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Stimulus dependence of oxygenation-sensitive MRI responses to sustained visual activation

✍ Scribed by G. Krüger; A. Kleinschmidt; J. Frahm

Publisher
John Wiley and Sons
Year
1998
Tongue
English
Weight
117 KB
Volume
11
Category
Article
ISSN
0952-3480

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✦ Synopsis

Oxygenation-sensitive MRI responses to repetitive and sustained visual activation were compared for stimuli with different temporal, spatial, and luminance contrasts, i.e. reversing checkerboard, flashing diffuse red light, and stationary diffuse gray light with darkness as a control. All paradigms elicited an initial oxygenation 'overshoot' as well as a post-stimulus 'undershoot'. However, whereas flashing and stationary diffuse light resulted in more than a 50% decrease of the initial signal response after 6 min of stimulation, checkerboard responses remained largely unaffected (less than 20% signal attenuation). The demonstration of a stimulus dependence for sustained visual activation reconciles apparently contradictory reports for stimuli involving checkerboards as opposed to goggles, flickerlight, and movies. It may be caused by stimulus-dependent adjustments of neuronal activity, oxygen consumption, blood flow, or blood volume.

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