Dipole source analysis of temporal slow waves in the elderly

Background: Temporal low-voltage irregular delta-waves (TLID) are often found in elderly subjects. The physiological significance of TLID has not been clarified; however, our previous studies suggest that TLID are associated with mild cerebrovascular dysfunction. Objective: The present study aimed to reveal the origin of TLID and their neural mechanisms by dipole source modeling. Methods: From electroencephalography records taken from 21 scalp electrodes, clear and typical TLID of 6 elderly subjects ( mean age, 69 8 6.2 years) were selected. Among these, we selected and averaged 7-12 clear TLID on the left side in each subject, and estimated a single equivalent current dipole for the averaged TLID. Results: The best equivalent current dipoles were estimated to be located in the medial part of the temporal lobe in or near the parahippocampal gyrus in the hemisphere ipsilateral to the TLID, with a high reliability in all subjects. Conclusions: Considering the source localization of TLID, TLID seem to indicate certain dysfunctions of the hippocampus 7or adjacent regions. This is the first study to report the cerebral origin of TLID and suggest its physiological Copyright (c) 2008 S. Karger AG, Basel.