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

Harper RM, Bandler R, Spriggs D, and Alger JR (2000) Lateralized and widespread brain activation during transient blood pressure elevation revealed by magnetic resonance imaging. J Comp Neurol 417:2 195–204.

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Abstract: The location and possible lateralization of structures mediating autonomic processing are not well-described in the human. Functional magnetic resonance imaging procedures were used to demonstrate signal changes in multiple brain sites during blood pressure challenges. Magnetic resonance signals in brain tissue were visualized with a 1.5 Tesla scanner in 11 healthy volunteers (22-37 years), by using echo-planar procedures. Images were collected during baseline states and three pressor 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-voxel basis to identify brain regions responsive to physiologic activation. Probability maps (P < 0.01) of voxel changes, with Bonferroni corrections for multiple comparisons, were determined, and amplitude of signal changes associated with significance maps were pseudocolored and overlaid on anatomic images. The time courses and extent of signal alterations in defined unilateral regions were followed and compared with changes in corresponding regions on the contralateral side. Pressor challenges elicited significant regional signal intensity changes within the orbitomedial prefrontal cortex, temporal cortex, amygdala, hippocampal formation, thalamus, and hypothalamus. Cerebellar, midbrain, and pontine areas were also recruited. Signal changes, especially at forebrain sites, were often highly lateralized. The findings indicate that (1) transient, behaviorally-coupled cardiovascular challenges elicit discrete activity changes over multiple brain sites, and (2) these activity changes, especially in specific prefrontal and temporal forebrain regions and cerebellum, are often expressed unilaterally, even to a bilateral challenge.

Keywords: pressor challenge; prefrontal cortex; hippocampus; cerebellum; Valsalva; pain

Context

• Like Harper et al., used cold challenges and Valsalva maneuver to assess changes in cerebral blood flow during transient hypertensive episodes in healthy volunteers. Widespread alterations were observed. One complexity is distinguishing alterations due simply to passive increases in local blood pressure and flux due to the increased systemic pressure from those that could be play a role in responding to the challenges. The lateralization of altered blood flow seen in some regions is unexpected and may reflect a more physiologic role.