Death metal bat

My favorite wild animals are bats.

I think the flying fox -- a large diurnal species of fruit bat -- has got to be one of the coolest animals in the world.  Think about how amazing it would be, being a flying fox.  You have great big wings and can fly anywhere you want, you get to eat figs and dates all day, and you're cute as the dickens.  What could be better than that?

Fruit-eating sky puppies, is what they are.

[Image licensed under the Creative Commons Trikansh sharma, Eye contact with flying fox, CC0 1.0]

Unfortunately, bats in general have gotten a bad name, even though they're unequivocally beneficial.  (The insectivorous kinds can eat up to a thousand small flying insects -- including disease-carrying mosquitoes -- in an hour.)   The negative reputation comes from two sources: first, an association with drinking blood (only three out of the thousand species of bats do that; all three live in South America and almost never bite humans); and second, that they carry rabies (which can happen -- but so do raccoons, foxes, skunks, feral cats and dogs, and even deer).

Bats are good guys.  They're also incredibly cool.  I did a piece last year about the wild adaptations for echolocating in nocturnal bats, an ability I still find mind-boggling.  Which is why I was so psyched to run across a paper this week in PLOS-Biology about the fact that their ability to produce such an amazing array of sounds is due to the same feature death metal singers use to get their signature growl. 

In "Bats Expand Their Vocal Range By Recruiting Different Laryngeal Structures for Echolocation and Social Communication," biologists Jonas Håkonsson, Cathrine Mikkelsen, Lasse Jakobsen, and Coen Elemans, of the University of Southern Denmark, write:

Echolocating bats produce very diverse vocal signals for echolocation and social communication that span an impressive frequency range of 1 to 120 kHz or 7 octaves.  This tremendous vocal range is unparalleled in mammalian sound production and thought to be produced by specialized laryngeal vocal membranes on top of vocal folds.  However, their function in vocal production remains untested. By filming vocal membranes in excised bat larynges (Myotis daubentonii) in vitro with ultra-high-speed video (up to 250,000 fps) and using deep learning networks to extract their motion, we provide the first direct observations that vocal membranes exhibit flow-induced self-sustained vibrations to produce 10 to 95 kHz echolocation and social communication calls in bats.  The vocal membranes achieve the highest fundamental frequencies (fo’s) of any mammal, but their vocal range is with 3 to 4 octaves comparable to most mammals.  We evaluate the currently outstanding hypotheses for vocal membrane function and propose that most laryngeal adaptations in echolocating bats result from selection for producing high-frequency, rapid echolocation calls to catch fast-moving prey.  Furthermore, we show that bats extend their lower vocal range by recruiting their ventricular folds—as in death metal growls—that vibrate at distinctly lower frequencies of 1 to 5 kHz for producing agonistic social calls.  The different selection pressures for echolocation and social communication facilitated the evolution of separate laryngeal structures that together vastly expanded the vocal range in bats.

NPR did a story on the research, and followed it up by talking to some death metal singers, all of whom were pretty fascinated to find out bats can do it, too.  "In a [masochistic] sort of way ... I think that when I can feel that my vocal cords are getting kind of shredded or beat up, that it sounds better," said Chase Mason, lead singer of the band Gatecreeper.  "You know, like, if there's a little taste of blood in the back of my throat, I think that I'm doing a good job...  A lot of people will compare you to sounding like a bear or something like that, like an animal growling or roaring even... I think it's cool.  It's very dark and gothic.  The imagery of a bat is always associated with the darker sort of things, like vampires and stuff.  So it definitely makes sense."

I'm still more favoring the Sky Puppy model of bats, but hey, I'm not arguing with a guy who can make noises like Chase Mason can.

In any case, add one more thing to the "cool" column for bats, which was pretty lengthy already.  It's incredible that however much we learn about nature, there are always ways it'll come back and surprise you.  That's why if you have a curious side, learn some science -- you'll never be short of new things to wonder at.

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There's the rub

I'm currently benched from one of my favorite activities: running.

I have, once again, injured my back.  Four years ago, I got sciatica -- inflammation of the sciatic nerve -- that sidelined me for almost a year before it really had resolved enough that I could run again.  It's returned, probably due to my hefting around twenty-five kilogram bags of rock salt for our water softener a couple of weeks ago.  Like last time, there was no "uh-oh" moment, when I felt a twinge or a jolt; but the next day, I went for an easy four-mile run and ended up limping my way home.

At least it's on the opposite side this time, although I'm not honestly sure it's any better to injure new and different body parts than it is to keep re-injuring the same one over and over.

Seriously discouraging, mostly because I'm anticipating this thing once again taking a long time to heal.  I work with a kickass trainer, Kevin, who has informed me that he is not going to let me give up.  He's had issues with his back as well, so he knows the drill -- and knows things to do that will help.  Stretching, heating pads, using a TENS (trans-cutaneous electrical nerve stimulation) unit.  I've had suggestions from other people -- chiropractic and acupuncture topping the list -- but I've hesitated to go that direction, because from what I've read, neither one has been shown effective for treating injuries, and in fact there are cases of chiropractic adjustment making things worse.

So I'm following what Kevin says to do, and I'm seeing some gradual improvement.  Not nearly as fast as I'd like, but still, progress is progress.  I am not a patient person, and I'm very ready to get myself out there racing again.

This is why I was very interested to read some research out of Harvard University this week supporting the claim that another commonly-used recovery technique -- massage -- apparently does have a positive therapeutic effect, beyond just feeling good.  A team led by Bo Ri Seo, of the Harvard's Wyss Institute for Biologically-Inspired Engineering, did an experiment with mice that not only showed massage speeds up healing, but gives a clue as to why it works.

Neutrophils are a type of white blood cell associated with inflammation; inflamed tissue produces chemical signals called cytokines, which acts to increase blood flow (thus the swelling associated with inflammation) and attract neutrophils to clear out the damaged tissue.  So this response is critical for initiating healing both in cases of infection and in mechanical injuries.

Which is all very well, up to a point.  "Neutrophils are known to kill and clear out pathogens and damaged tissue, but in this study we identified their direct impacts on muscle progenitor cell behaviors," said study co-author Stephanie McNamara.  "While the inflammatory response is important for regeneration in the initial stages of healing, it is equally important that inflammation is quickly resolved to enable the regenerative processes to run its full course."

The team worked with mice, and developed a little "massage gun" to exert regular, rhythmic pressure on their tiny muscles.  What they found was that the mechanical compression from a massage forces out both the neutrophils and the cytokines from damaged tissue, allowing them to heal not only faster, but stronger.  The rebuilt muscle tissue had thicker fibers, and also more fibers of the type involved with greater force production during contraction.

"These findings are remarkable because they indicate that we can influence the function of the body's immune system in a drug-free, non-invasive way," said team member Conor Walsh.  "This provides great motivation for the development of external, mechanical interventions to help accelerate and improve muscle and tissue healing that have the potential to be rapidly translated to the clinic."

So I think I need to schedule a massage.  With luck and diligence, maybe I can get back out on the trail soon.  I certainly hope so; running is a real pressure-valve for me emotionally, and if I'm stuck on the sidelines until next summer like last time this happened, I'm gonna go out of my ever-lovin' mind.

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As someone who is both a scientist and a musician, I've been fascinated for many years with how our brains make sense of sounds.

Neuroscientist David Eagleman makes the point that our ears (and other sense organs) are like peripherals, with the brain as the central processing unit; all our brain has access to are the changes in voltage distribution in the neurons that plug into it, and those changes happen because of stimulating some sensory organ.  If that voltage change is blocked, or amplified, or goes to the wrong place, then that is what we experience.  In a very real way, your brain creates your world.

This week's Skeptophilia book-of-the-week looks specifically at how we generate a sonic landscape, from vibrations passing through the sound collecting devices in the ear that stimulate the hair cells in the cochlea, which then produce electrical impulses that are sent to the brain.  From that, we make sense of our acoustic world -- whether it's a symphony orchestra, a distant thunderstorm, a cat meowing, an explosion, or an airplane flying overhead.

In Of Sound Mind: How Our Brain Constructs a Meaningful Sonic World, neuroscientist Nina Kraus considers how this system works, how it produces the soundscape we live in... and what happens when it malfunctions.  This is a must-read for anyone who is a musician or who has a fascination with how our own bodies work -- or both.  Put it on your to-read list; you won't be disappointed.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

A winning smile

I've been told I have "resting scowl face."  I can't tell you the number of times I've been walking down the hall in the school and a student has said, "Boy, you look pissed off," or at the very least, "He's on a mission."

It gets worse when I'm concentrating.  My wife has told me that when I'm performing with my band, I have a knitted brow and that my eyes look... "intense."

She always tries to phrase things kindly if she can.

The odd thing is that I honestly enjoy performing, so it's not that I'm having a bad time.  I have a hard time explaining why I do scowl so much of the time, because I'm really not an angry person.

Really.

On the other hand, I just realized I was scowling when I wrote that.

The reason all this comes up is some recent research into the connection between facial expressions and endurance while running. Noah E. Brick, Megan J. McElhinney, and Richard S. Metcalfe, in a paper called "The Effects of Facial Expression and Relaxation Cues on Movement Economy, Physiological, and Perceptual Responses During Running" that appeared in the Journal of the Psychology of Sport and Exercise last month, found that deliberately relaxing your facial muscles and smiling while on a run actually helps you to move with more economy, resulting in less discomfort and an overall improvement in performance.

As a runner, I found this fascinating.  I'm sure, given that I scowl a large percent of the time anyway, that I must look positively furious while I'm running.  I don't have much photographic evidence of that, however, because there's a natural tendency to mug for the camera when you pass a race photographer.  But I honestly can't imagine the smile lasting for much more than a second or two after the shutter clicks.

What is coolest about this is that the researchers didn't just ask runners for their perceptions before and after, they had them breathe through a mask that measured their oxygen uptake (a good measure of the efficiency of your muscles).  They had four groups -- one that maintained a neutral expression, one as genuine a smile as you can muster under those conditions, one that was instructed to scowl, and one that concentrated on relaxing their entire upper body.  (The last-mentioned group was instructed to pretend that "they were holding a crisp with both hands while they were running and trying not to break it.")

Okay, so maybe I don't scowl the whole time.

The results were astonishing.  The smiling group was 2.8% more efficient than the scowling group, and 2.2% better than the neutral group.  (The relaxed group fell in between the two.)  While this may not seem like much of an improvement, it's equivalent to six weeks of consistent jump training (plyometrics).  And, I might add, it's a hell of a lot more pleasant.  The authors write:

The improved RE [respiratory efficiency] is toward the lower end of the 2%–8% reported for short-term training modes (e.g., Moore, 2016) but is greater than the smallest worthwhile change for RE (2.2%–2.6%) suggested by Saunders, Pyne, Telford, and Hawley (2004).  As such, the improved RE can be considered a real and worthwhile change.  Furthermore, the lower VO2 when smiling is equivalent to the 2%–3% improvement noted by Turner, Owings, and Schwane (2003) following six-weeks of plyometric training in distance runners, and the 1.7%–2.1% observed by Barnes et al. (2013) after 13 weeks of heavy resistance training in male cross-country runners.

So I'm gonna try it.  My first race isn't for a couple of months, given that we're still in the third of the seasons in upstate New York's "four-season climate" (the four seasons are: Almost Winter, Winter, Still Fucking Winter, and Road Construction) and the roadsides are covered with a nice layer of dirty slush.  But I can always try it while I'm training on the treadmill at the gym, although it might make my gym buddy wonder what's wrong with me.

What I find most fascinating about this is to speculate about the cause.  You have to wonder if it's because our expressions are so tied to our emotions -- that perhaps wearing a scowl puts your body on alert for danger, resulting in a combination of discomfort and an increase in adrenaline and the stress hormone cortisol (which would boost the rate at which you burn fuel without necessarily giving you anything back in the form of speed or endurance).  That's all just guesswork, however.

In any case, it's worth a shot.  So if you see a skinny blond guy running down the road in upstate New York wearing a goofy grin, I'm not high, I'm just running an experiment.  Literally.

Enter the Sandman

I've been fascinated with sleep ever since I can remember, and that's mostly because I've been a terrible sleeper ever since I can remember.  I'm one of those people who drifts off thirty seconds after my head hits the pillow, then wakes up at two AM with my mind spinning and can't get back to sleep for three hours.  All well and good on summer break, when I can take an afternoon nap if I need to, but it plays hell with my alertness and general mood during the school year.

Things have gotten a little better since I got a CPAP machine last year -- turns out I have obstructive sleep apnea due to a "narrow tracheal opening" (I have none of the other risk factors).  It was serious, too.  When I got the results of my sleep study, I was told that I was waking up an average of 23 times an hour.  Yes, that means that in an average eight-hour night, I was waking up over 180 times.

No wonder I was perpetually exhausted.

Since getting on a machine to regulate my breathing, it's gotten better, but I still am prone to wee-hours wakefulness and being tired in the middle of the day.  Annoying, but a malady I share with a lot of people, apparently.  And I've always wondered, what's sleep for, anyway?  What can possibly be so important that we slumber away on the order of a third of our life?

[image courtesy of photographer Evgeniy Isaev and the Wikimedia Commons]

The answer is: we don't know.  Evidently it's something not unique to humans -- virtually every animal species studied sleeps, and the more complex the brain, the more sleep they need.  There are hypotheses that sleep helps to reset the sensitivity of neurotransmitter receptors, that it allows consolidation of memories, that it facilitates the removal of toxic waste products from brain cells.  All are, at the moment, unproven.

All that's known is that when people are deprived of sleep for long enough, they kind of go off their rockers.

So it was with great interest that I read a paper last week in Nature called "Operation of a Homeostatic Sleep Switch" by Gero Miesenböck of Oxford University et al.  The research team studied sleep mechanisms in fruit flies:

Sleep disconnects animals from the external world, at considerablerisks and costs that must be offset by a vital benefit.  Insight into this mysterious benefit will come from understanding sleep homeostasis: to monitor sleep need, an internal bookkeeper must track physiological changes that are linked to the core function of sleep.

Miesenböck was interviewed by Sarah Kaplan of The Washington Post and described how an experiment on fruit flies could elucidate mechanisms of sleep in other animals:

Think about it.  We do it.  Every animal with a brain does it.  But obviously it has considerable risks...  If evolution had managed to invent an animal that doesn’t need to sleep... the selective advantage for it would be immense.  The fact that no such animal exists indicates that sleep is really vital, but we don't know why.

In order to study this response, Miesenböck's team used fruit flies that were genetically engineered for specific proteins to be switched on and off by laser light.  In particular, these flies had an artificial switch in their dorsal fan-shaped body (dFB), a cluster of cells that is known to be correlated with sleep.

They used the laser switch to release dopamine into the dFB, which suppresses activity in those cells, causing sleeping flies to immediately wake up.

In particular, there was one gated-channel protein that was off when the flies were sleeping and on when the flies were awake.  If the scientists turn the channel off permanently...

... the flies go into an unending sleep state.

It's like the stuff of fairy tales, except that there's no Prince Charming of the Fruit Flies.

The channel has been nicknamed "Sandman," for obvious reasons.  "It's beautiful, the self-correcting logic of the feedback mechanism," Miesenböck said.  "It's one of those things that gives you goose bumps when you see how it actually works because it's so, so unexpectedly simple and elegant."

An open question is whether the flies that can't wake up will live longer, since sleeping less is correlated with a shortened life span (both in fruit flies and in humans).  Miesenböck wasn't too fond of the idea of lengthened lifespan at the cost of never being awake, however.  "I don’t know if I would like to live longer if I am asleep most of the time," he said.  "I don’t know what the difference would be from being dead.  Anyway, it's getting philosophical now."

This research, however intriguing, is only the first step.  Whether humans have an analogous system is unknown -- as brain complexity increases, you might expect that the control systems would increase in complexity as well, but that's only a guess.  A complex switching system would likely engender more ways that it can fail.

After all, we don't see many insomniac fruit flies.

On the other hand, I'd love one of those laser-operated reversible sleep switches.  Switch on sleep at 10 PM, and have the "on" switch hooked up to my alarm clock.  Certainly preferable to tossing and turning for hours, although I do have to wonder what I'd do if the power went out in the middle of the night.

Oversleep, is my guess.

this mysterious benefit will come from understanding sleep

homeostasis: to monitor sleep need, an internal bookkeeper must

track physiological changes that are linked to the core function

of sleep

1

risks and costs that must be offset by a vital benefit. Insight into

this mysterious benefit will come from understanding sleep

homeostasis: to monitor sleep need, an internal bookkeeper must

track physiological changes that are linked to the core function

of sleep

1

Sleep disconnects animals from the external world, at considerable

risks and costs that must be offset by a vital benefit. Insight into

this mysterious benefit will come from understanding sleep

homeostasis: to monitor sleep need, an internal bookkeeper must

track physiological changes that are linked to the core function

of sleep

1