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Jovialis
03-05-18, 16:02
Researchers at the Stanford University School of Medicine have identified two adjacent clusters of nerve cells in the brains of mice whose activation levels upon sighting a visual threat spell the difference between a timid response and a bold or even fierce one.


Located smack-dab in the middle of the brain, these clusters, or nuclei, each send signals to a different area of the brain, igniting opposite behaviors in the face of a visual threat. By selectively altering the activation levels of the two nuclei, the investigators could dispose the mice to freeze or duck into a hiding space, or to aggressively stand their ground, when approached by a simulated predator.


People's brains probably possess equivalent circuitry, said Andrew Huberman, PhD, associate professor of neurobiology and of ophthalmology. So, finding ways to noninvasively shift the balance between the signaling strengths of the two nuclei in advance of, or in the midst of, situations that people perceive as threatening may help people with excessive anxiety, phobias or post-traumatic stress disorder lead more normal lives.


"This opens the door to future work on how to shift us from paralysis and fear to being able to confront challenges in ways that make our lives better," said Huberman, the senior author of a paper describing the experimental results. It will be published online May 2 in Nature. Graduate student Lindsey Salay is the lead author.

Perilous life of a mouse

There are plenty of real threats in a mouse's world, and the rodents have evolved to deal with those threats as best they can. For example, they're innately afraid of aerial predators, such as a hawk or owl swooping down on them. When a mouse in an open field perceives a raptor overhead, it must make a split-second decision to either freeze, making it harder for the predator to detect; duck into a shelter, if one is available; or run for its life.


To learn how brain activity changes in the face of such a visual threat, Salay simulated a looming predator's approach using a scenario devised some years ago by neurobiologist Melis Yilmaz Balban, PhD, now a postdoctoral scholar in Huberman's lab. It involves a chamber about the size of a 20-gallon fish tank, with a video screen covering most of its ceiling. This overhead screen can display an expanding black disc simulating a bird-of-prey's aerial approach.


Looking for brain regions that were more active in mice exposed to this "looming predator" than in unexposed mice, Salay pinpointed a structure called the ventral midline thalamus, or vMT.

Salay mapped the inputs and outputs of the vMT and found that it receives sensory signals and inputs from regions of the brain that register internal brain states, such as arousal levels. But in contrast to the broad inputs the vMT receives, its output destination points were remarkably selective. The scientists traced these outputs to two main destinations: the basolateral amygdala and the medial prefrontal cortex. Previous work has tied the amygdala to the processing of threat detection and fear, and the medial prefrontal cortex is associated with high-level executive functions and anxiety.

Further inquiry revealed that the nerve tract leading to the basolateral amygdala emanates from a nerve-cell cluster in the vMT called the xiphoid nucleus. The tract that leads to the medial prefrontal cortex, the investigators learned, comes from a cluster called the nucleus reuniens, which snugly envelopes the xiphoid nucleus.

Next, the investigators selectively modified specific sets of nerve cells in mice's brains so they could stimulate or inhibit signaling in these two nerve tracts. Exclusively stimulating xiphoid activity markedly increased mice's propensity to freeze in place in the presence of a perceived aerial predator. Exclusively boosting activity in the tract running from the nucleus reuniens to the medial prefrontal cortex in mice exposed to the looming-predator stimulus radically increased a response seldom seen under similar conditions in the wild or in previous open-field experiments: The mice stood their ground, right out in the open, and rattled their tails, an action ordinarily associated with aggression in the species.

This "courageous" behavior was unmistakable, and loud, Huberman said. "You could hear their tails thumping against the side of the chamber. It's the mouse equivalent of slapping and beating your chest and saying, 'OK, let's fight!'" The mice in which the nucleus reuniens was stimulated also ran around more in the chamber's open area, as opposed to simply running toward hiding places. But it wasn't because nucleus reuniens stimulation put ants in their pants; in the absence of a simulated looming predator, the same mice just chilled out.

In another experiment, the researchers showed that stimulating mice's nucleus reuniens for 30 seconds before displaying the "looming predator" induced the same increase in tail rattling and running around in the unprotected part of the chamber as did vMT stimulation executed concurrently with the display. This suggests, Huberman said, that stimulating nerve cells leading from the nucleus reunions to the prefrontal cortex induces a shift in the brain's internal state, predisposing mice to act more boldly.

Another experiment pinpointed the likely nature of that internal-state shift: arousal of the autonomic nervous system, which kick-starts the fight, flight or freeze response. Stimulating either the vMT as a whole or just the nucleus reuniens increased the mice's pupil diameter—a good proxy of autonomic arousal.

On repeated exposures to the looming-predator mockup, the mice became habituated. Their spontaneous vMT firing diminished, as did their behavioral responses. This correlates with lowered autonomic arousal levels.

Human brains harbor a structure equivalent to the vMT, Huberman said. He speculated that in people with phobias, constant anxiety or PTSD, malfunctioning circuitry or traumatic episodes may prevent vMT signaling from dropping off with repeated exposure to a stress-inducing situation. In other experiments, his group is now exploring the efficacy of techniques, such as deep breathing and relaxation of visual fixation, in adjusting the arousal states of people suffering from these problems. The thinking is that reducing vMT signaling in such individuals, or altering the balance of signaling strength from their human equivalents of the xiphoid nucleus and nucleus reuniens may increase their flexibility in coping with stress.


https://medicalxpress.com/news/2018-05-scientists-courage-brain.html


A midline thalamic circuit determines reactions to visual threat


How our internal state is merged with our visual perception of an impending threat to drive an adaptive behavioural response is not known. Mice respond to visual threats by either freezing or seeking shelter. Here we show that nuclei of the ventral midline thalamus (vMT), the xiphoid nucleus (Xi) and nucleus reuniens (Re), represent crucial hubs in the network controlling behavioural responses to visual threats. The Xi projects to the basolateral amygdala to promote saliency-reducing responses to threats, such as freezing, whereas the Re projects to the medial prefrontal cortex (Re→mPFC) to promote saliency-enhancing, even confrontational responses to threats, such as tail rattling. Activation of the Re→mPFC pathway also increases autonomic arousal in a manner that is rewarding. The vMT is therefore important for biasing how internal states are translated into opposing categories of behavioural responses to perceived threats. These findings may have implications for understanding disorders of arousal and adaptive decision-making, such as phobias, post-traumatic stress and addictions.


https://www.nature.com/articles/s41586-018-0078-2

Angela
03-05-18, 19:10
Researchers at the Stanford University School of Medicine have identified two adjacent clusters of nerve cells in the brains of mice whose activation levels upon sighting a visual threat spell the difference between a timid response and a bold or even fierce one.


Located smack-dab in the middle of the brain, these clusters, or nuclei, each send signals to a different area of the brain, igniting opposite behaviors in the face of a visual threat. By selectively altering the activation levels of the two nuclei, the investigators could dispose the mice to freeze or duck into a hiding space, or to aggressively stand their ground, when approached by a simulated predator.


People's brains probably possess equivalent circuitry, said Andrew Huberman, PhD, associate professor of neurobiology and of ophthalmology. So, finding ways to noninvasively shift the balance between the signaling strengths of the two nuclei in advance of, or in the midst of, situations that people perceive as threatening may help people with excessive anxiety, phobias or post-traumatic stress disorder lead more normal lives.


"This opens the door to future work on how to shift us from paralysis and fear to being able to confront challenges in ways that make our lives better," said Huberman, the senior author of a paper describing the experimental results. It will be published online May 2 in Nature. Graduate student Lindsey Salay is the lead author.

Perilous life of a mouse

There are plenty of real threats in a mouse's world, and the rodents have evolved to deal with those threats as best they can. For example, they're innately afraid of aerial predators, such as a hawk or owl swooping down on them. When a mouse in an open field perceives a raptor overhead, it must make a split-second decision to either freeze, making it harder for the predator to detect; duck into a shelter, if one is available; or run for its life.


To learn how brain activity changes in the face of such a visual threat, Salay simulated a looming predator's approach using a scenario devised some years ago by neurobiologist Melis Yilmaz Balban, PhD, now a postdoctoral scholar in Huberman's lab. It involves a chamber about the size of a 20-gallon fish tank, with a video screen covering most of its ceiling. This overhead screen can display an expanding black disc simulating a bird-of-prey's aerial approach.


Looking for brain regions that were more active in mice exposed to this "looming predator" than in unexposed mice, Salay pinpointed a structure called the ventral midline thalamus, or vMT.

Salay mapped the inputs and outputs of the vMT and found that it receives sensory signals and inputs from regions of the brain that register internal brain states, such as arousal levels. But in contrast to the broad inputs the vMT receives, its output destination points were remarkably selective. The scientists traced these outputs to two main destinations: the basolateral amygdala and the medial prefrontal cortex. Previous work has tied the amygdala to the processing of threat detection and fear, and the medial prefrontal cortex is associated with high-level executive functions and anxiety.

Further inquiry revealed that the nerve tract leading to the basolateral amygdala emanates from a nerve-cell cluster in the vMT called the xiphoid nucleus. The tract that leads to the medial prefrontal cortex, the investigators learned, comes from a cluster called the nucleus reuniens, which snugly envelopes the xiphoid nucleus.

Next, the investigators selectively modified specific sets of nerve cells in mice's brains so they could stimulate or inhibit signaling in these two nerve tracts. Exclusively stimulating xiphoid activity markedly increased mice's propensity to freeze in place in the presence of a perceived aerial predator. Exclusively boosting activity in the tract running from the nucleus reuniens to the medial prefrontal cortex in mice exposed to the looming-predator stimulus radically increased a response seldom seen under similar conditions in the wild or in previous open-field experiments: The mice stood their ground, right out in the open, and rattled their tails, an action ordinarily associated with aggression in the species.

This "courageous" behavior was unmistakable, and loud, Huberman said. "You could hear their tails thumping against the side of the chamber. It's the mouse equivalent of slapping and beating your chest and saying, 'OK, let's fight!'" The mice in which the nucleus reuniens was stimulated also ran around more in the chamber's open area, as opposed to simply running toward hiding places. But it wasn't because nucleus reuniens stimulation put ants in their pants; in the absence of a simulated looming predator, the same mice just chilled out.

In another experiment, the researchers showed that stimulating mice's nucleus reuniens for 30 seconds before displaying the "looming predator" induced the same increase in tail rattling and running around in the unprotected part of the chamber as did vMT stimulation executed concurrently with the display. This suggests, Huberman said, that stimulating nerve cells leading from the nucleus reunions to the prefrontal cortex induces a shift in the brain's internal state, predisposing mice to act more boldly.

Another experiment pinpointed the likely nature of that internal-state shift: arousal of the autonomic nervous system, which kick-starts the fight, flight or freeze response. Stimulating either the vMT as a whole or just the nucleus reuniens increased the mice's pupil diameter—a good proxy of autonomic arousal.

On repeated exposures to the looming-predator mockup, the mice became habituated. Their spontaneous vMT firing diminished, as did their behavioral responses. This correlates with lowered autonomic arousal levels.

Human brains harbor a structure equivalent to the vMT, Huberman said. He speculated that in people with phobias, constant anxiety or PTSD, malfunctioning circuitry or traumatic episodes may prevent vMT signaling from dropping off with repeated exposure to a stress-inducing situation. In other experiments, his group is now exploring the efficacy of techniques, such as deep breathing and relaxation of visual fixation, in adjusting the arousal states of people suffering from these problems. The thinking is that reducing vMT signaling in such individuals, or altering the balance of signaling strength from their human equivalents of the xiphoid nucleus and nucleus reuniens may increase their flexibility in coping with stress.


https://medicalxpress.com/news/2018-05-scientists-courage-brain.html

I'd be leery of making people too aggressive, though.

I generally think they're onto something, however. I'm normally very easy going in terms of my relationships with other people. If they want to drive, take their route, pick the restaurant, the movie, whatever, I'm likely to just go with the flow unless it becomes completely obnoxious.

That's not how I respond to threat, though. Very shortly after I moved to the City, some jerk in the middle of Grand Central Station started to pull my bag off my shoulder. I don't remember thinking anything through, but I held on for dear life with both hands and screamed my bloody head off. After a few seconds he let go and took off down the maze of gates. If I'd actually thought about it, that wasn't the safest response, but as I said, I wasn't thinking.

I've also had a few encounters with violent people during work hours. My overwhelming response isn't fear: it's rage. I wouldn't have any hesitation at all about standing my ground and shooting some SOB if I had to do it. You can't live in fear your whole life.

That doesn't mean I don't have my fears. I've always been extremely anxious or fearful where the health of my loved ones is concerned. That's different.

Jovialis
03-05-18, 19:32
I'd be leery of making people too aggressive, though.
I generally think they're onto something, however. I'm normally very easy going in terms of my relationships with other people. If they want to drive, take their route, pick the restaurant, the movie, whatever, I'm likely to just go with the flow unless it becomes completely obnoxious.
That's not how I respond to threat, though. Very shortly after I moved to the City, some jerk in the middle of Grand Central Station started to pull my bag off my shoulder. I don't remember thinking anything through, but I held on for dear life with both hands and screamed my bloody head off. After a few seconds he let go and took off down the maze of gates. If I'd actually thought about it, that wasn't the safest response, but as I said, I wasn't thinking.
I've also had a few encounters with violent people during work hours. My overwhelming response isn't fear: it's rage. I wouldn't have any hesitation at all about standing my ground and shooting some SOB if I had to do it. You can't live in fear your whole life.
That doesn't mean I don't have my fears. I've always been extremely anxious or fearful where the health of my loved ones is concerned. That's different.

Same here, if it came down to it I would defend myself however necessary. There's a lot of confrontational situations I've been in around the area where I work. Especially on the drive to work during rush hour. When I was younger, there were some incidents too. I find that in the middle of those situations, the adrenaline is running high, which makes me focus on more instinct than thinking about the situation.

davef
03-05-18, 19:38
Yes Jovialis. I get annoyed when these arm chair quarterbacks thinking they're James Bond say things like "if I were in that situation I would've (insert well thought out tactic here), man what an idiot" when it's much easier to plan things out when you're comfy and in front of the computer.

Angela
03-05-18, 20:14
Yes Jovialis. I get annoyed when these arm chair quarterbacks thinking they're James Bond say things like "if I were in that situation I would've (insert well thought out tactic here), man what an idiot" when it's much easier to plan things out when you're comfy and in front of the computer.

I didn't report what I would do, but what I DID. Also, you have no idea what situations I've encountered in my line of work and how I reacted. Not everyone works at a cubicle for a computer company. Some of us have to get our hands dirtier than that. It's not a good idea to make assumptions about other people's life experiences.

davef
03-05-18, 21:36
I didn't report what I would do, but what I DID. Also, you have no idea what situations I've encountered in my line of work and how I reacted. Not everyone works at a cubicle for a computer company. Some of us have to get our hands dirtier than that. It's not a good idea to make assumptions about other people's life experiences.
I never made any assumption about you or your experiences. I was adding to what Jovialis said about how adrenaline and fear can lead to taking a more instinctive approach.

Angela
03-05-18, 22:38
I never made any assumption about you or your experiences. I was adding to what Jovialis said about how adrenaline and fear can lead to taking a more instinctive approach.

That's very true, Davef. Fighting is not always the best choice rationally, but instinct does take over for some people.

Jovialis
04-05-18, 03:59
Yes Jovialis. I get annoyed when these arm chair quarterbacks thinking they're James Bond say things like "if I were in that situation I would've (insert well thought out tactic here), man what an idiot" when it's much easier to plan things out when you're comfy and in front of the computer.

What are you talking about? You think people don't prepare for conflict? Do you think this about martial artists, or the military as well?

davef
04-05-18, 04:21
What are you talking about? You think people don't prepare for conflict? Do you think this about martial artists, or the military as well?
Of course not. They're highly trained to handle situations like that and know what to do from the get go. I'm referring to those who aren't and cannot rely on prior training and have to "think of something fast" without having the time to strategize (it's tough to think when fight or flight kicks in). I've noticed that when some people catch them not taking the smartest approach, they hurl insults without knowing it's easier to think of the best solution when you're not under that kind of pressure.

Salento
04-05-18, 04:53
Theoretically In the Military is the Discipline acquired through Training that instill in to Soldiers a sense of Self-Confidence and by association Courage. ( or that’s the idea ).

@Davef “Tactical Retreat” fancy word for: RuuuN !
We Shall regroup Later! :)

Angela
04-05-18, 15:11
Fwiw, one of the biggest problems with rape is that a lot of women just freeze in fear. That's the absolutely wrong response. You should scream your head off. For one thing, someone might hear and either come to your aid or call for help. For another thing, it might frighten the rapist that someone will come and they'll take off. Also important, to prove rape you often need proof of injury. What women sometimes fear is that if they resist they'll be killed. If he plans to kill you that's already in the plan. Obviously, if he has a gun pointed at you or a knife at your throat it's a different story, but still you should try within those first minutes to get away.

This isn't about training, but about being told what to do, although I think a good self-defense course is something that would benefit most people.

Every situation is different.

If someone with an AK47 comes into a school, or some deranged husband comes to a courthouse to shoot his wife or her divorce lawyer, unless you're armed as well, hiding is probably your best option. Then, you have to hope that some people have the presence of mind and guts to tackle him when he's re-loading. Since these guys are never Rambo, it's doable.

Also fwiw, soldiers I've heard speak about this still say they experience fear. It's just that the fear is not incapacitating. A lot of that, of course, is training, but all the training in the world wouldn't be enough for some people.