HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 100/1/266    most recent 00588.2005v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Macefield, V. G. Articles by Henderson, L. A. Search for Related Content PubMed PubMed Citation Articles by Macefield, V. G. Articles by Henderson, L. A.

Neural sites involved in the sustained increase in muscle sympathetic nerve activity induced by inspiratory capacity apnea: a fMRI study

¹Prince of Wales Medical Research Institute and University of New South Wales, and ²Department of Anatomy and Histology, University of Sydney, Sydney, New South Wales, Australia

Submitted 19 May 2005 ; accepted in final form 22 August 2005

A maximal inspiratory breath hold (inspiratory capacity apnea) against a closed glottis evokes a large and sustained increase in muscle sympathetic nerve activity (MSNA). Because of its dependence on a high intrathoracic pressure, it has been suggested that this maneuver causes unloading of the low-pressure baroreceptors, known to increase MSNA. To determine the central origins of this sympathoexcitation, we used functional magnetic resonance imaging to define the loci and time course of activation of different brain areas. We hypothesized that, as previously shown for the Valsalvsa maneuver, discrete but widespread regions of the brain would be involved. In 15 healthy human subjects, a series of 90 gradient echo echo-planar image sets was collected during three consecutive 40-s inspiratory capacity apneas using a 3-T scanner. Global signal intensity changes were calculated and subsequently removed by using a detrending technique, which eliminates the global signal component from each voxel's signal intensity change. Whole brain correlations between changes in signal intensity and the known pattern of MSNA during the maneuver were performed on a voxel-by-voxel basis, and significant changes were determined by using a random-effects analysis procedure (P < 0.01, uncorrected). Significant signal increases emerged in multiple areas, including the rostral lateral medulla, cerebellar nuclei, anterior insula, dorsomedial hypothalamus, anterior cingulate, and lateral prefrontal cortexes. Decreases in signal intensity occurred in the dorsomedial and caudal lateral medulla, cerebellar cortex, hippocampus, and posterior cingulate cortex. Given that many of these sites have roles in cardiovascular control, the sustained increase in MSNA during an inspiratory capacity apnea is likely to originate from a distributed set of discrete areas.

cardiopulmonary receptors; sympathetic activity; paraventricular nucleus; medulla

This article has been cited by other articles:

				S. W. Wong, D. S. Kimmerly, N. Masse, R. S. Menon, D. F. Cechetto, and J. K. Shoemaker Sex differences in forebrain and cardiovagal responses at the onset of isometric handgrip exercise: a retrospective fMRI study J Appl Physiol, October 1, 2007; 103(4): 1402 - 1411. [Abstract] [Full Text] [PDF]

				D. S. Kimmerly, S. W. Wong, D. Salzer, R. Menon, and J. K. Shoemaker Forebrain regions associated with postexercise differences in autonomic and cardiovascular function during baroreceptor unloading Am J Physiol Heart Circ Physiol, July 1, 2007; 293(1): H299 - H306. [Abstract] [Full Text] [PDF]