Lateralized and widespread brain activation during transient blood pressure elevation revealed by magnetic resonance imaging

The location and possible lateralization of structures mediating autonomic processing are not well-described in the human. Functional magnetic resonan ce imaging procedures were used to demonstrate signal changes in multiple b rain sites during blood pressure challenges. Magnetic resonance signals in brain tissue were visualized with a 1.5 Tesla scanner in 11 healthy volunte ers (22-37 years), by using echo-planar procedures. Images were collected d uring baseline states and three presser challenges: cold application to the hand or forehead, and a Valsalva maneuver. Image values from experimental conditions were compared with corresponding baseline values on a voxel-by-v oxel basis to identify brain regions responsive to physiologic activation. Probability maps (P < 0.01) of voxel changes, with Bonferroni corrections f or multiple comparisons, were determined, and amplitude of signal changes a ssociated with significance maps were pseudocolored and overlaid on anatomi c images. The time courses and extent of signal alterations in defined unil ateral regions were followed and compared with changes in corresponding reg ions on the contralateral side. Presser challenges elicited significant reg ional signal intensity changes within the orbitomedial prefrontal cortex, t emporal cortex, amygdala, hippocampal formation, thalamus, and hypothalamus . Cerebellar, midbrain, and pontine areas were also recruited. Signal chang es, especially at forebrain sites, were often highly lateralized. The findi ngs indicate that (1) transient, behaviorally-coupled cardiovascular challe nges elicit discrete activity changes over multiple brain sites, and (2) th ese activity changes, especially in specific prefrontal and temporal forebr ain regions and cerebellum, are often expressed unilaterally, even to a bil ateral challenge. J. Comp. Neurol. 417:195-204, 2000. (C) 2000 Wiley-Liss, Inc.