Suppressed neuronal activity and concurrent arteriolar vasoconstriction may explain negative blood oxygenation level-dependent signal

J Neurosci. 2007 Apr 18;27(16):4452-9. doi: 10.1523/JNEUROSCI.0134-07.2007.

Abstract

Synaptic transmission initiates a cascade of signal transduction events that couple neuronal activity to local changes in blood flow and oxygenation. Although a number of vasoactive molecules and specific cell types have been implicated, the transformation of stimulus-induced activation of neuronal circuits to hemodynamic changes is still unclear. We use somatosensory stimulation and a suite of in vivo imaging tools to study neurovascular coupling in rat primary somatosensory cortex. Our stimulus evoked a central region of net neuronal depolarization surrounded by net hyperpolarization. Hemodynamic measurements revealed that predominant depolarization corresponded to an increase in oxygenation, whereas predominant hyperpolarization corresponded to a decrease in oxygenation. On the microscopic level of single surface arterioles, the response was composed of a combination of dilatory and constrictive phases. Critically, the relative strength of vasoconstriction covaried with the relative strength of oxygenation decrease and neuronal hyperpolarization. These results suggest that a neuronal inhibition and concurrent arteriolar vasoconstriction correspond to a decrease in blood oxygenation, which would be consistent with a negative blood oxygenation level-dependent functional magnetic resonance imaging signal.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Arterioles / physiology*
  • Blood Volume
  • Brain Mapping
  • Cerebral Cortex / physiology*
  • Hemoglobins / metabolism
  • Neurons / physiology*
  • Oxygen / blood*
  • Oxyhemoglobins / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Synaptic Transmission / physiology*
  • Vasoconstriction / physiology*

Substances

  • Hemoglobins
  • Oxyhemoglobins
  • deoxyhemoglobin
  • Oxygen