Coupling of total hemoglobin concentration, oxygenation, and neural activity in rat somatosensory cortex

Neuron. 2003 Jul 17;39(2):353-9. doi: 10.1016/s0896-6273(03)00403-3.


Recent advances in brain imaging techniques, including functional magnetic resonance imaging (fMRI), offer great promise for noninvasive mapping of brain function. However, the indirect nature of the imaging signals to the underlying neural activity limits the interpretation of the resulting maps. The present report represents the first systematic study with sufficient statistical power to quantitatively characterize the relationship between changes in blood oxygen content and the neural spiking and synaptic activity. Using two-dimensional optical measurements of hemodynamic signals, simultaneous recordings of neural activity, and an event-related stimulus paradigm, we demonstrate that (1) there is a strongly nonlinear relationship between electrophysiological measures of neuronal activity and the hemodynamic response, (2) the hemodynamic response continues to grow beyond the saturation of electrical activity, and (3) the initial increase in deoxyhemoglobin that precedes an increase in blood volume is counterbalanced by an equal initial decrease in oxyhemoglobin.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Brain Mapping
  • Computer Simulation
  • Demography
  • Electric Stimulation
  • Electrophysiology / methods
  • Evoked Potentials, Somatosensory / physiology
  • Hemodynamics / physiology
  • Hemoglobins / metabolism*
  • Magnetic Resonance Imaging / methods
  • Neurons / physiology*
  • Nonlinear Dynamics
  • Oxygen / metabolism*
  • Rats
  • Somatosensory Cortex / blood supply
  • Somatosensory Cortex / cytology
  • Somatosensory Cortex / metabolism*
  • Spectrum Analysis / methods
  • Time Factors


  • Hemoglobins
  • deoxyhemoglobin
  • Oxygen