Name: 恐龙有吸血的敌人（Dinosaurs Had a Bloodsucking Enemy）
Uploaded: 2021-05-13T12:34:12.000Z
Duration: 5 min
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

This week on SciShow News, we're talking about bugs and brains.

程度副詞

Except… not really true bugs, just some arachnids.

But “arachnids and brains” didn't sound as catchy.

Anyway, in a paper published this week in Nature Communications, scientists found two

separate clues that teach us a little more about dinosaurs and their parasites.

For one, these researchers discovered an extinct tick entangled in a piece of a dinosaur feather.

This sample was trapped in a 99-million-year-old chunk of amber from Myanmar, and dates back

The big news here isn't the feather itself, though.

Because finding ticks preserved with direct evidence of what they fed on is really rare.

In fact, this is the oldest known example.

The bit of feather is about two centimeters long and includes more than 50 barbs along

It's pretty similar to modern-day bird feathers, but a whole range of dinosaurs from the Cretaceous

period had feathers like this, including ground-running dinos and more bird-like species.

So we don't know exactly what kind of dinosaur the tick was feeding on, but since this was

before modern birds existed, we can definitely rule them out.

And that one species wasn't alone in its taste for dinosaur blood.

This paper also looked at a separate piece of amber from the same period, with /indirect/

evidence that a different extinct tick was also a dinosaur parasite.

These ticks weren't all tangled up in feathers, which is why it's indirect evidence.

One was full of blood, and another pair of two ticks were preserved close together.

The pair had some other junk on them, too — these hair-like structures called setae

This family of beetles is still around today and some species like to hang out in bird

nests, eating stray bits of feathers and skin... all that delicious stuff.

We know some dinosaurs built nests too, so both the ticks and beetles were probably living

The researchers also say that a drip of plant resin would be more likely to trap two unfed

ticks at once if they were hanging out in a nest together.

But, Jurassic Park aside, we won't be able to clone a feathered dinosaur from blood in

No one's ever actually extracted DNA from insects preserved in amber — there are just

too many things that can go wrong or break down.

So for now, that's still the stuff of sci-fi.

But our second topic is something that happens to humans all the time.

Picture this: you're walking down the sidewalk when you realize that, right where your foot

You see it there, and you desperately try to adjust, but you know... plop.

You're weight is going down any way and... it's happened

But a group of researchers from Johns Hopkins University may have figured out why it's

so hard to stop doing something while your body is in motion.

Previously, scientists thought that only one region of the brain — part of the prefrontal

cortex — was involved in sending that last-minute “stop!” signal after the brain directs

But now we know that getting this signal out actually requires super-fast coordination

between two different parts of the prefrontal cortex, plus part of the premotor cortex.

To figure this out, scientists gave 21 human subjects and one macaque monkey mostly similar

tasks while taking a peek at what their brains were doing.

The humans had their brain activity monitored with fMRI, which measures general blood flow

And the monkey had electrodes implanted in its brain to monitor some individual neurons.

We didn't do that to the people... because we didn't want to cut their brains open.

In the main test, the subjects saw one of two shapes on a computer screen, which told

them whether blue was going to mean go and yellow was going to mean stop, or vice versa.

Then, a black circle would pop up, and the study participants would quickly move their

But if a blue or yellow dot appeared, they would have to either stop or keep going with

their eye movement, depending on that initial shape and its meaning.

A previous version of this experiment used a simpler task.

But doing it this way let the researchers estimate signals related to different parts

of it, like watching for the shape on the screen versus sending the message to stop

The data suggest that one part of the prefrontal cortex identifies and interprets information

signals, and another part registers the intent to stop the motion.

Both regions seem to coordinate with another brain region in the premotor cortex, which

And whether they successfully stopped or not or not depended on the timing.

The researchers calculated that if a subject's decision took more than about a quarter of

a second, then the original “move!” signal was already on its way to the muscles and

They even suggest that this could help explain why people might stumble more as they get

older — aging brains communicate more slowly, so they might not be able to put on the brakes

But, as always, there's a lot more research left to do.

Thanks for watching this episode of SciShow News, and thanks especially to all of our

patrons on Patreon who make this show possible.

If you want to help us keep making videos like this for the whole world for free, you

And don't forget to go to youtube.com/scishow and subscribe!