간질성 뇌파의 시공간 패턴 분석

김 정 애 , 한 승 기충북대학교 물리학과

임 태 규한국전자통신연구원 , 인체정보연구부

이 상 건 , 남 현 우서울대학교병원 신경과

.

간질 (Epilepsy) ?신경계의 변화에 의한 강한 발화 활동 - 신경세포의 과도한 발화 - 신경계의 변화에 의한 강한 동기화 : 흥분성 영향의 증가 ,

억제성 영향의 감소 - 간질성 발작 거동뇌파의 변화 , 뇌파 분석간질 뇌파의 특징 추출 , 간질 발현 시간 예측 , 간질 위치 추정

Invasive EEG(Epileptic seizure) 간질뇌파 ( 서울대병원 간질센터 )-Lateral Temporal Lobe Epilepsy(L-TLE) -Depth EEG-32 channels, 200sec recording (interictal, ictal, postictal)

-5subject

Time(sec)

channel

Interictal ictal

EEG Electrodes

54321

109876

1514131211

2019181716

21222324252627

28

29

30

Temporal changes, spatial dependence

Correlations between different measures

Robustness of pattern: inter-trials

Linear analysis: power spectrum

-theta(3-7Hz), alpha(8-13Hz), beta(20-30Hz)

Statistical analysis: Jensen-Shannon

divergence

- amplitude, peak time, variance, kurtosis

Nonlinear analysis: mutual information

-correlation time, correlation dimension

Spatio-temporal Pattern

Power spectrum analysis(1):Frequency band: theta(3~7Hz), alpha(8~13Hz),

beta(20~30Hz)

spectrum sum: theta, alpha, beta is localization

power ratio :

-rhythm order : beta->alpha-> theta->total power

Total power 3~7hz 8~13hz 20~30hz

Spectrum sum

Power ratio

Power spectrum analysis: inter-trial variations

Time map of beta spectrum

Time

sgo1

sgo2

sgo3

sgo4

sgo5

Statistical analysis:

0])H[SLl

]H[SLl

(H[S])S,(SJS 22

11

212

pplogH[p],SSS,llL 22121

Change in statistical properties of amplitude distribution

- boundary between two distributions?

분석구간

Jensen-Shannon divergence)()1()( txtxtz

2S1SS

JS-E Kurt STD

Statistical measures at JS-E maximum

Temporal mapping of JS-E

Plot of JS-divergence:

Time of change in amplitude distribution

Position of most dominant changes

Statistical measures

Plot of JS-divergence: inter-trial variations

sgo1

sgo2

sgo3

sgo4

sgo5

Time map of JS-E

Time

Nonlinear analysisNonlinear dynamics underlying the bursting neural activities Nonlinear measures characterizing the temporal behaviors

Mutual information

ji

ij

ji,ij pp

)(p)ln(p)s(

Avera

ge m

utu

al in

form

ati

on

Time(sec)

channel

Corr

ela

tion

tim

e(m

sec)

Temporal mapping of correlation time

Plot of correlation time:

decrease in the correlation time during ital period no specific channel dependence

Variability of the spatial mapping

sgo1

sgo2

sgo3

sgo4

sgo5

Plot of correlation time:inter-trial variations

Temporal maping of correlation time

Time

sgo1 sgo2 sgo3 sgo4 sgo5

JS-E

Beta

Correl.time

Partial overlapping between the temporal maps of JS-E and beta

No similarity with the temporal map of correlation time

Comparison of temporal maps of JS-E , Beta, Correlation time

Correlation between inter-trials and different maps of JS-E, beta spectrum , and correlation time

High inter-trial correlations for JS-E and beta spectrum

Low inter-trial correlation for correlation time

Correlations between different maps are weak

Neural network model of Epileptic seizure generation: CA3 in Hippocampus [Tateno,1998]

synafleakKCaNa IIIIIIdt

dVC

- Pyramidal cell (Δ)

- Inhibitory inter-neuron ()

synleakKNa IIIdt

dVC

))(( VVtCI synsynsyn

- Synaptic current

Iaf : 해마 외부에서 가해지는 tonic input

k

kstimsynfield RIII /)(

- Field current

신경 모형계 (16x16) 의 시공간 발화 패턴

Cpp=0.001

Cpp=0.003

Cpp=0.005

Cpp=0.008

time

STDP (Spike-Timing Dependent Plasticity)

[G-q. Bi and M-m. Poo, 1998]

max)( CtFCC synsyn

0),/exp(

0),/exp()(

ttA

ttAtF

Normal hippocampus : A+ ~ A-Abnormal hippocampus : ?

Δt : tpost - tpre

A+ : maximal synaptic strengthening

A- : maximal synaptic weakening

gaf=0.005uS, CPI=0.02uS, CIP=0.02uS

A+ 와 A- 에 따른 신경모형계의 거동 변화 (2)

결론 및 논의Spatio-temporal pattern analysis• Power spectrum : - spatio-temporal pattern of beta rhythm is more informative

- lateral temporal lobe epilepsy is close to the hippocampus

- beta rhythm is generated in the hippocampus

• JS-entropy : - earlier rise of JS entropy in several channels

- the position of rises are consistent with diagnostic of the medical doctors

- the shape of distribution function, es. kurtosis : seizure generation • Mutual information : correlation time

- short correlation time for ictal rhythm

- non-specific map: no information on the localization

• Neural network model of seizure generation:

- CA3 model + Spike-Timing Dependent Plasticity

- unbalance between synaptic strengthening and weakining