C. Janz et al., TIME-RESOLVED MEASUREMENTS OF BRAIN ACTIVATION AFTER A SHORT VISUAL STIMULUS - NEW RESULTS ON THE PHYSIOLOGICAL-MECHANISMS OF THE CORTICAL RESPONSE, NMR in biomedicine, 10(4-5), 1997, pp. 222-229
This paper presents examinations of the time course of the signal from
the visual cartes following a brief (2 s) light stimulus, Signal was
generated from a 2x2x2 ml voxel using a modified point-resolved spectr
oscopy experiment. In accordance with previous studies a triphasic tim
e course was observed. The results indicate that the observable signal
contains contributions from wan blood oxygen level dependent signal c
hanges occurring immediately after the onset of stimulation, The respo
nse to multiple stimuli could be fitted with a response model which is
linear with respect to the BOLD-phase of the response, This suggests
that the experiments using a very weak stimulus were performed below t
he limit of the arterial reserve, This is in marked contrast to other
studies performed by functional magnetic resonance imaging as well as
optical imaging, First results using echo planar imaging confirm the c
ommon origin of the signals in the activated cortical areas. (C) 1997
John Wiley & Sons, Ltd.