Cerebral haemoglobin oxygenation during sustained visual stimulation--a near-infrared spectroscopy study.
Using near-infrared spectroscopy, we investigated the time-course of the concentrations of oxygenated haemoglobin, [oxy-Hb], and deoxygenated haemoglobin [deoxy-Hb], in the occipital cortex of healthy human adults during standard sustained visual stimulation. Within a few seconds after stimulation (by coloured dodecahedron), we observed a decrease in [deoxy-Hb], peaking after 13 s ('initial undershoot'). In the subsequent 1-2 min, in seven out of ten subjects, [deoxy-Hb] gradually returned to a plateau closer to the baseline level. After cessation of stimulation, there was a 'post-stimulus overshoot' in [deoxy-Hb]. There was a statistically significant correlation between the size of the 'initial undershoot' and the post-stimulus overshoot'. The concentration of oxyhaemoglobin increased upon functional activation. However, in the mean across all subjects there was no 'initial overshoot'. After approximately 19 s it reached a plateau and remained constantly elevated throughout the activation period. After cessation of activation there was a 'post-stimulus undershoot' of oxyhaemoglobin. It is important to consider the time-course of haemoglobin oxygenation when interpreting functional activation data, especially those data obtained with oxygenation-sensitive methods, such as BOLD-contrast fMRI.
Heekeren
H R
HR
Department of Neurology, Charité, Humboldt-University Berlin, Germany.
Obrig
H
H
Wenzel
R
R
Eberle
K
K
Ruben
J
J
Villringer
K
K
Kurth
R
R
Villringer
A
A
D000328:Adult; D003118:Color Perception; D005260:Female; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008297:Male; D009778:Occipital Lobe / Q000098:blood supply* / Q000378:metabolism*; D010108:Oxyhemoglobins / Q000378:metabolism*; D010775:Photic Stimulation; D012044:Regression Analysis; D013055:Spectrophotometry, Infrared / Q000379:methods
D006454:Hemoglobins; D010108:Oxyhemoglobins