Shifting concepts of autoregulation: Commentary to 'static autoregulation in humans'.

Advances in imaging techniques have transformed our understanding of cerebral autoregulation. Older imaging techniques provided measurements of cerebral blood flow (CBF) that reflected the average CBF over a window of 10-20 minutes. A key finding, dating back to 1959, was that CBF remained more or less stable over a remarkably wide range of changes in blood pressure. Modern techniques can measure changes in CBF within the time frame of a heartbeat. They have revealed, paradoxically, a remarkable instability of CBF. This commentary attempts to reconcile these seemingly contradictory observations.