Coupling of total hemoglobin concentration, oxygenation, and neural activity in rat somatosensory cortex.
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.
Devor
Anna
A
Massachusetts General Hospital NMR Center, Harvard Medical School, Charlestown, MA 02129, USA. adevor@nmr.mgh.harvard.edu
Dunn
Andrew K
AK
Andermann
Mark L
ML
Ulbert
Istvan
I
Boas
David A
DA
Dale
Anders M
AM
D000818:Animals; D001931:Brain Mapping; D003198:Computer Simulation; D003710:Demography; D004558:Electric Stimulation; D004594:Electrophysiology / Q000379:methods; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology; D006454:Hemoglobins / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods; D009474:Neurons / Q000502:physiology*; D017711:Nonlinear Dynamics; D010100:Oxygen / Q000378:metabolism*; D051381:Rats; D013003:Somatosensory Cortex / Q000098:blood supply / Q000166:cytology / Q000378:metabolism*; D013057:Spectrum Analysis / Q000379:methods; D013997:Time Factors
D006454:Hemoglobins; C100003:deoxyhemoglobin; D010100:Oxygen