CEREBRAL VASOMOTION - A 0.1-HZ OSCILLATION IN REFLECTED LIGHT IMAGINGOF NEURAL ACTIVITY

Imaging of scattered and reflected light from the surface of neural st ructures can reveal the functional architecture within large populatio ns of neurons. These techniques exploit, as one of the principal signa l sources, reflectance changes produced by local variation in blood vo lume and oxygen saturation related to neural activity. We found that a major source of variability in the captured light signal is a pervasi ve low-frequency (0.1-Hz) oscillation which apparently results from re gional cerebral blood flow. This signal is present in brain parenchyma as well as the microvasculature and exhibits many characteristics of the low-frequency ''vasomotion'' signals observed in peripheral microc irculation. Concurrent measurements in brain with a laser Doppler how meter contained an almost identical low-frequency signal. The presence of the 0.1-Hz oscillation in the cerebral microcirculation could unde rlie a portion of the previously described characteristics reported in reflected-light imaging studies. The prevalence of the oscillatory ph enomena in the brain raises substantial temporal sampling issues for o ptical imaging and for other visualization techniques which depend on changes in regional cerebral blood dynamics, such as functional magnet ic resonance imaging. (C) 1996 Academic Press, Inc.