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 vibrotactile stimulation ultimately must lead to increased oxygen consumption consumption. Twenty-two healthy right-handed young volunteers underwent positron emission tomography (PET) with the [O-15]water bolus injection method to measure water clearance (K-1(H2O) an index of blood flow (CBF), and with the [O-15]oxygen bolus inhalation method to measure CMRO2. The CMRO2 was measured 30 seconds and 20 minutes after onset of intermittent (1 second on, 1 second off) vibrotactile stimulation (110 Hz) and compared with baseline measurements without stimulation, The K-1(H2O) and CMRO2 changes (Delta K-1(H2O) and Delta CMRO2) were determined using intersubject averaging, together with magnetic resonance imaging based stereotaxic registration technique. The K-1(H2O) increase was 21 +/- 4% and 12 +/- 4% at 30 seconds and 20 minutes after onset of stimulation, respectively. No significant increase of CMRO2 was found until 30 minutes after the onset of stimulation. The authors conclude that blood flow and oxidative metabolism undergo uncoupling during sustained phasic stimulation of the sensory hand area. Therefore, neuronal activity stimulated in this manner does not rely on significantly increased oxidative phosphorylation.