As previous studies of normal subjects and different age groups have shown, the perception of intonational phrase boundaries (IPHs) induces a positive shift (CPS) in the ERP. The question about the nature of the CPS is still a matter of debate. IPh boundaries are characterized by a set of prosodic cues, e.g. preboundary lenthening, pause, boundary tone. Perceptual studies have shown, that the CPS is also measurable in filtered and hummed speech, where the fundamental frequency plays a crucial role. Nevertheless, if sentence material was presented with a flattened pitch contour, the CPS occurred at each IPh boundary. Hearers are able to aware an IPh boundary without perceiving the full set of prosodic cues in the speech signal.
Moreover, to evaluate the perception of the IPh boundaries in dependence of brain functions, sentences were presented to unilateral left and right lesioned patients. Both groups showed differences in processing of IPh boundaries in comparison to healty controls. The RH group clearly displays the processing in an extended time window, whereas the LH group might have problems to integrate linguistic based prosodic features into speech within an appropriate time. The results of the studies lead to an interpretation of the CPS as a component which reflects the segmentation of the speech input.