Summary: Researchers discover structural and functional differences in the insula between men and women.
While measuring brain activity with magnetic resonance imaging during blood pressure trials, UCLA researchers found that men and women had opposite responses in the right front of the insular cortex, a part of the brain integral to the experience of emotions, blood pressure control and self-awareness.
The insular cortex has five main parts called gyri serving different roles. The researchers found that the blood pressure response in the front right gyrus showed an opposite pattern in men and women, with men showing a greater right-sided activation in the area while the women showed a lower response.
“This is such a critical brain area and we hadn’t expected to find such strong differences between men and women’s brains,” said Paul Macey, the study’s lead author. “This region, the front-right insula, is involved with stress and keeping heart rate and blood pressure high. It’s possible the women had already activated this region because of psychological stress, so that when they did the physical test in the study, the brain region could not activate any more. However, it’s also possible that this region is wired differently in men and women.”
“We have always thought that the ‘normal’ pattern was for this right-front insula region to activate more than other areas, during a task that raises blood pressure,” added Macey. “However, since most earlier studies were in men or male animals, it looks like this ‘normal’ response was only in men. The healthy response in women seems to be a lower right-sided activation.”
Most studies on differences in brain functions between men and women have looked at psychological performance.
In previous studies, the UCLA researchers had seen differences in heart rate and blood brain flow during blood pressure changes in men and women with obstructive sleep apnea and wanted to see if cardiovascular responses in brain areas were different in healthy men and women.
In this study, researchers from the UCLA School of Nursing used the Valsalva maneuver — during which participants breathe hard out through a very small tube to raise blood pressure — to measure brain activity as it controls the blood pressure change.
“This raises several questions for us, such as why is there a difference in brain pattern and might it reflect differences in health issues for men and women, particularly in cardiovascular disease variations,” Macey said.
To find the answers, further study on this difference will be needed to gain a better understanding of susceptibility to disease, efficacy of drugs and even the course of normal development among all individuals, not just between men and women.
“We believe that differences in the structure and function of the insula in men and women might contribute to different clinical symptoms in some medical disorders,” Macey said.
About this neuroscience research article
The author of the study is Macey, an associate professor in the UCLA School of Nursing.
Funding: The study was funded by a grant from the National Institute of Nursing Research, NR013693.
Source: Laura Perry – UCLA Image Source: This NeuroscienceNews.com image is in the public domain. Original Research: Full open access research for “Sex Differences in Insular Cortex Gyri Responses to the Valsalva Maneuver” by Paul M. Macey, Nicholas S. Rieken, Rajesh Kumar, Jennifer A. Ogren, Holly R. Middlekauff, Paula Wu, Mary A. Woo and Ronald M. Harper in Frontiers in Neurology. Published online June 9 2016 doi:10.3389/fneur.2016.00087
Cite This NeuroscienceNews.com Article
[cbtabs][cbtab title=”MLA”]UCLA. “New Evidence That Male and Female Brains Are Wired Differently.” NeuroscienceNews. NeuroscienceNews, 13 July 2016. <https://neurosciencenews.com/neuroscience-insula-sex-differences-4680/>.[/cbtab][cbtab title=”APA”]UCLA. (2016, July 13). New Evidence That Male and Female Brains Are Wired Differently. NeuroscienceNew. Retrieved July 13, 2016 from https://neurosciencenews.com/neuroscience-insula-sex-differences-4680/[/cbtab][cbtab title=”Chicago”]UCLA. “New Evidence That Male and Female Brains Are Wired Differently.” https://neurosciencenews.com/neuroscience-insula-sex-differences-4680/ (accessed July 13, 2016).[/cbtab][/cbtabs]
Sex Differences in Insular Cortex Gyri Responses to the Valsalva Maneuver
Sex differences in autonomic regulation may underlie cardiovascular disease variations between females and males. One key autonomic brain region is the insular cortex, which typically consists of five main gyri in each hemisphere, and shows a topographical organization of autonomic function across those gyri. The present study aims to identify possible sex differences in organization of autonomic function in the insula. We studied brain functional magnetic resonance imaging (fMRI) responses to a series of four 18-s Valsalva maneuvers in 22 healthy females (age ± SD: 50.0 ± 7.9 years) and 36 healthy males (45.3 ± 9.2 years). Comparisons of heart rate (HR) and fMRI signals were performed with repeated measures ANOVA (threshold P < 0.05 for all findings). All subjects achieved the target 30 mmHg expiratory pressure for all challenges. Typical HR responses were elicited by the maneuver, including HR increases from ~4 s into the strain period (Phase II) and rapid declines to below baseline 5–10 s, following strain release (Phase IV). Small, but significant, sex differences in HR percent change occurred during the sympathetic-dominant Phase II (female < male) and parasympathetic-dominant Phase IV (female > male, i.e., greater undershoot in males). The insular cortices showed similar patterns in all gyri, with greater signal decreases in males than females. Both sexes exhibited an anterior–posterior topographical organization of insular responses during Phase II, with anterior gyri showing higher responses than more posterior gyri. The exception was the right anterior-most gyrus in females, which had lower responses than the four other right gyri. Responses were lateralized, with right-sided dominance during Phase II in both sexes, except the right anterior-most gyrus in females, which showed lower responses than the left. The findings confirm the anterior and right-sided sympathetic dominance of the insula. Although sex differences were prominent in response magnitude, organization differences between males and females were limited to the right anterior-most gyrus, which showed a lower fMRI response in females vs. males (and vs. other gyri in females). The sex differences suggest a possible differing baseline state of brain physiology or tonic functional activity between females and males, especially in the right anterior-most gyrus.
“Sex Differences in Insular Cortex Gyri Responses to the Valsalva Maneuver” by Paul M. Macey, Nicholas S. Rieken, Rajesh Kumar, Jennifer A. Ogren, Holly R. Middlekauff, Paula Wu, Mary A. Woo and Ronald M. Harper in Frontiers in Neurology. Published online June 9 2016 doi:10.3389/fneur.2016.00087