Researchers at the Karolinska Institutet in Sweden have discovered what amounts to a reflexive negativity bias in our sense of smell, showing that bad smells are processed rapidly and unconsciously. The olfactory bulb can process and send a signal to the motor cortex in 300 milliseconds, alerting us to rotten food before we swallow or of the presence of predators. The processing speed is much faster for smells that alert us to danger than for those with positive connotations.

Meanwhile, we tried a new trail last week only to realize that a family of bears must be using it daily—and why.

another trail
downwind of the dumpsters
bear scat

Honestly, I can’t quite wrap my head around this week’s sciku article. The role of dopamine in our external rewards system has been studied extensively, but we also have regular passive spikes of the neurotransmitter cycling trough our brains spontaneously—in mice it’s a spike every minute or so—and we don’t really understand why.

In a study published this week in Current Biology, researchers demonstrated that mice are not only responding to these regular spikes, but are able to alter them. The suggestion is that it might play a role in the foraging process, with a tiny dopamine hit every minute reminding them to stay alert for some greater reward. The chemical process seems to prod us forward, making sure we’re never quite satisfied. I wonder if it might play a role in ADHD?

At least that was my interpretation. The press release doesn’t quite make sense to me, and the study itself was even more impenetrably written. But I think that’s what it means? Maybe I just need a nap.

summer breeze
chipmunks forage
under my hammock

Who knew that the moon’s orbit wobbled on an 18.6-year cycle? Well, actually, we’ve known about this since 1728—and Bronze Age peoples knew about it thousands of years ago, and tracked it in their megalithic monuments all over the world.

But a paper in Nature Climate Change this week studied the impact it will have on high tide flooding in the coming decades. Right now we’re approaching the major standstill, where tides variation is the lowest, hiding the impacts of sea level rise on coastal flooding. In 2034, we’ll be at the minor standstill, which exacerbate the flooding.

he tells it again
walking home from the bar—
wobbly moon

cr: Andrew Johnson via Unsplash

In a study out of Yale this week, researchers explored the neurological pathways governing a fly’s choice in what to eat—is it the taste or the calories they’re after?

To explore this, scientists laced a normally sweet, nutritious food with bitter quinine, and watched the flies brains as they decided whether to eat that, or another food that was sweeter, but lower in calories.

In the end, it mattered how hungry they were. If the flies were hungry, they chose the bitter food with more calories, but if they were satiated they chose the sweetness, suggesting even in a fly there are multiple pathways governing these decisions—the gut’s needs can override the brains dopaminergic reward system.

While it’s not mentioned in the study, I can’t help but think this is the answer to the mystery of why artificial sweeteners don’t help people lose weight. Diet soda satisfies the reward system with a hit of sweetness, but does nothing for the body’s deeper craving for calories. So we drink diet soda, then eat more, and it makes no difference to calorie intake.

This doesn’t mean we aren’t better off drinking diet soda, as simple sugars are inflammatory at these high doses, and lead to diabetes and other health problems—and are kind of the opposite of chemotherapy, when you think about it, feeding tumor growth. But don’t expect to lose weight.

fruit flies
descending
on fallen fruit

I almost forgot to share this week’s sciku! It was inspired by researchers at Stanford and TU/e who have been studying how hummingbirds hum.

If you’ve spent any time watching hummingbirds, you might already know they answer: they don’t fly like regular birds that apply aerodynamic force to the undersides of their wings with every down-stroke. Their wings move back and forth horizontally, letting letting them hover like a helicopter. This motion creates pressure fields on both the up and the down strokes, and those fields of compacted air oscillate back and forth at 40 hertz, creating their iconic and soothing hum, rather than an annoying buzz.

What was interesting about this story, though, was the great pains the researchers went through to record the hummingbirds and then process the data. Over the course of four days, they filmed with 15 high speed cameras, over two thousand microphones in a “sound camera” array, and recorded the movement of air with a series of pressure plates. Then it took THREE YEARS of machine learning AI to process and synchronize the massive amount of data that was collected.

There’s a cliched joke about scientists wasting time and grant money studying whale burps or the way cheese melts on toast. But it’s often the challenges that come with solving any problem—even a mundane problem—that lead to new advances. In this case, the sound camera technology that was developed will be used to decrease the background noise created by drones and fans, and ultimately could make all of our appliances quieter. Wouldn’t that be nice?

hummingbird
heavy in the field
of sound