Datensatz

Zusammenfassung

In most experiments using event-related brain poten- tials (ERPs), there is a straightforward way to define—on theoret- ical grounds—which of the conditions tested is the experimental condition and which is the control condition. If, however, theoret- ical assumptions do not give sufficient and unambiguous informa- tion to decide this question, then the interpretation of an ERP effect becomes difficult, especially if one takes into account that certain effects can be both a positivity or a negativity on the basis of the morphology of the pattern as well as with respect to peak latency (regard for example, N400 and P345). Exemplified with an ERP experiment on language processing, we present such a critical case and offer a possible solution on the basis of nonlinear data analysis. We show that a generalized polarity histogram, the word statistics of symbolic dynamics, is in principle able to distinguish negative going ERP components from positive ones when an appropriate encoding strategy, the half wave encoding is employed. We pro- pose statistical criteria which allow to determine ERP components on purely methodological grounds