Nonlinear Time Series Analysis on EEG

Review

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Takens’s delay embedding theorem (1981) scalar time series m -dimensional vectors Time Lag:  Mutual information (A. M. Fraser, Physical Review A 33, 1134) Embedded dimension: m False nearest neighbor method (M. B. Kennel, Physical Review A 45, 3403)

Quantitative value on dynamical complexity P. Grassberger’s Correlation dimension (D 2 ) S. H. O.: D 2 = 1 Lorenz attractor: D 2 = 2.05

Chaotic Dynamics in Brain Activity A. Babloyantz (1985) Differentiated D 2 in SWS stages (a) awake (b) stage2 sleep (c) stage4 sleep (d,e) REM (a) (b) (c) (d)

Strange Attractors in Intracranial Structure J. Roschke and E. Basar Differentiated D 2 in functionally independent brain structures D GEA >D RF >D HI

Experimental protocol Male Sprague Dawley rats (250~350g) The EEG signals were recorded in the somatosenseroy cortex (bragma –1, ML -3) with a 1x16 (16 channels) Michigan probe The sampling rates of recording were 6KHz and 250Hz in a data acquisition system based on PC system (TDT Inc. USA) Each epoch of 8s time series data (among a total of 200s recording period) was used for data analysis The data analysis program was based on the “Nonlinear Time Series Analysis” sub programs (in C language) written by Rainer Hegger et. al. 150um

EEG raw data

Data Process Time delay Embedded dimension Delay Reconstruction Raw data Correlation Dimension (a) (b)

Results The EEG data of 16 channels can be classified into 5 types with different phase portraits and D 2. After anatomical mapping, cortical layer IV (channel 5,6) showed the higher D 2. This may imply more complex neuronal activity on layer IV. D 2 decreased with increasing different Halothane anesthesia concentration.

Principle of Neural Science Stellate neurons are the principle target of thalamocortical axons. The axons of Stellate neurons project and terminate on the apical dendrites of pyramidal cells who somas lie in layers II, III, and V. Schematic cortical circuit