Transient functional blood flow change in the human brain measured noninvasively by diffusing-wave spectroscopy.
Multispeckle diffusing-wave spectroscopy (DWS) is used to measure blood flow transients in the human visual cortex following stimulation by 7.5 Hz full-field and checkerboard flickering. The average decay time tau(d) characterizing the decay of the DWS autocorrelation function shows a biphasic behavior; within about 2 s after stimulation onset, tau(d) increases rapidly to about 6% above the baseline value. At later times, tau(d) slowly decreases and reaches a steady-state value about 5% below the baseline value after about 15 s. The initial increase of the DWS signal suggests a transient reduction of the cortical blood flow velocity shortly after stimulation onset. Measurements of this transient response at different positions over the primary visual cortex show a spatial pattern different from the one measured by electroencephalography.
Li
J
J
Fachbereich Physik, Universitat Konstanz, Konstanz, Germany.
Ninck
M
M
Koban
L
L
Elbert
T
T
Kissler
J
J
Gisler
T
T
D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D013055:Spectrophotometry, Infrared / Q000379:methods*; D014793:Visual Cortex / Q000098:blood supply / Q000502:physiology*