McConnell Brain Imaging Center, Montreal Neurological Institute, and Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada

Correspondence: Albert Gjedde, Positron Emission Tomography Center, Aarhus General Hospital, 44 Norrebrogade, Aarhus C, Denmark 8000.

¹Dr. S. Ohta's current address is the Department of Neurological Surgery, Ehime University Hospital, Matsuyama, Ehime Prefecture, Shikoku, Japan.

Received 16 June 1995; Revised 14 July 1998; Accepted 22 July 1998.

Abstract

Vibrotactile stimulation of the hand elicits no increase in oxygen consumption commensurate with the increase in blood flow measured in human sensory cortex. To test the hypothesis that previous failures to detect a proportionate increase in oxygen consumption could be an artefact of the sequential bolus, or three-step, method used to measure this parameter in the human brain in vivo, the authors compared the measurements with the results of a novel single bolus, or one-step, method of measuring oxygen consumption. The time of completion of the three-step method was 40 to 50 minutes, whereas the one-step method lasted only 3 minutes. The baseline whole-brain oxygen consumption averaged 185 32 mol hg^-1 min^-1 by the three-step method and 153 15 mol hg^-1 min^-1 by the one-step method. Vibrotactile stimulation did not elicit a significant increase in oxygen consumption measured by either method. This finding rejects the hypothesis that failure to detect an increase of oxygen consumption could be an artefact caused by limitations of the method used previously. Conversely, it also rejects the hypothesis that observations of an increase of oxygen consumption by the new method are artefacts caused by limitations of the one-step method.