APPLICATION OF DIMENSION ESTIMATION AND SURROGATE DATA TO THE TIME EVOLUTION OF EEG TOPOGRAPHIC VARIABLES

Dimensional complexity (estimated correlation dimension) was measured for two topographic EEG time series: (a) the time evolution of global field power (GFP) and (b) the time evolution of sequential dissimilari ty (SQD) for resting, eyes-closed and eyes-open data. Eyes-closed GFP and eyes-closed/open SQD all had an element of nonlinearity in their d ynamics as evidenced by increased dimensional complexity associated wi th the phase-angle randomization, Gaussian surrogate-data procedure. H owever, none of the three gave any evidence of being deterministic cha otic processes. Eyes-open GFP dimensional complexity could not be dist inguished from a linear-stochastic process.