fMRI and EEG responses to periodic visual stimulation

Citation
Cn. Guy et al., fMRI and EEG responses to periodic visual stimulation, NEUROIMAGE, 10(2), 1999, pp. 125-148
Citations number
29
Categorie Soggetti
Neurosciences & Behavoir
Journal title
NEUROIMAGE
ISSN journal
10538119 → ACNP
Volume
10
Issue
2
Year of publication
1999
Pages
125 - 148
Database
ISI
SICI code
1053-8119(199908)10:2<125:FAERTP>2.0.ZU;2-Y
Abstract
EEG/VEP and fMRI responses to periodic visual stimulation are reported. The purpose of these experiments was to look for similar patterns in the time series produced by each method to help understand the relationship between the two. The stimulation protocol was the same for both sets of experiments and consisted of five complete cycles of checkerboard pattern reversal at 1.87 Hz for 30 s followed by 30 s of a stationary checkerboard. The fMRI da ta was analyzed using standard methods, while the EEG was analyzed with a n ew measurement of activation-the VEPEG. Both VEPEG and fMRI time series con tain the fundamental frequency of the stimulus and quasi harmonic component s-an unexplained double frequency commonly found in fMRI data. These result s have prompted a reappraisal of the methods for analyzing fMRI data and ha ve suggested a connection between our findings and much older published inv asive electrophysiological measurements of blood flow and the partial press ures of oxygen and carbon dioxide. Overall our new analysis suggests that f MRI signals are strongly dependant on hydraulic blood flow effects. We dist inguish three categories of fMRI signal corresponding to: focal activated r egions of brain tissue; diffuse nonspecific regions of steal; and major cer ebral vessels of arterial supply or venous drainage. Each category of signa l has its own finger print in frequency, amplitude, and phase. Finally, we put forward the hypothesis that modulations in blood flow are not only the consequence but are also the cause of modulations in functional activity, ( C) 1999 Academic Press.