Oxygen consumption of cerebral cortex fails to increase during continued vibrotactile stimulation

The coupling of oxidative metabolism to the blood flow of the sensory motor hand area is uncertain. The authors tested the hypothesis that continued v ibrotactile stimulation ultimately must lead to increased oxygen consumptio n consumption. Twenty-two healthy right-handed young volunteers underwent p ositron emission tomography (PET) with the [O-15]water bolus injection meth od to measure water clearance (K-1(H2O) an index of blood flow (CBF), and w ith the [O-15]oxygen bolus inhalation method to measure CMRO2. The CMRO2 wa s measured 30 seconds and 20 minutes after onset of intermittent (1 second on, 1 second off) vibrotactile stimulation (110 Hz) and compared with basel ine measurements without stimulation, The K-1(H2O) and CMRO2 changes (Delta K-1(H2O) and Delta CMRO2) were determined using intersubject averaging, to gether with magnetic resonance imaging based stereotaxic registration techn ique. The K-1(H2O) increase was 21 +/- 4% and 12 +/- 4% at 30 seconds and 2 0 minutes after onset of stimulation, respectively. No significant increase of CMRO2 was found until 30 minutes after the onset of stimulation. The au thors conclude that blood flow and oxidative metabolism undergo uncoupling during sustained phasic stimulation of the sensory hand area. Therefore, ne uronal activity stimulated in this manner does not rely on significantly in creased oxidative phosphorylation.