The effect of the skull on event-related P300.
OBJECTIVE
Event-related potentials (EP) indicate neuronal processes with a high temporal resolution, while functional magnetic resonance imaging (fMRI) has a high spatial distribution. Information from both techniques may complement each other. However, this combination is fraught with difficulty because of a possible interference of the skull or the scalp with scalp-recorded EP. The aim of the present study was to investigate this influence of skull and scalp thicknesses on event-related P300 potentials.


METHODS
Thirty healthy controls were examined using an auditory evoked P300 elicited by a standard oddball paradigm. Skull and scalp thicknesses were determined using coronal T2-weighted magnetic resonance imaging (MRI).


RESULTS
P3b-amplitudes were significantly correlated with temporo-parietal skull thickness (r=-0.42; P=0.021; regression slope of -1.14 microV/mm skull thickness), whereas scalp had no influence on P300. The amplitude of the more frontal subcomponent P3a was not related to frontal skull thickness.


CONCLUSIONS
Therefore, the utility of P300 as a research tool can be enhanced when adjustment for skull thickness is made.
Frodl
T
T
Laboratory for Neuroimaging of Functional Psychosis, Department of Psychiatry, Ludwig-Maximilians-University Munich, Nussbaumstrasse 7, 80336 Munich, Germany. thomas.frodl-bauch@psy.med.uni-muenchen.de
Meisenzahl
E M
EM
Müller
D
D
Leinsinger
G
G
Juckel
G
G
Hahn
K
K
Möller
H J
HJ
Hegerl
U
U
D000328:Adult; D018913:Event-Related Potentials, P300; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012535:Scalp / Q000502:physiology; D012886:Skull / Q000502:physiology*