Changes in cerebral arterial, tissue and venous oxygenation with evoked neural stimulation: implications for hemoglobin-based functional neuroimaging.

Little is known regarding the changes in blood oxygen tension (P(O2)) with changes in brain function. This work aimed to measure the blood P(O2) in surface arteries and veins as well as tissue with evoked somato-sensory stimulation in the anesthetized rat. Electrical stimulation of the forepaw induced average increases in blood flow of 44% as well as increases in the tissue P(O2) of 28%.

Source of nonlinearity in echo-time-dependent BOLD fMRI.

Stimulation-induced changes in transverse relaxation rates can provide important insight into underlying physiological changes in blood oxygenation level-dependent (BOLD) contrast. It is often assumed that BOLD fractional signal change (DeltaS/S) is linearly dependent on echo time (TE). This relationship was evaluated at 9.