
0.01
0.02
0.03 TL01-TL02
0 10
0.02
0.04
0.06
0.08TL02-TL03
0 10
0.01
0.02
0.03 TL03-TL04
0 10
0.02
0.04 TL04-TL05
0 10
0.02
0.04
0.06 TL05-TL06
0 10
0.02
0.04
TL06-TL07
0 10
0.02
0.04
0.06
0.08 TL07-TL08
0 10
0.02
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TL08-TL09
0 10
0.02
0.04
0.06 TL09-TL10
0 10
0.01
0.02
0.03 TR01-TR02
0 10
0.02
0.04
TR02-TR03
0 10
0.05
0.1
TR03-TR04
0 10
0.05
0.1
TR04-TR05
0 10
0.02
0.04
TR05-TR06
0 10
0.02
0.04
0.06
0.08 TR06-TR07
0 10
0.02
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0 10
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0.04
TR08-TR09
0 10
0.02
0.04
0.06
0.08TR09-TR10
1 1.5 2-1
0
1
InterPrä
Results: Preictal and interictal distributions
e
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0
0.2
0.4
0.6
0.8
1
| RO
C-F
läch
e |
Cmax
I seH
cpH
cvH
seW
cpW
cvW S
sH
sQ S
aH
aq
Maße
.05p = .05 .05 .05 .05 .05 .05 .05 n.s. n.s. n.s. .05 n.s. .05
Results: Second evaluation scheme|
RO
C-A
rea |
Measures
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Predictability of epileptic seizures - Summary I: Comparison of measures -
General tendency regarding predictive performance:
- Phase synchronization based on Hilbert Transform
- Mutual Information, cross correlation
- …
- Nonlinear interdependencies
Measures of directionality among measures of synchronization
No global effect, but significant local effects
![Page 55: Introduction and motivation Comparitive investigation: Predictive performance of measures of synchronization Statistical validation of seizure predictions:](https://reader038.vdocuments.mx/reader038/viewer/2022110205/56649ca15503460f94960566/html5/thumbnails/55.jpg)
Introduction and motivation
Comparitive investigation:
Predictive performance of measures of synchronization
Statistical validation of seizure predictions:
The method of measure profile surrogates
Summary and outlook
Predictability of epileptic seizures- Content -
* Kreuz, Andrzejak, Mormann et al., Phys. Rev. E (2004)
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Mostly not sufficient data for „Out of sample“ – study (Separation in training- and test sample)
„In sample“ – Optimization (Selection)(Best parameter, best measure, best channel, best patient, …)
Statistical fluctuations difficult to estimate
Seizure prediction- Problem : Statistical validation -
![Page 57: Introduction and motivation Comparitive investigation: Predictive performance of measures of synchronization Statistical validation of seizure predictions:](https://reader038.vdocuments.mx/reader038/viewer/2022110205/56649ca15503460f94960566/html5/thumbnails/57.jpg)
I. Continuous EEG multi channel recordings
II. Calculation of characterizing measures
III. Investigation of suitability for prediction by means of a seizure prediction statistics
IV. Estimation of statistical significance
Predictability of epileptic seizures- Procedure -
- Patient A (18 channel combinations)
- Phase synchronization und event synchronization Q
- ROC, same optimization, for every channel combination
- Method of measure profile surrogates
Hcv
![Page 58: Introduction and motivation Comparitive investigation: Predictive performance of measures of synchronization Statistical validation of seizure predictions:](https://reader038.vdocuments.mx/reader038/viewer/2022110205/56649ca15503460f94960566/html5/thumbnails/58.jpg)
IV. Statistical Validation- Problem: Over-optimization -
Given performance: Significant or statistical fluctuation?
Good measure: „Correspondence“ seizure times - measure profile
To test against null hypothesis:Correspondence has to be destroyed
I. Seizure times surrogatesII. Measure profile surrogates
Randomizationof measure profiles
Randomizationof seizure times
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0
0.5
1Ori)
0
0.5
1S1)
0
0.5
1S2)
0
0.5
1S3)
1 2 3 4 50
0.5
1
Zeit [Tage]
S4)
Measure profile surrogates
Zeit [Tage]
Time [days]
Time [days]
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• Formulation of constraints in cost function E
• Minimization among all permutations of the original measure profile
• Iterative scheme: Exchange of randomly chosen pairs
Measure profile surrogates- Simulated Annealing I -
Schreiber, Phys. Rev. Lett., 1998
• Cooling scheme (Temp. T→0), abort at desired precision
Probability of acceptance:
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104
105
106
107
10-6
10-5
Tem
pera
tur
104
105
106
107
10-5
10-4
10-3
10-2
Iterationsschritte
Kos
tenf
unkt
ion
Measure profile surrogates- Simulated Annealing II -
18 channel combinations(Phase synchronization)
Cost
funct
ion
Tem
pera
ture
Iteration steps
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Measure profile surrogates- Simulated Annealing III -
Properties to maintain:
Recording gaps are not permuted
Ictal and postictal intervals are not permuted
Amplitude distribution Permutation
Autocorrelation Cost function
1
0
0 1
)(
N
nnn xx
NC
max
1
)]()([
OriSurr CCE
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1 2 3 4-1
-0.5
0
0.5
1
Zeit [Tage]
C ( )
Measure profile surrogates- Original autocorrelation functions (Phase sync.) -
Time [days]
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1 2 3 4-1
-0.5
0
0.5
1
Zeit [Tage]
C (
)Measure profile surrogates
- Original autocorrelation functions (Phase sync.) -
Time [days]
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0
0.5
1Ori)
0
0.5
1S1)
0
0.5
1S2)
0
0.5
1S3)
1 2 3 4 50
0.5
1
Zeit [Tage]
S4)
Measure profile surrogates
Time [days]
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0
0.5
1Ori)
0
0.5
1S1)
0
0.5
1S2)
0
0.5
1S3)
1 2 3 4 50
0.5
1
Zeit [Tage]
S4)
Measure profile surrogates
Time [days]
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Measure profile surrogates- Two evaluation schemes -
• Each channel combination separately
• Selection of best channel combination
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0
1 TL01-TL02
0
1 TL02-TL03
0
1 TL03-TL04
0
1 TL04-TL05
0
1 TL05-TL06
0
1 TL06-TL07
0
1 TL07-TL08
0
1 TL08-TL09
0
1 TL09-TL10
0
1 TR01-TR02
0
1 TR02-TR03
0
1 TR03-TR04
0
1 TR04-TR05
0
1 TR05-TR06
0
1 TR06-TR07
0
1 TR07-TR08
0
1 TR08-TR09
0
1 TR09-TR10
Results: Phase synchronization
|ROC|
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0
1 TL01-TL02
0
1 TL02-TL03
0
1 TL03-TL04
0
1 TL04-TL05
0
1 TL05-TL06
0
1 TL06-TL07
0
1 TL07-TL08
0
1 TL08-TL09
0
1 TL09-TL10
0
1 TR01-TR02
0
1 TR02-TR03
0
1 TR03-TR04
0
1 TR04-TR05
0
1 TR05-TR06
0
1 TR06-TR07
0
1 TR07-TR08
0
1 TR08-TR09
0
1 TR09-TR10
Results: Event synchronization
|ROC|
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0
1 TL01-TL02
0
1 TL02-TL03
0
1 TL03-TL04
0
1 TL04-TL05
0
1 TL05-TL06
0
1 TL06-TL07
0
1 TL07-TL08
0
1 TL08-TL09
0
1 TL09-TL10
0
1 TR01-TR02
0
1 TR02-TR03
0
1 TR03-TR04
0
1 TR04-TR05
0
1 TR05-TR06
0
1 TR06-TR07
0
1 TR07-TR08
0
1 TR08-TR09
0
1 TR09-TR10
Results: Phase synchronization
|ROC|
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0
1 TL01-TL02
0
1 TL02-TL03
0
1 TL03-TL04
0
1 TL04-TL05
0
1 TL05-TL06
0
1 TL06-TL07
0
1 TL07-TL08
0
1 TL08-TL09
0
1 TL09-TL10
0
1 TR01-TR02
0
1 TR02-TR03
0
1 TR03-TR04
0
1 TR04-TR05
0
1 TR05-TR06
0
1 TR06-TR07
0
1 TR07-TR08
0
1 TR08-TR09
0
1 TR09-TR10
Results: Event synchronization
|ROC|
![Page 72: Introduction and motivation Comparitive investigation: Predictive performance of measures of synchronization Statistical validation of seizure predictions:](https://reader038.vdocuments.mx/reader038/viewer/2022110205/56649ca15503460f94960566/html5/thumbnails/72.jpg)
Results- Each channel combination separately -
Phase synchronization:
Event synchronization:
Nominal size: p = 0.05 (One-sided test with 19 surrogates)
Independent tests: q = 18 (18 channel combinations)
At least r rejections:
Significant,Null hypothesis rejected !
kqkq
rk
ppk
qP
)1(
0000011.0)8( rP
0015.0)5( rP
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-1
0
1 Phasensynchronisationa)
RO
C-A
rea
-1
0
1 Event Synchronisationb)
RO
C-A
rea
Results- ES II: Selection of best channel combination -
Event synchronization
Phase synchronization
![Page 74: Introduction and motivation Comparitive investigation: Predictive performance of measures of synchronization Statistical validation of seizure predictions:](https://reader038.vdocuments.mx/reader038/viewer/2022110205/56649ca15503460f94960566/html5/thumbnails/74.jpg)
Measure profile surrogates- Two Evaluation schemes -
• Each channel combination separately
Null hypothesis H0 I :
Measure not suitable to find significant number of local effectspredictive of epileptic seizures.
Null hypothesis H0 II :
Measure not suitable to find maximum local effectspredictive of epileptic seizures.
• Selection of best channel combination
![Page 75: Introduction and motivation Comparitive investigation: Predictive performance of measures of synchronization Statistical validation of seizure predictions:](https://reader038.vdocuments.mx/reader038/viewer/2022110205/56649ca15503460f94960566/html5/thumbnails/75.jpg)
Measure profile surrogates- Two Evaluation schemes -
• Each channel combination separately
Null hypothesis H0 I :
Measure not suitable to find significant number of local effectspredictive of epileptic seizures.
Null hypothesis H0 II :
Measure not suitable to find maximum local effectspredictive of epileptic seizures.
• Selection of best channel combination
![Page 76: Introduction and motivation Comparitive investigation: Predictive performance of measures of synchronization Statistical validation of seizure predictions:](https://reader038.vdocuments.mx/reader038/viewer/2022110205/56649ca15503460f94960566/html5/thumbnails/76.jpg)
-1
0
1 Phasensynchronisationa)
RO
C-A
rea
-1
0
1 Event Synchronisationb)
RO
C-A
rea
Results- ES II: Selection of best channel combination -
Event synchronization
Phase synchronization
![Page 77: Introduction and motivation Comparitive investigation: Predictive performance of measures of synchronization Statistical validation of seizure predictions:](https://reader038.vdocuments.mx/reader038/viewer/2022110205/56649ca15503460f94960566/html5/thumbnails/77.jpg)
0
1 Phasensynchronisation
RO
C-F
läch
e
0
1 Event Synchronisation
RO
C-F
läch
eResults
- Selection of best channel combination -
Significant!Null hypothesis H0
II rejected
Not significant!Null hypothesis H0
II accepted
Event synchronization
Phase synchronization
| R
OC
-Are
a |
| R
OC
-Are
a |
![Page 78: Introduction and motivation Comparitive investigation: Predictive performance of measures of synchronization Statistical validation of seizure predictions:](https://reader038.vdocuments.mx/reader038/viewer/2022110205/56649ca15503460f94960566/html5/thumbnails/78.jpg)
Measure profile surrogates- Summary II: Measure profiles surrogates -
Method for statistical validation of seizure predictions
Test against null hypothesis Level of significance
Estimating the effect of „In sample“ – optimization
Phase synchronization more significant than event synchronization.
Given example:
Discrimination of pre- and interictal intervals:
![Page 79: Introduction and motivation Comparitive investigation: Predictive performance of measures of synchronization Statistical validation of seizure predictions:](https://reader038.vdocuments.mx/reader038/viewer/2022110205/56649ca15503460f94960566/html5/thumbnails/79.jpg)
Introduction and motivation
Comparitive investigation:
Predictive performance of measures of synchronization
Statistical validation of seizure predictions:
The method of measure profile surrogates
Summary and outlook
Predictability of epileptic seizures- Content -
![Page 80: Introduction and motivation Comparitive investigation: Predictive performance of measures of synchronization Statistical validation of seizure predictions:](https://reader038.vdocuments.mx/reader038/viewer/2022110205/56649ca15503460f94960566/html5/thumbnails/80.jpg)
Predictability of epileptic seizures- Summary and outlook -
Retrospective investigation: Evidence of significant changes before seizures
Measures good enough for prospective application ???