Temporal patterns of uncoupling between oxidative metabolism and regional cerebral blood flow demonstrated by functional magnetic resonance imaging

Author(s): Wu, D., Lewin, J. S., Miller, D., Lerner, A. J., Friedland, R. P.

Journal/Book: Invest Radiol. 1995; 30: 227 East Washington Square, Philadelphia, PA 19106. Lippincott-Raven Publ. 625-633.

Abstract: RATIONALE AND OBJECTIVES Brain activation can be detected by functional magnetic resonance imaging, Termination of stimulation can cause drop of postactivation signal below preactivation baseline; the nature of this ''undershoot'' remains controversial, The authors investigated postactivation signal after stimulation of the visual cortex with photic stimuli of different duration, METHODS. Activation of visual cortex in 11 healthy subjects was studied. The authors underwent short and long stimulation, The relation between activation and postactivation signal was investigated after both durations of stimulation. RESULTS. Average postactivation signal after short stimulation was -1.71 +/- 2.66% and after long stimulation 0.82 +/- 1.59% (P less than or equal to 0.01). Significant ''undershoot'' was detected after short stimulation in the majority of cases, although this was typically absent after long stimulation. CONCLUSIONS The authors propose that ''undershoot'' is caused by decreased oxygen content in venous blood compared with the preactivation level and may reflect increased extraction of oxygen as a result of glycolytic metabolism, The absence of ''undershoot'' after longer stimulation suggests a gradual shift from uncoupling between regional cerebral blood flow and oxygen consumption toward a steady state.

Note: Article RP Friedland, Case Western Reserve Univ, Dept Neurol, 11100 Euclid Ave, Cleveland, OH 44106 USA

Keyword(s): functional magnetic resonance imaging; deoxyhemoglobin; oxidative metabolism; visual cortex; HUMAN VISUAL-CORTEX; POSITRON EMISSION TOMOGRAPHY; PHOTIC-STIMULATION; PHYSIOLOGICAL STIMULATION; SENSORY STIMULATION; BRAIN OXYGENATION; MOTOR CORTEX; CONTRAST; ACTIVATION; GLUCOSE

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