Intraindividual Specificity and Stability of Human
EEG: Comparing a Linear vs a Nonlinear Approach.

R.M. Dünki, G.B. Schmid & H.H. Stassen, Methods of Information in Medicine 39: 78 - 82, (2000)

We have applied the so-called ``unfolding dimension'' approach to reanalyze an earlier longitudinal EEG study. Both linear and nonlinear approaches show that the EEG comprises a static, person-specific part upon which nonstatic and state-specific parts are superimposed. The intraindividual specificity and stability of the genetic part are similar between methods. This is assessed by comparing the outcome of a person to his own outcomes at later times (14 days and 5 years later). The nonlinear method revealed a median correlation coefficient r = 0.55, whereas advanced linear methods showed a median r = 0.84. An apparent effect for the 5-year interval was detected with the nonlinear method and is discussed in terms of the different assumptions of the two approaches concerning EEG signal generation.