Activation flow coupling, increases in neuronal activity leading to changes in cerebral blood flow (CBF), is the basis of many neuroimaging methods. An early rise in deoxygenation, the "initial dip," occurs before changes in CBF and cerebral blood volume (CBV) and may provide a better spatial localizer of early neuronal activity compared with subsequent increases in CBF. Imaging modality, anesthetic, degree of oxygenation, and species can influence the magnitude of this initial dip. The observed initial dip may reflect a depletion of mitochondrial oxygen (O2) buffers caused by increased neuronal activity. Changes in CBF mediated by nitric oxide (NO) or other metabolites and not caused by a lack of O2 or energy depletion most likely lead to an increased delivery of capillary O2 in an attempt to maintain intracellular O2 buffers.

Original languageEnglish
Pages (from-to)1-6
Number of pages6
JournalJournal of Cerebral Blood Flow and Metabolism
Issue number1
StatePublished - Jan 2004


  • Activation flow coupling
  • Cerebral blood flow and metabolism
  • Deoxyhemoglobin
  • Initial dip


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