IT has been known for a long time that changes in cerebral metabolic activity, whether localized or generalized, are followed by concomitant changes in the blood flow. In 1890, Roy and Sherrington1 concluded from their experiments that... the chemical products of cerebral metabolism contained in the lymph which bathes the walls of the arterioles of the brain can cause variations of the calibre of the cerebral vessels: in this reaction the brain possesses an intrinsic mechanism by which its vascular supply can be varied locally in correspondence with local variations of functional activity.
Many other studies have supported their conclusions. Increases in total brain metabolism produced pentylenetetrazol (Metrazol) administration2-6 or stimulation of the reticular-activating system in the brain stem (RAS)7-15 were followed by an increased cerebral blood flow (CBF). Activation of specific parts of the brain by afferent stimulation was followed by local vasodilatation and increase
Shalit MN, Reinmuth OM, Shimojyo S, Scheinberg P. Carbon Dioxide and Cerebral Circulatory Control: III. The Effects of Brain Stem Lesions. Arch Neurol. 1967;17(4):342–353. doi:10.1001/archneur.1967.00470280008002
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