Abstract
BackgroundCardiovascular disease varies between sexes, suggesting male-female autonomic control differences. Insular gyri help coordinate autonomic regulation and show a sex-dependent response to a sympathetic challenge.MethodsWe examined sex-related insular gyral responses to a short static handgrip exercise challenge eliciting parasympathetic withdrawal with functional magnetic resonance imaging (fMRI) during four 16-s challenges (80% maximum strength) in 23 healthy females (age; mean ± std 50 ± 8 years) and 40 males (46 ± 9 years). Heart rate (HR) and fMRI signals were compared with repeated measures ANOVA (P < 0.05). Additional analyses were performed with age and age interactions, as well as right-handed only subjects.ResultsFemales showed higher resting HR than males, but smaller percent HR change increases to the challenges. All gyri showed fMRI patterns concurrent with an HR peak and decline to baseline. fMRI signals followed an anterior-posterior organization in both sexes, but lateralization varied by gyri and sex. All subjects showed greater signals in the anterior vs. posterior gyri (females 0.3%, males 0.15%). The middle gyri showed no lateralization in females but left-sided dominance in males (0.1%). The posterior gyri showed greater left than right activation in both sexes. The anterior-most gyri exhibited a prominent sex difference, with females showing a greater right-sided activation (0.2%) vs. males displaying a greater left-sided activation (0.15%). Age and handedness affected a minority of findings but did not alter the overall pattern of results.ConclusionsThe anterior insula plays a greater role in cardiovascular regulation than posterior areas during a predominantly parasympathetic withdrawal challenge, with opposite lateralization between sexes. In females, the left anterior-most gyrus responded distinctly from other regions than males. Those sex-specific structural and functional brain patterns may contribute over time to variations in cardiovascular disease between the sexes.
Highlights
Cardiovascular disease varies between sexes, suggesting male-female autonomic control differences
The present study follows from the Valsalva findings to assess responses to a brief static handgrip exercise challenge, which increases blood pressure and heart rate, most likely through vagal withdrawal, without notable increase in sympathetic activity as measured by muscle sympathetic nerve activity (MSNA), at least during brief (
Differentiating which arm of the autonomic nervous system, sympathetic or parasympathetic, plays dominant roles in challenges is a significant issue in formulating care for pathologic cardiovascular and other conditions where expression of symptoms may substantially differ between males and females
Summary
Cardiovascular disease varies between sexes, suggesting male-female autonomic control differences. In contrast with other insular regions in females and males, the right ASG showed a lower response on the right over the left side This sex-specific altered insular response may be a characteristic of sympathetic activation, as occurs during the Valsalva maneuver, or may be coincident with any heart rate increase. Differentiating which arm of the autonomic nervous system, sympathetic or parasympathetic, plays dominant roles in challenges is a significant issue in formulating care for pathologic cardiovascular and other conditions where expression of symptoms may substantially differ between males and females Brain areas serving those separate components may be subject to injury or otherwise affected between sexes in the pathologic conditions, and interventions must consider those possibilities
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