Dynamics of regional cerebral blood flow for various visual stimuli.

Isotope tracer methods for measuring regional cerebral blood flow or metabolism do not provide data on the dynamics of the fast adjustment of local cerebral blood flow. Measuring intracranial flow patterns of the posterior cerebral artery by means or 2 MHz pulsed transcranial Doppler ultrasonography demonstrated that detailed dynamic effects of various visual patterns on local cerebral perfusion can be recorded, and that visual stimuli of different complexity as well as the strategy of stimulus perception cause distinct flow velocity changes in the occipital cortex involved in information processing. This type of on--line analysis may become a powerful tool for detecting fast autoregulatory mechanisms in relation to purely functional cerebral changes.