The spatial location of EEG electrodes: locating the best-fitting sphere relative to cortical anatomy.
The location of the international 10-20 system electrode positions and 14 fiducial landmarks are described in cartesian coordinates (+/- 1.4 mm average accuracy). Six replications were obtained on 3 separate days from 4 normal subjects, who were compared to each other with a best-fit sphere algorithm. Test-retest reliability depended on the electrode position: the parasagittal electrodes were associated with greater measurement errors (maximum 7 mm) than midline locations. Location variability due to head shape was greatest in the temporal region, averaging 5 mm from the mean. For each subject's electrode locations a best-fitting sphere was determined (79-87 mm radius, 6% average error). A surface-fitting algorithm was used to transfer the electrode locations and best-fitting sphere to MR images of the brain and scalp. The center of the best-fitting sphere coincided with the floor of the third ventricle 5 mm anterior to the posterior commissure. The melding of EEG electrode location information with brain anatomy provides an empirical basis for associating hypothetical equivalent dipole locations with their anatomical substrates.
Towle
V L
VL
Department of Neurology, University of Chicago, IL 60637.
Bolaños
J
J
Suarez
D
D
Tan
K
K
Grzeszczuk
R
R
Levin
D N
DN
Cakmur
R
R
Frank
S A
SA
Spire
J P
JP
D000328:Adult; D001921:Brain / Q000033:anatomy & histology* / Q000502:physiology; D001931:Brain Mapping; D004566:Electrodes; D004569:Electroencephalography / Q000295:instrumentation*; D005074:Evoked Potentials, Visual / Q000502:physiology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D010775:Photic Stimulation