1. Department of Neuroscience, Genentech, Inc., South San Francisco, California, U.S.A.
2. ^*Department of Radiology, Stanford University, Stanford, California, U.S.A.

Correspondence: N van Bruggen, Genentech, Inc., MS No. 72, 1 DNA Way, South San Francisco, CA 94080 U.S.A.

Received 20 August 1997; Revised 12 March 1998; Accepted 17 March 1998.

Abstract

Contrast-enhanced magnetic resonance imaging was used to produce high-resolution activation maps reflecting local changes in cerebral blood volume after a simple sensory stimulus. Activation of the forelimb region of the somatosensory cortex was performed in -chloralose-anaesthetized rats with an electrical stimulus (5 V, 3 Hz) delivered through needle electrodes placed subcutaneously on the left forelimb. A gradient echo magnetic resonance imaging sequence, sensitive to changes in the relative amount of deoxyhemoglobin within the cerebral vasculature, produced a 4.05% 1.69% increase in signal intensity. This effect was enhanced with an injection of an intravascular iron oxide contrast agent (Combidex, Advanced Magnetics), resulting in a 9.11% 1.52% decrease in signal intensity.