seX & whY Episode 5 Part 2: Stress Response

Nov 9, 2017

Show Notes for Podcast Five of Sex & Why

Host: Jeannette Wolfe

Topic: Stress Response

 

For Acute Care Medicine and Introduction to Sex and Gender Based Medicine CME Cruise Opportunity click here

 

Part 2 on biological sex differences in the stress response with special guest Justin Morgenstern

We started out with a discussion on different ways to frame potential sex and gender based research using a method described by  Dr. M McCarthy

A full discussion of this framework can also be found on my website

McCarthy MM et al, The Journal of Neuroscience: the official journal of the Society for Neuroscience. 2012;32(7):2241-2247.

There appears to be a significant amount of individual variation in how some individuals respond to and recover from similar stresses. Some of these differences may be influenced by our biological sex. Understanding how we react and respond to stress and how this may perhaps differ from other individuals around us may help us better communicate and lead under stressful situations.

Study #1

This was a follow up study to an infamous study the same team did three years before in which they looked at sex differences in reward collection on a computer balloon game (Balloon Analogue Risk Task or BART). In this game, players got 30 balloons and the farther they pumped them up the more points they got however, each balloon was also set to randomly pop somewhere between 1- 128 pumps and if the player popped their balloon before they cashed it in they lost points for that balloon. Study participants were randomized to control vs stress condition (placing hand in neutral versus ice water for 3 min) and then played the game. They found that in neutral conditions there was no significant difference in risk taking (number of pumps 39 for women versus 42 for men, but under stress women decreased their pumping to 32 while men increased to 48).

In this 2012 study, Lighthall’s group adjusted its protocol so that BART could now be played in an MRI scanner. Unfortunately, the new BART design subtly changed the game because now instead of going through 30 balloons, participants played the game for a set amount of time with unlimited balloons. This inadvertently added a second strategy to get lots of points as the new design allowed participants to get points by either pumping additional air into an individual balloon or rapidly moving through a greater number of balloons while pumping only a few pumps per balloon. Stress intervention was again either a cold or neutral temperature water bath and after submersion the researchers collected cortisol samples and scanned participants while they played the game.

Results- no difference in control conditions (room temp water) between men and women in number of balloon pumps or points earned

But under stress men acted more quickly and got increased rewards while women appeared to slow down their reaction time and decrease their rewards.

Men had higher baseline and stimulated cortisol but there was no difference b/w men and women in the amount of cortisol change between baseline and stressed condition.

Under basic non stress conditions- during the control testing it appeared that overall men and women utilized the same brain regions to complete the balloon task (i.e. suggesting that males and females approach the task by using similar neural strategies), however once stressed men and women seemed to use different areas of their brain. Men used their dorsal striatum and anterior insula more. Anterior insula has been associated with switching tasks from a riskier to a safer option (and in both sexes higher activity in this region correlated with higher collection rate) and the dorsal striatum is believed to be associated with obtaining predictable rewards and with integrating sensory, motor, cognitive and emotional signals.

Did not find that men had increased risk taking in this study but it may have been masked in that there was now a lower risk strategy available to them that still was associated with an increased reward (pumping balloon a small amount and quickly cashing in to get to next balloon).

Concept discussed is that under stress men may possible go into type one systemic thinking (automatic) while women may favor type 2 (deliberate cognitive inquiry).

Lighthall, N. R., Mather, M., & Gorlick, M. A. (2009). Acute stress increases sex differences in risk seeking in the balloon analogue risk task. PloS One, 4(7), e6002. https://doi.org/10.1371/journal.pone.0006002

Lighthall, N. R., Sakaki, M., Vasunilashorn, S., Nga, L., Somayajula, S., Chen, E. Y. Mather, M. (2012). Gender differences in reward-related decision processing under stress. Social Cognitive and Affective Neuroscience, 7(4), 476–84. https://doi.org/10.1093/scan/nsr026

Study #2: 

Goal to determine if:

• Under equal subjective sensations of stress (i.e. men and women objectively rate their subjective level of stress the same on a 1-10 point scale) do men and women use the same brain circuitry to process stress or do they use different circuitries.

What they did:

• Collect cognitive, psychiatric, and drug use assessments on 55 men and 41 women aged 19-50
  • Exclusions TBI, psychoactive meds, history of substance abuse, preg, DSM-IV mental health disorder and currently menstruating or oral contraceptive use (to try and mitigate additional hormonal influences)
• Over course of 2-3 sessions put them into a MRI scanner and asked them to visualize neutral or stress inducing images (this technique has previously been validated and involved the subjects own audiotaped accounts of stressful –rated as greater than 8 on 1-10 Likert scale- or neutral experience) which was later played back to them in MRI scanner
• Asked them to rank their level of stress
• Looked to see which areas of the brain lit up under different conditions

Results

Men and women appeared to have different strategies for guided visual tasks in general regardless of whether listening to neutral or stressful recordings:

Men:

More likely to light up areas associated with motor processing and action.

Caudate, midbrain, thalamus, and cingulate gyrus and cerebellum

Women:

More likely to light up areas associated with visual processing, verbal expression and emotional experience

            Right temporal gyrus, insula and occipital lobe

Women were also more likely to increase their HR regardless of condition (likely from having increased autonomic arousal- though other studies suggest that women have increased HR at baseline compared to men in general)

Under stress men and women had firing in opposite directions:

Men dampened while women increased firing in:

Dorsal Medial pre-frontal cortex, parietal lobes (including inferior parietal lobe and precuneus region) left temporal lobe, occipital area and cerebellum.

Believed functions of these different regions

Dorsal medial frontal cortex – executive functioning of cognitive control, self-awareness of emotional discomfort, strategic reasoning, and regulation

Precuneus- part of the parietal lobe associated with self-referential and self-consciousness

Inferior parietal lobe- cognitive appraisal and consideration of response strategies (also area often associated with mirror imaging)

Left temporal gyrus- processes verbal information

Occipital area- processes visual information

Cerebellum- besides coordinating motor movement also is involved in emotional and cognitive processing 

“Taken together, the observed differences in these regions suggest that men and women may differ in the extent to which they engage in verbal processing, visualization, self-referential thinking, and cognitive processing during the experience of stress and anxiety.”

They also suggest that under stress men may feel anxious due to “hypoactivity” while women may feel stress due to “hyperactivity” in above noted regions.

Conclusion:

• Men and women use different neural strategies under stress even with similarly reported stress levels

 This research is still clearly in its infancy but suggests that under stress some men, may turn down activity in areas of their brains involved in executive functioning and that this might increase their vulnerability to impulsivity. Conversely, under stress some women may actually turn up activity in these regions that could lead to excessive rumination and possibly depression. The authors then extrapolate their data to suggest that men and women might possibly benefit from different stress reduction techniques in that some men might benefit more from cognitive behavioral therapy which enhances frontal lobe firing and some women from mindful meditation which dampens it. 

Seo, D., Ahluwalia, A., Potenza, M. N., & Sinha, R. (2017). Gender Differences in Neural Correlates of Stress-Induced Anxiety. Journal of Neuroscience Research, 125, 115–125.

Study #3

This study literally looks at what conditions men and women might seek out increased physical interaction with their dog after an agility competition. The background here is that in 2000 Dr. SE Taylor questioned whether the flight of fight response which has classically been described as a “universal” stress response, was actually applicable to both males and females. She questioned how realistic it was for a female who might be physically smaller and less muscular than her male peer to successfully fight or run away from a potential attacker. She suggested an alternative response of “tend and befriend” which suggests that under stress that women may naturally migrate towards their children as well as others within their intimate circle with the belief that a larger group may offer protection and a pooling of resources. Additional support for this theory is the idea that oxytocin, which has receptors throughout the brain and is usually found in higher amounts in women, may be released during this affiliative behavior and help to dampen the physiological cortisol stress response.

This study was done to see if men and women seek out physical contact with another being (in this case their dog) in similar fashion when they are stressed. They chose to study human contact with a dog versus an interaction with another human to try and mitigate the influence of any “gender expectation” violations. Which in English means that if Rob would normally seek out Carol when he is stressed, he might decide not to do so in public (and in this case being videotaped) because he doesn’t want to appear “less masculine”. As public affection with one’s dog is considered less gender biased, the authors chose this interaction as a marker for affiliative behavior. 

What they did: Videotaped and took cortisol saliva levels from 93 men and  91 women after they had run their dog through a competitive agility course. Recording and samples were taken as participants waited for their official score (although subjectively most participants pretty much already knew whether or not their dog had scored high enough to move on.) The researchers measured cortisol levels and how much participants petted their dog while waiting for this score.

Results:

• 36 of results excluded because dogs did not finish course and were disqualified
• Overall there was no sex difference in total affiliative behavior
  • Of first 180 seconds of video tape women petted dog on average 27 seconds and men 25 seconds
• When men and women perceived they lost, their cortisol level increased more than those who perceived they had advanced.
• Differences occurred however as to when men and women were more likely to pet their dogs
  • Women petted them more when they sensed defeat- an additional 12 seconds compared to women who had won
  • Men petted them more when they sensed victory- an additional 7 seconds when compared to men who had lost

Conclusions: women sought out affiliative behavior when they lost, men sought it out when they won.

Justin and I use this paper as a discussion point as to understanding how two people may get exposed to the same stressor and respond quite differently and importantly how they sort of bounce back from a stressful situation may also differ. This paper suggests that emotional debriefing after stressful experiences may be more helpful to some individuals than others.

For more on the stress response please see Justin’s new post on First10EM

Sherman G, Rice L, Shuo Jin E, et al: (2017) Sex differences in cortisol’s regulation of affiliative behavior. Hormones and Behavior 92, 20- 28